A Field Guide and Key to the Genus Melissodes in Oregon (Hymenoptera: Apidae)

Introduction

Melissodes Latreille is a common genus of wild bees from the tribe Eucerini occurring in the New World (Laberge, 1956a; Laberge, 1956b; Laberge, 1961; Wright et al., 2020). As of now, a total of 129 species have been described in this genus making it the second largest in the Eucerini tribe (Wright et al., 2020). 26 of these species have been documented in Oregon (see table 1) and 8 have known ranges that overlap portions of Oregon (see table 2). Melissodes are known to be important pollinators in crops such as cotton (LaBerge, 1956), alfalfa (LaBerge, 1956), muskmelons (Winfree, et al., 2007), watermelon (Campbell et al., 2018; Winfree, et al., 2007), canola (O'Brien & Arathi, 2018), and coffee (Ngo et al., 2013), but most chiefly so in sunflowers (Parker et al., 1981). Parker (1981) documented that a species of Melissodes (M. agilis) is a more proficient pollinator in sunflowers than that of the western honeybee. Although their importance has been expressed in agricultural settings (Parker, 1981) and likely in wild ecosystems due to their abundance (Laberge, 1956a), identification of Melissodes beyond genus is often scarce due to the subtle characters that differentiate between species. The genus was last revised in a three-part series by W. E. Laberge (1956a; 1956b; 1961) as well as a later correction to the M. (Callimelissodes) subgeneric key (Laberge, 1963), in which detailed species-specific treatments, generic and subgeneric keys, and distributions were first presented, representing a cornerstone for current-day Melissodes knowledge. However, the keys presented in these revisions can be, at times, slightly ambiguous and overwhelming due to the sheer number of species and intraspecific variation. As a genus, Melissodes are widespread and range over the entirety of the New World, but species differ largely in what areas they occupy (Laberge, 1956a; Laberge, 1956b; Laberge, 1961; Wright et al., 2020). Many species are restricted to South America and Central America, which, when trying to identify North American species using a key designed to include all 129 species, drastically inflates the amount of information needed to identify an individual. The same can be said for species whose ranges are restricted to specific portions of North America that differ from the location in which a specific individual was found. Herein, a key developed from that of Laberge (1956a; 1956b; 1961; 1963) using the same structure and traits but incorporating subgeneric splits and only including species who occur, or are likely to occur, in Oregon is presented. Although using a regional key such as this may not yield new state records for Oregon, apart from those whose ranges overlap this area and are included in the key, it may assist in ease of identification beyond genus allowing for species-level studies and less chances for drastic misidentification due to individual variation. Along with this, species descriptions and comparisons, derived from that of Laberge, (1956a; 1956b; 1961) are given to further aid in identification.

Table 1. A table of Melissodes species with their citations to the resource which documents their occurance in Oregon.

Species	Citations
Melissodes agilis	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Best et al., 2022a; Texas A&M University Insect Collection, 2023; Best, 2026; Illinois Natural History Survey, 2026; The International Barcode of Life Consortium, 2026)
Melissodes ablusus	(DeBano et al.)
Melissodes bimatris	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; MT James Entomological Collection, Washington State University, 2026; The International Barcode of Life Consortium, 2026)
Melissodes clarkiae	(Laberge, 1961; Best et al., 2022a; Bentley & Osborn, 2026; Best, 2026; The International Barcode of Life Consortium, 2026)
Melissodes communis	(Laberge, 1956a; Ikerd, 2019; Johnson, 2020; Best et al., 2022a; Ikerd & Engler, 2023; Bentley & Osborn, 2026; Best, 2026; The International Barcode of Life Consortium, 2026)
Melissodes dagosus	(Laberge, 1956b; Ikerd, 2019; Ikerd & Engler, 2023; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; The International Barcode of Life Consortium, 2026)
Melissodes glenwoodensis	(Laberge, 1961; Ikerd, 2019; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; The International Barcode of Life Consortium, 2026)
Melissodes lupinus	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Graham et al., 2021; Best et al., 2022a; Ikerd & Engler, 2023; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026; The International Barcode of Life Consortium, 2026)
Melissodes lustrus	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Best et al., 2022a; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026)
Melissodes lutulentus	(Laberge, 1961; Ikerd, 2019; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026)
Melissodes menuachus	(Laberge, 1961; Ikerd, 2019; Illinois Natural History Survey, 2026)
Melissodes metenuus	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Graham et al., 2021; Best et al., 2022a; Ikerd & Engler, 2023; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026)
Melissodes microstictus	(Laberge, 1961; Johnson, 2020; Best et al., 2022a; Ikerd & Engler, 2023; Texas A&M University Insect Collection, 2023; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026; MT James Entomological Collection, Washington State University, 2026; The International Barcode of Life Consortium, 2026)
Melissodes pallidisignatus	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Graham et al., 2021; Best et al., 2022a; Texas A&M University Insect Collection, 2023; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026)
Melissodes paululus	(Ikerd, 2019) Note, Laberge (1961) had Oregon within M. paululus’ range, just none had been collected.
Melissodes plumosus	(Laberge, 1961; Ikerd, 2019; The International Barcode of Life Consortium, 2026)
Melissodes pullatellus	(Laberge, 1961; Bentley & Osborn, 2026; Grinter et al., 2026)
Melissodes rivalis	(Laberge, 1956b; Ikerd, 2019; Johnson, 2020; Best et al., 2022a; Ikerd & Engler, 2023; Texas A&M University Insect Collection, 2023; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026; Motz, 2026; The International Barcode of Life Consortium, 2026)
Melissodes robustior	(Laberge, 1961; Ikerd, 2019; Best et al., 2022a; Bentley & Osborn, 2026; Best, 2026; Johnson, 2026; MT James Entomological Collection, Washington State University, 2026; The International Barcode of Life Consortium, 2026)
Melissodes saponellus	(Laberge, 1961; The International Barcode of Life Consortium, 2026)
Melissodes semilupinus	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; The International Barcode of Life Consortium, 2026)
Melissodes stearnsi	(Laberge, 1961; Bentley & Osborn, 2026; The International Barcode of Life Consortium, 2026)
Melissodes subagilis	(Laberge, 1961; Ikerd, 2019; Johnson, 2020; Illinois Natural History Survey, 2026)
Melissodes tepidus	(Laberge, 1956a; Ikerd, 2019; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026)
Melissodes tristis	(Ikerd, 2019)
Melissodes utahensis	(The International Barcode of Life Consortium, 2026)

Table 2. A table of Melissodes species with their citations to the resource which documents their ranges which overlap Oregon (i.e. species with a likely occurance in Oregon that have yet to be documented).

Species	Citations
Melissodes bicoloratus	(Ikerd & Engler, 2023)
Melissodes compositus	(Ikerd, 2019)
Melissodes druriellus	(Ikerd & Engler, 2023)
Melissodes grindeliae	(Laberge, 1961)
Melissodes minusculus	(Ikerd, 2019)
Melissodes nigracauda	(Washington State Department of Agriculture, 2025; MT James Entomological Collection, Washington State University, 2026). Likely the same specimen.
Melissodes verbesinarum	(Laberge, 1961; Ikerd, 2019; MT James Entomological Collection, Washington State University, 2026)
Melissodes vernalis	(Laberge, 1961)

How to use this resource

This field guide is designed to aid in identifying Melissodes species in Oregon. This includes comparisons of similar genera such as Eucera and Diadasia, which have overlapping ranges and similar morphologies, comparisons of similar species within the genus, and regional keys. Ranges have been determined using historic taxonomic literature in tandem with GBIF occurrence records (see tables 1 & 2). This data was also used to evaluate distributions, phenology, and host-plant relationships. Each species has a full treatment used to assist in identification, locality, morphology, and more (species treatments are outlined below).

Species treatments

Each species description consists of what follows: Morphological descriptions, particularly of key diagnostic features with accompanying photos of the feature; distribution maps plotted in Leaflet using OpenStreetMap (OSM) derived from authoritative taxonomic literature (Laberge, 1956a; 1956b; 1961) and recent sampling from GBIF occurrence records to produce an up-to-date range; phenological graphs created using data from GBIF occurrence records; flower records and/or preference if lists are too extensive; when applicable, notes concerning taxonomic history and/or distinctive identifiers; two "Feild Marks" and "Similar species" sections (one per sex given the sexual diamorphism) unless stated otherwise; a similar naming convention to that used by the North American Native Bee Collaborative (2020) will be adapted for this guide, that being at the beginning of each species treatment, a group-name is given to species of similar morphologies (if a group-name is absent, then the species does not specifically resemble another and instead, the word “distinct” will take the place of group-name). For most species, as there is insufficient data, phenological graphs will consist of two lines, one representing phenology based on Oregon captures, and the other based on captures across each species respective range. Each species "Field Markers" section is based on the information given about both sexes from the genus treatment; if not familiar with Melissodes as a genus, reading the genus treatment is recomended before subsequent species treatments. Morphological descriptions for each species are derived from that of Laberge (1956a; 1956b; 1961). Precursing each of the species treatments, the genus will be treated. This will not include a group-name as no other genera are described within this guide; similar genera will be listed instead.

Note: according to The International Barcode of Life Consortium (2026), M. micheneri, M. personatellus, and M. utahensis have been found in Oregon (once per species except the latter). However, the two former species are omitted in this field guide above as the only identifying features are DNA barcodes and their current known ranges (without these datapoints) do not overlap or include Oregon. M. utahensis, the sole exception to this rule, is included in Table 1 as three records, all from largely differing areas of Oregon, have been collected and for the reasons outlined in its species treatment. Although M. micheneri and M. personatellus may have been collected in Oregon, the lack of sufficient data in regards to their identification methods, as well as Oregon being vastly out of their range, makes it challenging to be certain (see more in the M. utahensis species treatment).

Reference Images

As can be determined below, subtle differences are used in delimiting species of Melissodes. To describe these delimiting characters, terms have been applied to specific anatomical features and structures. Below is a list of Melissodes images with labeled anatomical features, the terms used to describe these features will be used throughout the guide; definitions for these terms are also in the glossary with parenthesized use cases.

Fig. 1. Fig. 1. An illustration of the dorsal metasomal structure of a female Melissodes that has been redrawn and relabeled from that of Laberge (1956a). Only the first tergum is regionally labeled, but T2-T6 follow the same patterns (male Melissodes have 7 terga). Originally presented as "Fig. 20. Diagram of metasoma (approximately X 11) of M. communis showing areas of vestiture. Regional terms are on the left and descriptive terms referring to vestiture are on the right. Similar types of shading indicate similar types of pilosity."

Fig. 4. Diagrams representing the leg anatomy of a Melissodes. One diagram per sex is given due to their sexual diamorphism.

Fig. 5. Wings of a Melissodes (cells shown by capital letters). Cells: A, anal; D, discoidal: MC, marginal; MD, median; SM, submarginal; SMD, submedian.

Fig. 6. Labeled images illustrating the ventral structure of a Male Melissodes' metasoma. The sterna are labeled S1-S6; note that this is a male, females have only 5 sterna.

Identification

Because of their sexual diamorphism, two keys for the species of the genus Melissodes in Oregon are listed below (male and female keys). These keys are developed from those of Laberge (1956a; 1956b; 1961; 1963), but include subgeneric splits and only Melissodes that are known to inhabit, or have ranges that overlap, Oregon. If a couplet regarding a certain character seems ambiguous, check morphologically similar species in their respective treatments.

Key to the bees of the genus Melissodes in Oregon

Males

1. The fourth sternum and often third sternum’s posterior margins are either widely convex, or developed into a thin, broad, colorless hyaline flap. Go to 2

The fourth and third sterna’s posterior margins are either straight or slightly concave, but either way, they never develop into a flap. Go to 12

2. (1) The fourth sternum’s posterior apical area is developed into a thin, broad, colorless hyaline flap that’s the same length of the rest of the sternum medially and is medley weakly emarginate. The second sternum is widely convex and the apical area is hyaline. The third sternum has a hyaline, bilobed, wide flap that is similar to the second sternum, although the flap is shorter. The fifth sternum is the same as the second. The clypeus is usually white to cream-colored and on rare occasions, sometimes pale yellow ... stearnsi

The fourth sternum’s posterior apical area isn’t developed into a thin, broad, colorless hyaline flap, but it is widely convex and weakly medially emarginate. Sterna two and five have faintly convex to straight apical margins and the third sternum has a convex to nearing straight apical margin. The clypeus is yellow, cream-colored, or white. Go to 3

3. (2) F4-F10 have longitudinal depressions on the outer surface that are shallow, narrow, and shiny. Usually, F3 and F11 have partially developed depressions as well. Go to 5

F5-F9 have longitudinal depressions on the outer surface that are shallow, narrow, and shiny. At most, F10 also has a developed depression, however F11 does not. Go to 4

4. (3) The first flagellar segment’s minimum length is more than one-fourth of the second segment’s maximum length. The flagellum has no segments that have shallow narrow depressions laterally. However, the flagellar segments might have some flattened areas. The galeae are matte and dulled dorsally due to regular, dense tessellation ... nigracauda

The first flagellar segment’s minimum length is less than, or equal to, one-fourth of the second segment’s maximum length. The galeae are usually shiny to dull dorsally. However, if the galeae are dull, then F1 is less than one-fourth of F2. There are at least a few flagellar segments that have shallow, narrow, longitudinal depressions on the lateral areas. Go to 9

5. (3) The length of the penultimate flagellar segment is two times its width or less. Go to 6

The length of the penultimate flagellar segment is longer than two times its width. Go to 8

6. (5) The galeae are matte and dull dorsally due to coarse, dense, and regular tessellation. The first flagellar segment’s minimum length is less than one-fifth of the second segment’s maximum length. Go to 7

The galeae are somewhat shiny to shiny dorsally but faintly dulled due to delicate reticular shagreening; the surface has no tessellation. F1’s minimum length is more than one-fifth of F2’s maximum length ... clarkiae

7. (6) The hairs on the sixth and seventh terga are mostly brown and the hairs on the basal half terga 3-5 are mostly brown as well … ablusus

The hairs on the sixth and seventh terga are white to gold-colored and the hairs on the basal half of terga 3-5 are pale brown to ochraceous … minusculus

8. (5) The apical areas of the second and third terga have simple, erect to suberect hairs and the galeae are often shiny without shagreening or delicately reticularly shagreened. The third flagellar segment usually has a well defined ventrolateral depression. Go to 11

The apical areas of the second and third terga are glabrous and the galeae are often shagreened dorsally. The third flagellar segment usually does not have, or has a poorly defined and short, ventrolateral depression. Go to 10.

9. (4) The apical areas of the second and third terga have suberect hairs and the galeae are often dull due to dense shagreening. The first flagellar segment’s minimum length is usually less than one-fifth of the second segment’s maximum length ... lupinus

The apical areas of the second and third terga are glabrous as well as impunctate and the galeae are either shiny or dull due to shagreening. The first flagellar segment’s minimum length is usually less than, or equal to, one-fifth of the second segment’s maximum length ... glenwoodensis

10. (8) The interband zones of the second and third terga have round, deep, abundant punctures that are mostly separated by noticeably less than a single puncture diameter. The eyes are often greenish blue to blue … compositus

The interband zone of the third tergum, and usually the second as well, have their punctures that are mostly separated by one puncture diameter, and several that are separated by 2 to 3 puncture diameters. The eyes are often yellowish green to green … lustrus

11. (8) The galeae are dorsally shiny and unshagreened, or if shagreened, then delicately so on less than, or equal to, the apical half. Sterna 2-4 are medially shiny and are delicately reticularly shagreened. The clypeus is coarsely punctate basally ... metenuus

The galeae are somewhat dull dorsally due to delicate distinct shagreening. Sterna 2-4 are only moderately shiny medially due to shagreening. The clypeus has small round basal punctures ... plumosus

12. (1) The first flagellar segment’s maximum length is approximately 0.4 times or more the maximum length of the second segment and the clypeus is distinctly protuberant, protruding beyond the eye by three-fourths of an eye's width in profile or more ... rivalis

The clypeus is usually protruding beyond the eye by three-fourths of an eye's width in profile or less or if it is, then the first flagellar segment’s maximum length is less than 0.4 times the maximum length of the second. Go to 13

13. (12) The first flagellar segment’s minimum length is notably longer than half the second segment’s maximum length, the pubescent bands on terga 2-5 are apical, and the pubescent bands on terga 2-5 are approximately the same width across each respective terga (not widening or narrowing) and each tergal band is approximately the same width as the other tergal bands ... dagosus

The first flagellar segment’s minimum length is equal to, or shorter than half the second segment’s maximum length, the pubescent bands on terga 2-4 aren’t usually apical, and the pubescent bands on terga 2-4 aren’t usually the same width across each respective terga (not widening or narrowing) and each tergal band isn’t usually the same width as the other tergal bands. These bands are often subapical and interrupted medially. Go to 14

14. (13) Terga 2-5 do not have any pale pubescent bands, or if there are pale pubescent bands, then they are all interrupted medially. However, if one or two of the pubescent bands are complete, then the labrum is almost, or entirely, pale or the thoracic hairs are mostly black to black and white mixed. Go to 16

Terga 2-5 usually have complete pale bands and on occasion one or more are interrupted. If there are only one or two complete bands, then the labrum is mostly, or all, black and thoracic hairs are bright rusty-red. Go to 15

15. (14) The last two tera have black to dark brown hairs. The labrum is entirely pale and the mandibles often have basal yellow macula. Go to 16

The last two terga only have pale hairs, or the labrum minimally is dark marginally and the mandibles usually do not have basal pale macula, or both of these two traits combined (mandibles can have maculations). Go to 17

16. (14 or 15) The second tergum’s wide distal pale band is equal to, or almost equals, the medial portion of the apical area. The fourth tergum’s wide pale band is more than, or equal to, fourth times the medial portion of the apical area ... tepidus

The second tergum’s distal band is narrow and equal to, or less than, one-half the width of the medial portion of the apical area. If the second tergum’s distal band is, or almost is, as wide as the medial portion of the apical area, then the fourth tergum’s pale band is clearly narrower than fourth times the medial portion of the apical area ... communis

17. (15) The labrum is entirely light-colored and has no brown apical margin. The mandibles have a large pale spot at their bases ... verbesinarum (in part)

The labrum usually has some dark colorations on its margin and the mandibles usually don’t have large basal pale spots. Go to 18

18. (17) The length of the penultimate flagellar segment is less than three times its width (maximum length and narrowest width) and the antennae does not surpass the pterostigma in repose. Go to 19

The length of the penultimate flagellar segment is equal to or more than, three times its width (maximum length and narrowest width) and/or the antennae surpass the pterostigma in repose. Go to 22

19. (18) The labrum and the mandibles are black and have no yellow maculations. When in repose, the antennae reach the pterostigma ... grindeliae (in part)

The labrum and usually the mandibles have some form of yellow maculations (mandibles can still be black but the labrum always has a macula). When in repose, the antennae usually do not reach the pterostigma. Go to 20

20. (19) The mandibular bases have yellow maculations ... pallidisignatus (in part)

The mandibular bases do not have yellow maculations. Go to 21

21. (20) The apical areas of terga 2-5 are opaque with a deep brownish red color. The basal areas of terga 4-6 are covered in reddish brown pubescence and hairs ... druriellus (in part)

The apical areas of terga 2-5 are colorless to testaceous or brownish yellow hyaline. The basal areas of terga 4-6 are covered in pale pubescence and hairs ... pallidisignatus (in part)

22. (18) The apical areas of the terga are completely, or almost completely, opaque (deeply infumate) and the clypeus is completely yellow apart from the tentorial depressions and apical margin ... druriellus (in part)

The apical areas of the terga are colorless hyaline or slightly infumate and translucent but not opaque. If the apical areas of the terga are, or almost are, opaque, then the clypeus is either partially or entirely black. Go to 23

23. (22) The first flagellar segment’s maximum length is more than one-third of the third segment’s minimum length. Go to 24

The first flagellar segment’s maximum length is less than, or equal to, one-third of the third segment’s minimum length. Go to 28

24. (23) The first tergum has an obvious and well developed distal band consisting of appressed or subappressed, dense, white pubescence that reaches and obscures the apical margin across the entire tergum (sometimes the apical band is worn). Go to 25

The first tergum doesn't have an obvious apical band of white, dense, hairs that obscure the apical margin, or if there are dense apical hairs present, then they only occur on the lateral areas and are equal to, or less than, one-third of the width of the entire tergum. If there is an apical band across the entire tergum, then it doesn’t medially obscure the apical area. Go to 26

25. (24) The mandibular bases have a yellow macula and the labrum is mostly yellow and has a darkened border. The first flagellar segment’s minimum length is usually more than, or equal to, one-third of the third segment’s maximum length ... semilupinus

The mandibular bases are black with no yellow maculations and the labrum is completely black, or sometimes has a small mediobasal pale macula. The first flagellar segment’s minimum length is usually less than one-third of the third segment’s maximum length ... bimatris

26. (24) The mandibular bases usually do not have a pale macula, or if there is a pale macula, then the scutellar and mesoscutal hairs are medially black. The galeae are dull due to dense shagreening ... robustior

The mandibular bases usually have a yellow macula and the mesoscutal hairs aren’t dark brown or black, or the galeae are shiny and not shagreened. Go to 27

27. (26) The labrum and bases of the mandibles are yellow and the mesoscutal and scutellar hairs aren’t dark medially ... menuachus (in part)

The labrum and the bases of the mandibles have no pale maculations and the mesoscutal and scutellar hairs are abundantly dark medially ... grindeliae (in part)

28. (23) The clypeus is entirely, or at least partially, black. Go to 29

The clypeus is entirely light excluding the dark spots denoting the tentorial depressions or the anterior notches and margin. Go to 31

29. (28) The clypeus is often partially yellow and the flagellar segments have a depressed or flattened shiny portion laterodorsally. The galeae are unshagreened and shiny above excluding the tips. All of the terga have opaque dark reddish brown to black apical areas; not hyaline ... paululus

The clypeus is partially or entirely black and the flagellar segments have no depressed or flattened shiny laterodorsal areas. The galeae vary in sculpture but are usually shagreened or tessellated above. All of the terga are hyaline apically. Go to 30

30. (29) The clypeus is completely black and usually has a shiny boss medially. The vestiture of the body is usually white. The antennae are very long and the underside of flagellar segments 2-11 are red with the last one or two flagellar segments being darker than the rest of the flagellar segments ... tristis (in part)

The clypeus usually has a yellow marking and the flagellum is entirely black excluding a small ventral pale macula ... microstictus

31. (28) The mandibular bases have a yellow macula and the labrum has a large mediobasal pale macula (at least equal to, and usually larger than, one-third of the labrum). Go to 32

The mandibular bases do not have a yellow maculation and the labrum does or does not have a mediobasal pale macula. Rarely do both the labrum and mandibular bases have pale macula, but if so, then the macula on the labrum is less than one-third of the area of the labrum and/or the macula on the bases of the mandibles are tiny. Also, rarely is the labrum black and the mandibular bases bearing tiny yellow macula. Go to 34

32. (31) The galeae are dulled above due to fine reticular shagreening and the wings are yellow to red. The hairs on the head and thorax are minimally pale ochraceous and often pale rusty-red ... agilis

The galeae are shiny above with no shagreening, except for the tips. If the galeae are shagreened, then the wing veins are black to brown or the thoracic and head hairs are white or white with dark brown mixed. Go to 33

33. (32) Larger bee, around 12-15 mm. long. The first flagellar segment’s maximum length is equal to, or almost equal to, one-third of the third segment’s maximum length, and the minimum length of the first flagellar segment is notably longer than the pedicel’s length on the same side ... menuachus (in part)

Small to medium sized bee, around 8-13 mm. long. The first flagellar segment’s maximum length is much less than one-third of the third segment’s maximum length, and the minimum length of the first flagellar segment is barely, if at all, longer than the pedicel’s length on the same side ... verbesinarum (in part)

34. (31) The punctures on the interband zone of the second tergum are extremely tiny and mostly separated by more than, or equal to, three puncture diameters; rarely any wider than the bases of the hairs that arise from them. The interband zone punctures of the third and fourth terga are also very tiny to small, indistinct, and shallow and mostly separated by two puncture diameters (usually separated by less on the fourth tergum). Go to 35

The punctures on the interband zone of the second tergum are larger and mostly separated by two puncture diameters or less; each puncture is notably wider than the bases of the hairs that arise from them. The interband zones of the third and fourth terga have large, deep, round punctures that are mostly separated by 1 puncture diameter. If the second, third, and fourth terga have tiny and largely separated punctures, then the bee is medium-sized and the wing veins are red to yellow. Go to 36

35. (34) The labrum often doesn't have a medial pale macula, or if it does, then the macula is less than one-third of the labral area. The galeae are dull above due to dense reticular shagreening and the pygidial plate is wide, with its width about two-thirds of its length ... utahensis

The labrum has a pale macula that is more than, or equal to, one-half of the labral area. The galeae are shiny and unshagreened above apart from the tips and the pygidial plate is often narrow, with its width often less than two-thirds of its length (usually less than one-half) ... vernalis

36. (34) The first tergum’s apical hairs are appressed, white, dense, plumose, and short creating a distinct band that reaches the apex across the entire tergum. The second tergum’s distal pale pubescent band is at least as wide, and usually widener, than the apical area. On occasion, the mesoscutum and scutellum have brown hairs ... lutulentus

The first tergum’s apical hairs are medially sparse and/or minutely barbed and only dense and plumose laterally. The second tergum’s distal pale pubescent band is usually narrower than the apical area. The dorsal areas of the scutellum and mesoscutum do not have dark hairs. Go to 37

37. (36) A medium-sized bee, approximately 11 mm. long and the galeae are shiny with no shagreening above apart from the tips. The apical area of the first tergum is obscured by hairs in the lateral one-thirds or faintly less but not obscuring the apical margin medially. The overall vestiture is extremely pale ochraceous to white ... bicoloratus

A smaller bee, around 9 to 11 mm. long and the galeae are often dull above due to shagreening, minimally in the apical halves and sometimes more. The apical area of the first tergum doesn’t have hairs obscuring it at lateral areas. The overall vestiture is often somewhat yellow to ochraceous ... subagilis

Females

1. In profile view, the clypeus protrudes beyond the eye by one-half to two-thirds of an eye’s width and the inner margins of the eyes are parallel to one another. The basitarsi’s inner surfaces have dark brown to black hairs, and the scopal hairs are usually yellowish and plumous … rivalis

In profile view, the clypeus protrudes beyond the eye by less than one-half of an eye's width. If the clypeus is protruding by one-half of an eye’s width, then the inner margins of the eyes are not parallel and instead converge toward the mandibles and/or the hind basitarsi’s inner surfaces have bright red to yellow hairs. The scopal hairs are sometimes branched weakly. Go to 2

2. (1) The pygidial plate is narrowly U-shaped and the scopal hairs are somewhat weakly branched, usually having one to two branches on either side of each rachis. Go to 8

The pygidial plate is often more V-shaped and has a rounded or acute apex. The scopal hairs are stronger and plumose with most consisting of three or more branches on either side of each rachis. Go to 3

3. (2) The second, third, and fourth terga have distal pale bands that are apical, approximately the same width across each terga (not narrowing or widening) and the same width to one another, and around as narrow, or narrower, than the basal dark pubescence. The hairs of these bands do not arise from noticeable punctures … dagosus

The second, third, and fourth terga, or at minimum just the second tergum, do not have distal pale bands that reach the apex across the entire tergum. If the bands reach the apex across the entire tergum, then they diffuse across it instead of making a clear apical band or the bands are much wider than that of the basal dark pubescence. Or the bands are not approximately the same width across each terga (narrowing and widening) and not the same width to one another. Or both of these combined. Go to 4

4. (3) The ultimate flagellar segment is slightly shorter than, or as wide as, its own width; approximately equal to the length of the penultimate segment. Or the bee is small, around 8-9 mm. long and has abundant long hooked galeal hairs above, or incredibly short blunt straight sparse galeal hairs and the galeae is densely regularly tessellated. Go to 8

The ultimate flagellar segment is longer than the penultimate segment and longer than it is wide. The bee is small to large, but if small, then the galeae are either not tessellated or the hairs are abundant straight and long. Never a small bee with abundant hooked galeal hairs. Go to 5

5. (4) The first tergum has sparse dorsal punctures that don’t surpass the basal one-third of the tergum medially, apart from a few widely spaced punctures. The galeae are shiny. The surfaces of the interband zones of the second and third terga are dull due to dense, fine, reticulo-transverse shagreening. The lateral portions of the thorax and propodeum have black hairs. Go to 8

The lateral areas of the thorax and propodeum have pale hairs. If the lateral areas of the thorax and propodeum have dark hairs, then the first tergum has dense punctures that reach the basal one-half or more, and/or the galeae are dull due to tessellation or shagreening. Sometimes the surfaces of the second and third terga’s interband zones are shiny with no shagreening. Go to 6

6. (5) The first tergum has very sparse dorsal punctures that do not surpass the basal one-third of the tergum, and often less than this. If this is the case (pale lateral mesepisternal hairs and tergal punctations as described), then either the bee is small to medium-sized and has an elongated somewhat U-shaped pygidial plate, with its sides approximately parallel to one another, that's around two times as long as it is wide medially. Or, a larger bee that has its hairs on the inner surfaces of the hind basitarsi black, and the hairs on the lower areas of the lateral surface of the mesepisterna are black. Go to 8.

The first tergum has abundant punctures that usually reach the basal half of the tergum and sometimes surpass it. If the punctures are very sparse and do not surpass the basal one-third of the first tergum, then the bee is medium-sized, its pygidial plate is shorter and V-shaped (in length, shorter than two times its width medially), and the hairs on the lower areas of the lateral surface of the mesepisterna are not dark. Go to 7.

7. (6) The sixth tergum’s postgradular carina is laterally lamelliform and ends abruptly in a blunt short denticle. The apical half of the pygidial plate is narrow and its sides are often somewhat parallel to one another unless the plate has been worn. The tibial plate is short and its edges show through the hair except on the lower anterior angle and anteriorly. Go to 8

The sixth tergum’s postgradular carina usually isn’t present laterally, or at most, is only cariniform not lamelliform and does not end in a denticle. The apical half of the pygidial plate is not narrowed and the sides are not parallel to one another; pygidial plate short and wide. The tibial plate is larger and the edge is obscured by hairs, minimally on the anterior half of the lower area, and sometimes more unless the hairs are worn. Go to 18

8. (2, 4, 5, 6, 7) The galeae have abundant long hooked hairs above and the second, third, and fourth terga are largely covered in short, pale, diffused, pubescence unless worn. The fifth and sixth terga have long, dark ochraceous to ochraceous medial hairs, and long white lateral hairs … stearnsi

The galeae have rather sparse, straight, short hairs and the second, third, and fourth terga are not largely covered in short, pale, diffused, pubescence. The fifth and sixth terga usually have dark hairs, minimally medially and sometimes more. Go to 9

9. (8) The scopal hairs are somewhat weakly branched, usually having one to three branches on either side of each rachis ... clarkiae

The scopal hairs are highly branched, having more than three branches on either side of each rachis. Go to 10

10. (9) The majority of the scopal hairs are dark brown, sometimes paler brown medially, and the metasomal hairs are mostly dark brown to black (sometimes there is a small amount of paler pubescence on the second tergum). The galeae have dense tessellation … nigracauda

The majority of the scopal hairs are yellow to white and only brown near the basitibial plate apical areas of the basitarsi. The galeae have varying sculptures. Go to 11

11. (10) The ultimate flagellar segment has a truncated appearance and is around as long as it is wide … lupinus

The ultimate flagellar segment has a more obliquely truncated or rounded appearance and is notably longer than it is wide. Go to 12

12. (11) The head hairs are entirely, or almost entirely, dark brown to black and the hairs on the inner surfaces of the hind bastitarsi and often the tibiae are dark reddish brown to black. The galeae are shiny to moderately shiny above with no, or very little, faint shagreening … metenuus

The head hairs are often pale apart from the abundant darker vertex hairs and the hairs on the inner surface of the hind bastitarsi and tibiae are usually pale-colored red to yellow. If the hairs on the head are mostly dark and the hairs on the inner surface of the hind bastitarsi and tibiae are dark, then the galeae are matt and dull above due to coarse tessellation. Go to 13

13. (12) The first tergum’s crowded basal punctures are restricted to, and do not surpass the, basal third or less medially. If the medial one-third of the first tergum has punctures, then they are mostly separated by more than two puncture diameters. The galeae are moderately shiny above, and delicately reticularly shagreened, but no dense tessellation. Go to 14

The first tergum’s crowded basal punctures usually extend to the basal half medially. The medial one-third of the first tergum has punctures that are mostly separated by one puncture width or less, minimally basally and sometimes more. The galeae are moderately shiny above, and delicately reticularly shagreened to regularly and densely tessellated. Go to 16

14. (13) The hairs on the inner surfaces of the hind basitarsi are black to dark reddish brown and the scopal hairs are usually yellow. The fifth and sixth terga have black to dark brown hairs or no white lateral tufts… glenwoodensis

The hairs on the inner surfaces of the hind basitarsi are red to yellow and the scopal hairs are pale ochraceous to white. The fifth and sixth terga have golden to pale brown medial hairs and large white lateral tufts of hairs. Go to 15

15. (14) The mesoscutal punctures positioned medially from the parapsidal line are often and/or mostly larger than those of the mesepisterna or scutellum, and mostly separated by less than, or equal to, one-half of a puncture diameter … compositus

The mesoscutal punctures positioned medially from the parapsidal line are irregularly sized, often and/or mostly smaller than the majority of those on the mesepisterna or scutellum, and mostly separated by more than one-half (several separated by more than, or equal to, two) of a puncture diameter ... lustrus

16. (13) The galeae are moderately shiny above, but somewhat dull due to faint reticular shagreening, notably so in the apical half or less … plumosus

The galeae are matte and dull above due to coarse, dense, regular tessellation. Go to 17

17. (16) The hairs on the inner surfaces of the hind basitarsi are black to dark reddish brown. The hairs on the head are entirely, or almost entirely, dark brown; minimally there are dark and pale hairs mixed on the face below the vertex … ablusus

The hairs on the inner surfaces of the hind basitarsi are dark red to dark brown. The hairs on the head are entirely white apart from the brown vertex hairs; there are no dark hairs below the vertex … minusculus

18. (7) The hairs on the ventral and lateral thoracic surfaces, including the propodeum, are dark brown. The second and third terga’s interband zones have irregular, large, piliferous, punctures on the lateral raised areas and the surfaces are shiny with no shagreening or tessellation. The surface of the supraclypeal area is shiny, smooth, and not shagreened. Go to 25

The hairs on lateral surfaces of the thorax are pale at least in some areas or the second and third terga’s interband zones are notably shagreened on the lateral raised areas. The surface of the supraclypeal area is often somewhat dull due to tessellation or shagreening. Go to 19

19. (18) In profile view, the eyes are narrower than the genal area. The widest portion of the eye in profile view is around less than, or equal to, half of its length. The hairs on the ventral and lateral thoracic surfaces are black. Go to 25

In profile view, the eyes are wider than, or equal to the genal area. The widest portion of the eye in profile view is usually more than half of its length, or the hairs on the lateral thoracic surfaces are entirely, or almost entirely, pale. Go to 20

20. (19) The length of the second flagellar segment is greater than its width ventrally and the hairs on the inner surfaces of the hin basitarsi are black to brown. Go to 25

The length of the second flagellar segment is less than, or equal to, its width ventrally, or the hairs on the inner surfaces of the hind basitarsi are yellow to red, or both of these combined. Go to 21

21. (20) The metasomal hairs are completely black to dark brown apart from the long basal hairs on the first tergum and sometimes a medial thin band across the second tergum. The dorsal area of the thorax has ochraceous to rufescent hairs. Go to 25

The metasomal hairs are never completely dark, except sometimes for the first and second terga, having varying arrangements and amounts of pale pubescence, or the dorsal area of the thorax has many dark hairs, or both of these combined. Go to 22

22. (21) The third tergum either has (1) its apical area covered/obscured, or nearly so, by a pale pubescent band apart from the medial triangular indentation that is less than one-third of the tergum’s width, or (2) is apical area impuncate and apubescent which either laterally narrows from the medial indentation, or is narrower across the entire tergum than that of the band on the second tergum. Go to 25

The third tergum either has (1) apical dark hairs across the medial one-third or more positioned posteriorly to distal pale band, or (2) apical pale hairs that do not entirely hide the surface and are weaker branched and more erect than the hairs of the distal pale band (if the hairs are worn, then punctures are visible), or (3) the apical apubescent area is wider than that of the second tergum’s distal pale band across the entire tergum. Go to 23

23. (22) The galeae are moderately shiny to dull above and shagreened to tessellated minimally in the apical half. Go to 24

The galeae are smooth and shiny above and not shagreened or tessellated except at their tips. Go to 25

24. (23) The metanotum is as long as, or longer than, the propodeum’s dorsal surface medially. The first tergum is usually only narrowly hyaline marginally, or not hyaline at all. If the first tergum is widely hyaline, then the clypeus doesn’t have a large median shiny boss and the hairs on the inner surfaces of the hind basitarsi are yellow to red. The second tergum’s distal pale band is often never medially interrupted and the anterior margin of this band is straight while the posterior margin is evenly curved. Go to 46

The metanotum is notably shorter than the propodeum’s dorsal surface medially or, either the first tergum is widely marginally hyaline, the hairs on the inner surfaces of the hind basitarsi are black to dark brown, and the clypeus has a large median shiny boss, or the second tergum’s distal pale band is medially interrupted or posteriorly notched marginally. Go to 25

25. (18, 19, 20, 21, 22, 23, 24) The terga do not have their pubescent bands complete but instead they are lateral fasciae, or sometimes entirely absent. If one of the tergal bands is complete, then it’s the second tergum’s band and the hairs on the lower lateral mesepisternal surfaces are dark brown. Go to 26

The terga have their pubescent bands complete on more than just one tergum. If however there is just one complete band on a single tergum, then it’s either not on the first tergum, or the hairs on the lower lateral mesepisternal surfaces aren’t dark. Go to 29

26. (25) The scopal hairs are entirely, or almost entirely fuscous (dark). Go to 27

The scopal hairs are mostly pale, but the hairs on the basitarsi are entirely, or mostly, dark brown. Go to 28

27. (26) A medium-sized bee, approximately 11-13 mm. long. The upper thoracic hairs (including those of the upper portions of the mesepisterna and posterior areas of the propodeum) are pale ochraceous to faintly rusty-red. The lateral and ventral thoracic hairs are black to dark brown … bicoloratus

A smaller sized bee, approximately 9-12 mm. long. The thoracic hairs are largely black to dark brown and sometimes there are a few paler hairs on the dorsal area of the propodeum, the periphery of the scutellum, and near the tegular bases … pullatellus

28. (26) The apical areas of terga 2-4 are glabrous, impunctate, translucent with reddish brown colorations, and shiny. The clypeus is not protuberant … druriellus (in part)

The apical areas of terga 2-4 are punctate, moderately dull due to coarse shagreening, or have appressed to subappressed hairs, or all of these combined. The clypeus sometimes protrudes beyond the eye by almost one-half of an eye's width in profile view … bimatris

29. (25) The length of the second flagellar segment is faintly, but notably longer than its width and the hairs on the inner surfaces of the hind basitarsi are are dark brown to brown. Go to 30

The length of the second flagellar segment is less than, or equal to, its width, and/or the hairs on the inner surfaces of the hind basitarsi are yellow to dark red. Go to 31

30. (29) The fifth and sixth terga have pale ochraceous to white lateral tufts of hairs. The mesepisterna have no dark hairs … menuachus

The fifth and sixth terga do not have pale ochraceous to white lateral tufts of hairs. The mesepisternal hairs are black to dark brown on the lower-lateral areas … semilupinus

31. (29) The apical area of the first tergum is widely colorless hyaline and the hairs on the inner surfaces of the hind basitarsi are black to dark brown. The overall vestiture is white to ochraceous and the clypeus has a median shiny boss … tristis

The apical area of the first tergum is often opaque, but if hyaline, then only narrowly hyaline or the hairs on the inner surfaces of the hind basitarsi are red to yellow, or the clypeus doesn’t have a median shiny boss. The overall vestiture is variable. Go to 32

32. (31) The apical area of the third tergum (1) has minimally dark hairs on the median one-third or more and sometimes these hairs are present across the entire tergum, or (2) has pale hairs, differing from those of the distal band in being more erect and less plumose, that don’t entirely obscure the surface, or (3) is glabrous, impunctate, and minimally wider than that of the medial width of the second tergum’s distal band. Go to 33

The apical area of the third tergum is obscured due to the distal band which reaches the apex across the entire tergum. If the third tergum’s apical area isn’t obscured by the distal band, then either (1) it’s glabrous, impunctate, and narrower than that of the second tergum’s distal band, or (2) it’s glabrous, impunctate, and widely triangularly shaped, although no wider than around one-third of the tergum’s width (this means that the distal pubescent band reaches the apical margin of the third tergum laterally but not medially). Go to 38

33. (32) The mesoscutum doesn’t have a dark brown to black patch of posteromedial hairs, or if so, then very few dark hairs are present. The clypeus often protrudes beyond the eye by about one-half of an eye’s width in profile. Go to 34

The mesoscutum clearly has a dark brown to black patch of posteromedial hairs. The clypeus rarely protrudes beyond the eye by one-half of an eye’s width in profile, almost always by less. Go to 35

34. (33) The first tergum’s apical impunctate area is medially longer than one-half of the punctate basal area. The overall vestiture is distinctly yellow to bright ochraceous … agilis

The first tergum’s apical impunctate area is medially equal to, or less than, one-half of the punctate basal area. The overall vestiture is fairly pale to pale ochraceous (not distinctly yellow/bright ochraceous) … bimatris (in part)

35. (33) The apical area of the second tergum is glabrous (sometimes very few dark, appresses, short hairs might be found near the posterior margin of the distal band), impunctate, and shiny with incredibly faint reticulotransverse shagreening. The interband zone of the second tergum is dull due to dense reticular shagreening (highly contrasts with the apical area sculpturing). The tegulae and vertex of the head bear abundant black to dark brown hairs. Go to 36

The apical area of the second tergum either has many suberect to appressed pale to dark hairs or punctures; surface is usually dull due to shagreening. If the apical area of the second tergum is glabrous, impunctate, and shiny, then the interband zone of the second tergum is shiny, not dull (does not contrast with the apical area sculpturing). The tegulae or the vertex or both usually don’t have dark hairs. Go to 37

36. (35) The distal band on the third tergum often reaches the apex of the tergum at extreme lateral areas and the pale hairs on the mesoscutum positioned anteriorly to the dark patch of hairs are pale ochraceous to white. The scopal hairs are ochraceous. The first tergum is reticularly shagreened and the punctures are small, distinct, and approximately separated by one-half of a puncture width … pallidisignatus (in part)

The distal band on the third tergum does not reach the apex across the entire tergum and is instead well-separated from it. The pale hairs on the mesoscutum positioned anteriorly to the dark patch of hairs are usually rusty-reddish. The scopal hairs are usually a golden-yellow color. The first tergum is densely reticularly shagreened and the punctures are incredibly shallow, large, and crowded. These punctures are usually obscured by the shagreening … druriellus

37. (35) The interband zone of the second tergum has punctures that are distinct, regular, and round across the entire tergum. The punctures might be more abundant laterally than medially … paululus

The interband zone of the second tergum is usually impunctate, or if there are punctures, then they are irregularly shaped and sized and indistinct or the punctures only occur on the lateral raised areas … robustior

38. (32) The apical areas of the second, third, and fourth terga are colorless to pale yellow-brown hyaline and the hairs on the inner surfaces of the hind basitarsi are red to yellow. Go to 39

The apical areas of the second, third, and fourth terga are piceous. If they are relatively translucent, then they aren’t pale yellow-brown, but instead opaque and dark brown. The hairs on the inner surfaces of the hind basitarsi are usually black to dark brown. Go to 40

39. (38) The mesoscutum has no, or very few, dark brown hairs. The hairs on the apical areas of the second and third terga are white, and the hairs across the fifth and sixth terga are ochraceous to white … saponellus

The mesoscutum has a large brown patch of hairs. The hairs on the apical areas of the second and third terga are dark brown, and the hairs across the fifth and sixth terga are usually dark brown as well … vernalis

40. (38) A smaller bee, the length of the forewing including the tegulae measures to be 7.0 to 8.5 mm. and the pygidial plate is V-shaped acutely. The flagellum is almost entirely black to dark reddish brown apart from a few dark red small ventral maculations of F3-F10. The distal pubescent band of the second tergum is narrowly interrupted, and the hairs on the inner surfaces of the hind basitarsi are dark … microstictus

A small to medium-sized bee, if the length of the forewing including the tegulae equals less than, or equal to, 8.5 mm., then the pygidial plate is apically rounded and not V-shaped acutely, or the underside of the flagellum is dark red, or both. The distal pale band of the second tergum usually isn’t medially interrupted, and the hairs on the inner surfaces of the hind basitarsi are red to yellow. Go to 41

41. (40) The interband zone of the second tergum is impuncate or essentially so and has erect to suberect dark hairs. The hairs on the inner surfaces of the hind basitarsi are black to dark reddish brown … grindeliae

The interband zone of the second tergum is distinctly punctate. If the interband zone is nearly impunctate, then the hairs are appressed to subappressed or pale, or both. The hairs on the inner surfaces of the hind basitarsi are usually red to yellow. Go to 42

42. (41) A medium-sized bee, the length of the forewing including the tegulae measures to be 9 to 10 mm. The lateral raised areas of the interband zone of the second tergum have distinct punctures. These punctures are of two sizes, some large and rather posteriorly directed, and the other that is tiny. The hairs on the inner surfaces of the hind basitarsi are dark brown … pallidisignatus (in part)

A smaller bee, if the length of the forewing including the tegulae is more than, or equal to, 9 mm., then the interband zone of the second tergum is impunctate or all the punctures are of similar sizes, or the hairs on the inner surfaces of the hind basitarsi are red to yellow. Go to 43

43. (42) The galeae are dull above due to dense reticular shagreening and the hairs on the inner surfaces of the hind basitarsi are often red to yellow, and on rare occasions, dark reddish brown. The mesoscutum usually doesn’t have a dark patch of hairs, but if it does, then it’s smaller than that of the scutellum’s dark patch. The overall pale vestiture is ochraceous to yellow, prominently on the mesoscutum … subagilis

The galeae are shiny above without shagreening apart from areas nearing the tips, this being less than the apical half. If the galeae are dull due to shagreening, then either the hairs on the inner surfaces of the hind basitarsi are dark or the mesoscutum has a large dark patch of hairs that is minimally as large as the scutellar dark patch, or the overall pale vestiture is white. Go to 44

44. (43) The interband zone of the second tergum has white, appressed to subappressed pubescence with no darker spine-like hairs. The distal pale band of the second tergum isn’t medially interrupted and consists of rather lengthy, plumose, overlapping hairs. Go to 45

The interband zone of the second tergum has dark brown, appressed to subappressed, spine-like hairs. If there are no dark brown, appressed to subappressed, spine-like hairs, then the distal pale band of the second tergum medially consists of rather short, non-overlapping (apart from the basal area of the band), scalelike hairs that usually become narrowly medially interrupted … lutulentus

45. (44) The galeae are dull above due to shagreening, minimally in the apical one-third to one-half and often more. The hairs on the mesoscutum are usually dark posteromedially … utahensis

The galeae are less dull above without shagreening apart from areas nearing the tips. The hairs on the mesoscutum aren’t dark … verbesinarum

46. (24) The second and third terga have very wide pubescent bands that diffuse over most of the tergum, prominently wide on the second tergum. The apical areas of the second and third terga are distinctly medially punctate, with punctures that are notably wider than the hairs that arise from them, posteriorly of the bands … tepidus

The second and third terga have narrower white bands that do not diffuse across most of the tergum. The apical areas of the second and third terga are not distinctly medially punctate posteriorly of the bands, or if there are punctures, then they are no wider than the base of the hairs that arise from them … communis

Melissodes

Photo credit: Frank Hogland

Scientific Classification

Kingdom

Phylum

Class

Order

Family

Tribe

Genus

Animalia

Arthropoda

Insecta

Hymenoptera

Apidae

Eucerini

Melissodes

Melissodes are perhaps one of the most commonly found wild Apid bee genera in Oregon apart from Bombus and Ceratina (Best et al., 2021b; 2022b). In general, the genus is comprised of very setaceous, robust, and medium sized bees with the largest Oregonian Melissodes (M. glenwoodensis) in length, measuring 11-14 mm. in the female sex and 10-15 mm. in the male sex (Laberge, 1961; for reference, Apis melifera measures about 13.2 mm. on average; see DeGrandi-Hoffman et al., 2004). Males and females can be readily distinguished from one another by the increadibly long antennal length of the males and the scopae on the hind legs and robustness of the females. Melissodes are ground-nesting bees (Laberge, 1956a; Laberge, 1956b; Laberge, 1961; Michener, 2007) that are most active during the fall months, with peak activity occurring in August and July (see, in part, Fig. 12). This genus is widespread across the entirety of Oregon, but each species differs slightly in range (see species treatments). Overall, Melissodes as a genus are oligolects of Asteracae, and often nest near large quantities of these flowers (Parker et al., 1981), which seems reasonable as its been reported that some species home ranges are short, likely around 14-16 meters (Foy, 2025).

Field Markers

♂ Long antenna, often around more than two-thirds of their total body length and almost no malar margin. Very setaceous, and often having a yellow or pale colored clypeus (although there are exceptions; see M. tristis). The wings have 3 submarginal cells and the eyes tend to have a green color, though not always. The first flagellar segment is usually incredibly short compared to the rest of the flagellum (except in M. dagosus and sometimes M. rivalis) and the genal area is usually somewhat narrow laterally (though not always).

♀ Very setaceous and robust with large scopae on the hind legs and almost no malar margin. The wings have 3 submarginal cells and the clypeus is often not very protuberant (except for M. rivalis). The genal area is usually somewhat narrow laterally (not always) and the vertex is somewhat flat. The tegulae are narrowed anteriorly and the metasoma is often shorter and distally rounded (not wasp-like).

Similar Genera

Although they are a distinctive genus, Melissodes can superficially resemble other genera, prime examples of which are Eucera and Diadasia. Male Melissodes can reliably be distinguished from that of a male Diadasia by their long antennae and anteriorly narrowed tegulae (Fig. 7), although females can bear more of a resemblance due to their robustness and scopal hair location. Female Melissodes can be differentiated from that of female Diadasia due to the anteriorly narrowed tegulae and flatter vertex outlines when looking in facial view (Michener, 2007; Laberge, 1957; see Fig. 8). Distinguishing between Melissodes and Eucera can be a bit trickier as both genera reside in the same tribe (Eucerini) and therefore males cannot be separated by antennae length alone and females share similar features. The most common and most relioable way to separate both sexes of Melissodes from Eucera is with tegular shape, that being Melissodes tegulae are narrowed anteriorly and Eucera tegulae aren’t (Michener, 2007; Laberge, 1957; see Fig. 9). Males of Eucera often have entirely black antennae with no ventral red markings (not always the case, somes species have red colorations ventrally), highly distinct flagellar segmentation, and wider scapes in contrast to the often red ventral to dorsal antennal markings, less distinct flagellar segmentation, and narrower scapes of Melissodes (Fig. 10; male Melissodes microstictus have entirely black antennae as well, except for a ventral pale macula, but the flagellar segments are less distinct, the genal area is smaller, and the clypeus is less protuberant than that of a male Eucera). Both sexes of Eucera also tend to have larger genal area to eye ratios (not always; Fig. 11), and earlier phenological activity than that of Melissodes (Fig. 12).

Fig. 7. A comparison of the males of Melissodes and Diadasia showing the differances in antennal length and structure of the tegulae (Melissodes on the left, Diadasia on the right). Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 8. A comparison of the females of Melissodes and Diadasia showing the differances in vertex and tegulae structure (Melissodes on the left, Diadasia on the right). Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 9. A comparison of both sexes of Melissodes and Eucera showing the differance in tegulae structure (females above, males blow; Melissodes on the left, Eucera on the right). Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 10. A comparison of males of Melissodes and Eucera showing the differance in antennal coloration and structure (Melissodes on the left, Eucera on the right). Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 11. A comparison of both sexes of Melissodes and Eucera showing the differance in eye to genal area ratios (females above, males blow; Melissodes on the left, Eucera on the right). Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 12. A graph representing the phenology of the genus Melissodes and Eucera in Oregon (blue represents Melissodes and red represents Eucera). The x value is the month, and the y value is the percentage of documented observations occurring in that month. Note the peak activity of Melissodes occurs in fall, much later than Eucera. Melissodes data compiled from (Ikerd, 2019; Johnson, 2020; Best et al., 2021a; Graham et al., 2021; Best et al., 2022a; Ikerd & Engler, 2023; Texas A&M University Insect Collection, 2023; Droege & Maffei, 2025; Gibbs, 2025; Bentley & Osborn, 2026; Best, 2026; Colorado State University, C.P. Gillette Museum of Arthropod Diversity, 2026; Frost Entomological Museum, 2026; Grinter et al., 2026; Gross & Oboyski, 2026; Illinois Natural History Survey, 2026; Johnson, 2026; Motz, 2026; MT James Entomological Collection, Washington State University, 2026; The International Barcode of Life Consortium, 2026) and Eucera data compiled from (Ikerd, 2019; Best et al., 2021a; Graham et al., 2021; Best et al., 2022a; Ikerd & Engler, 2023; Texas A&M University Insect Collection, 2023; VanDyk et al., 2023; Gibbs, 2025; Grant et al., 2025; Bentley & Osborn, 2026; Best, 2026; Illinois Natural History Survey, 2026; Johnson, 2026; Orrell & Informatics, 2026a; San Diego Natural History Museum, 2026; The International Barcode of Life Consortium, 2026; University of Minnesota Insect Collection, 2026). Data licensed under CC BY 4.0, CC BY-NC 4.0, and CC0 1.0 (see "Dataset Licenses").

Fig. 13. A graph showing the number of Melissodes documentation per species representing the most to least common. The x value is the species, and the y value is the number of documented observations. Data derived from ((Ikerd, 2019; Johnson, 2020; Best et al., 2021a; Graham et al., 2021; Best et al., 2022a; Ikerd & Engler, 2023; Texas A&M University Insect Collection, 2023; Droege & Maffei, 2025; Gibbs, 2025; Bentley & Osborn, 2026; Best, 2026; Colorado State University, C.P. Gillette Museum of Arthropod Diversity, 2026; Frost Entomological Museum, 2026; Grinter et al., 2026; Gross & Oboyski, 2026; Illinois Natural History Survey, 2026; Johnson, 2026; Motz, 2026; MT James Entomological Collection, Washington State University, 2026; The International Barcode of Life Consortium, 2026). Data licensed under CC BY 4.0, CC BY-NC 4.0, and CC0 1.0 (see "Dataset Licenses").

Melissodes agilis

Photo credit: Jane Abel (CC-BY-NC 4.0)