Melissodes bimatris

Photo credit: Lisa H. Robinson

Scientific Classification

Kingdom

Phylum

Class

Order

Family

Tribe

Genus

Subgenus

Species

Animalia

Arthropoda

Insecta

Hymenoptera

Apidae

Eucerini

Melissodes

Eumelissodes

M. bimatris

Binomial Name

Melissodes bimatris

Melissodes bimatris Laberge, the mothered long-horned bee, is a somewhat common North American species of Melissodes that tends to occupy the western portions of the United States (Laberge, 1961; Fig. 13). Like all Melissodes, male M. bimatris have long antennae, and the females have short antennae in comparison (see "Genus" page for more information). This species resides in the subgenus Eumelissodes Laberge and females are highly variable, but in a very distinctive manner. Unlike most variable species of Melissodes, M. bimatris females have two distinct forms (dark and light) rather than a range of intergrades as in M. druriellus or M. rivalis, apart from a few specific characteristics. Both sexes of M. bimatris can resemble other species in M. (Eumelissodes) Laberge, but dark females are easily distinguished from all other species by their overall black to dark brown vestiture with bright ochraceous to yellowish dorsal thoracic highlights coupled with pale fluvo-ochraceous scopae (Laberge, 1961). Lighter females, however, are fairly more challenging to identify, bearing high resemblance to those of M. ochraeus and M. semilupinus (although more so the former than latter). Males can be distinguished from most other M. (Eumelissodes) Laberge by their shiny galeae, entirely black mandibles, entirely yellow clypeaus, fairly long first flagellar segment (in comparison to those of M. agilis or M. trinodis), hyaline tergal rims, the first flagellar segment’s maximum length being more than one-third of the third segment’s minimum length, and the noticeably dense apical band of appressed to subappressed hairs that obscure the apical margin across the entire tergum (see “Description and Identification” for more information on both sexes) (Laberge, 1961). M. bimatris is seemingly an oligolege of the family Asteraceae with a strong preference towards the genus Chrysothamnus (Laberge, 1961). However, collections have shown that M. bimatris seems to significantly prefer Ericameria (as well as Chrysothamnus) above all other floral documentations (Carril et al., 2023; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; Kenneth S. Norris Center for Natural History, 2026; MT James Entomological Collection, Washington State University, 2026). Given how similar the two Asteraceae genera are, this may instead reflect recent floral taxonomic revisions (i.e. many Chrysothamnus being reclassified as Ericameria) rather than a true new specialized floral-host relationship (see “Flower records” for more information).

Description and Identification

Based on Laberge's (1960) description, Melissodes bimatris are medium sized setacouse bees. Females range from 11 to 15 millimeters in length and 4.0 to 5.5 millimeters in width (width measured at the widest portion of the metasoma). Males are a bit smaller, being about 10 to 14 millimeters in length and 3 to 4 millimeters in width (width measured at the widest portion of the metasoma). The female's first flagellar segment is on average 1.96 times the size of the second flagellar segment (standard deviation 0.022). The males are the opposite where the second flagellar segment is on average 4.68 times the size of the first flagellar segment (standard deviation 0.089). Female wing length is 4.10 millimeters on average (standard deviation 0.150 millimeters), and male wing length is 3.88 millimeters on average (standard deviation 0.167 millimeters). Females have an average of 14.75 hamuli (standard deviation 0.298), while males have an average of 13.30 (standard deviation 0.219).

Female

According to Laberge (1961), the description of female M. bimatris is as follows. The integument is black, differing at the eyes, which are gray (although not from Laberge, 1961, a dark blue eye color is common as well); the wing membranes, which are colorless to finally milky hyaline; the wing veins, which are black to dark brownish red; the underside of flagellar segments 3-10, which are somtimes rufescent, but often entierly black to dark brown; the apical one-half of the mandibles, which are rufescent; the tibial spurs, which are pale yellow to colorless hyaline; the distitarsi, which are rufescent; and the apical area of the first tergum, which has a narrow hyaline margin. The clypeus is rather flat, and usually has a medial longitudinal carina. The oculoclypeal distance is less than or equal to half the first flagellar segment’s diameter. The clypeus is somewhat dull due to reticular coarse shagreening (including the bottom of the punctures) and has shallow, round, coarse punctures that are mostly separated by less than one-half of a puncture diameter. The flattened lateral areas of the vertex are shiny and have irregularly sized small punctures that are mostly separated by one-half to two puncture diameters. The width of the second flagellar segments is moderately wider apically than its median length ventrally, or the length and the width are approximatly the same; the length is never greater than the apical width (Fig. 1). The four maxillary palpal segments decrease in length from basal to apical in a ratio of about 3.0:2.7:2.3:1.0. The galeae are shiny with no shagreening dorsally excluding some faint delicate shagreening in less than, or equal to, the apical half. The mesoscutum is shiny and sparsely or not at all shagreened (Fig. 2) and has deep large punctures that vary in diameter and are mostly separated by one-half to one puncture diameter. The large posteromedian area of the mesoscutum isn’t shagreened, has punctures that tend to be slightly larger and sparser than the rest of the mesoscutum, and these punctures are separated by at least one and usually by more than two puncture diameters. Punctures of the scutellum are similar to the punctures on the mesoscutum, but they are slightly more crowded. The metanotum is dulled by very fine reticular shagreening, and has punctures that are half the diameter of the punctures on the scutellum. These punctures are mostly separated by one-half to one puncture diameter. The propodeum’s dorsal surface is reticulorugose and is especially coarse basally, and the posterior surface has coarse punctures except for the upper triangle. The lateral surfaces of the propodeum are similar to the posterior surface but the punctures are more crowded and the surfaces are dulled by dense regular tessellation. The mesepisternum’s lateral surface has punctures that are large, shallow, and separated mostly by half a puncture diameter or less. The surface of the mesepisternum is shiny with weak, incredibly sparse, delicate shagreening.

The first tergum’s basal three-fifths or slightly less is dulled by fine tessellation and the basal two-thirds or more is medially punctate (Fig. 3). These punctures are round, shallow, and separated mostly by one-half to one and one-half puncture diameters; punctures can extend to the apex at extreme sides. The apical area of the first tergum is impunctate with a shiny surface that is extremely finely reticulotransversely shagreened. The second tergum’s basal zone is shiny but has fine reticular shagreening and tiny round punctures that are separated by one to half a puncture diameter. The interband zone of the second tergum is dulled by reticulotransverse shagreening and has small irregular punctures that are separated by one to three puncture diameters; these punctures are sparser medially than in the lateral raised areas. The apical area of the second tergum is moderately shiny, but dulled with fine reticulotransverse shagreening and has minute punctures that are no wider than the base of the hairs that arise from them located at minimum near the distal bands and sometimes more. Each of these punctures are separated by two to four puncture diameters. The third tergum is similar to that of the second, but the punctures of the interband zone are relatively more distinct and abundant. The fourth tergum is similar to that of the third, but the apical area is usually impunctate, or if punctate, then it has minute punctures that are no wider than the base of the hairs that arise from them that are separated by two to four puncture diameters. The pygidial plate is broadly V-shaped with a rounded apex and is about two-tenths longer medially than the width of its base.

Two setal variations of M. bimatris are present across its range (dark and light) in a seemingly unpredictable and somewhat homogenous way, suggestive of no subspecific separation (Fig. 4). Interestingly, M. bimatris seems to exhibit forms of intergradation in multiple characteristics such as the head hairs, metasomal hairs, and thoracic hairs. However, intergrades seem somewhat less common in comparison to the two extremes, a strange scenario given the presence and intermixture of both extremes across similar areas. Furthermore, given the binary nature of the intergrade characteristics (no real “graying” seems to occur, rather a few pale characteristics may be found on an entirely dark individual), it’s fairly reasonable to assume that some sort of codominance is occurring within their setal color alleles; this seems almost contradictory to the findings above. More genetic research is needed to determine the full spectrum M. bimatris’ dimorphism. The palest M. bimatris individuals have entirely pale ochraceous head hairs with no distinctive vertex, clypeal, or mandibular darkening. The thoracic hairs are mostly white to very pale ochraceous in the lateral as well as the posterior areas, becoming fairly rufescent to pale ochraceous in the dorsal areas; no dark patch present (Fig. 5). The first tergum’s basal area has long, pale ochraceous hairs that reach the apical margin at extreme lateral areas but not medially. However, the apical portion of the basal area bears long fairly appressed hairs that reach and often extend past the apical margin (often medially worn). The apical area of the first tergum is glabrous. The second tergum’s pale ochraceous basal pubescence is distinctly separated from the distal band across most of the tergum, but the two laterally connect. The interband zone of the second tergum has rather simple, erect ochraceous hairs; distinctly not bearing suberect to appressed plumose hairs as in M. ochraeus. The distal pale ochraceous pubescent band of the second tergum is two times the length of the apical glabrous area laterally, and medially, the band is narrowed and notched measuring only half the length of the apical glabrous area. The third tergum is similar to that of the second, except the basal tomentum is dark brown and the distal pale band is largely separated from the apical margin. The apical area of the third tergum is glabrous, apart from a few suberect hairs that are sometimes present near the distal most area of the pubescent band, and approximately as wide at the distal pale band medially (Fig. 6). The fourth tergum is similar to that of the third, but the distal pale band reaches the apex across the entire tergum and is distinctly medially narrowed with the basal dark pubescence often being wider than the band. The fifth and sixth terga are entirely covered in brown hairs and often have no (or very few) white lateral tufts. The hairs on legs are mostly white to pale ochraceous except for the fore tarsi, which are dark reddish brown to brown; the outer apical area of the fore tibiae and middle tibiae, which are dark reddish brown to brown; the basitibial plates and the surrounding areas, which are dark reddish brown to brown; the inner surfaces of the hind basitarsi, which are brownish red to sometimes entirely red; and the scopal hairs, which are often pale yellow, sometimes pale ochraceous, and incredibly long. The darkest M. bimatris individuals have entirely black to dark brown head hairs (Fig. 7). The thoracic hairs are completely black to dark brown except as follows: the dorsal thoracic areas apart from the tegulae, anterior mesoscutal surface, and propodeum, which are pale rufescent to pale ochraceous with no dark thoracic patches (Fig. 7). The vestiture of the metasoma is completely black to dark brown and the apical portion of the basal area bears long fairly appressed hairs that reach and often extend past the apical margin (often medially worn; Fig. 8). The leg hairs are black to dark brown, differing at the scopae, which are ochraceous yellow apart from the hairs at the apical basitarsal areas and around the basitibial plate (presented as “pygidial plate” in Laberge, 1961, however, this seems to be a possible typo as the pygidial plate has no relation to leg vestiture and the basitibial plate is a known morphological characteristic that bears darkened hairs on other species of Melissodes); the inner surfaces of the hind tibiae, which are also ochraceous to yellow; the inner surfaces of the hind basitarsi, which are black to dark brown (distinctly contrasting with scopae); and the hind femora, which are somewhat paler on the dorsal areas (Fig. 9).

M. bimatris ranges in setal color between these two dark and pale descriptions. As this species progressively lightens from the dark extreme to the pale extreme, pale tergal, thoracic, and facial hairs start to appear. To describe these variations, 10 characteristics each having two (and three on the thoracic hair characteristic; see note) different levels of melanism derived from descriptions of Laberge (1961) are listed below rather than writing singular descriptions for each theoretical variety (1,536 or 2^9*3 possible morphs). These are listed in the table below (table 1). Traits of differing levels of melanism are meant to be applied to, and override portions of, the pale description above. Note that each value per character (light, intermediate, or dark) is treated as being independent from one another (although, many are likely highly correlated). Therefore, a female M. bimatris may have all of its head hairs dark (darkest choice for the first character), and also have a pale band across the fourth tergum (palest choice for the sixth character); although, this combination has never been documented. Many characteristics have only two variations, one for the darkest and one for the lightest extreme, somewhat indicative of codominance rather than an incomplete dominance.

Note: the thoracic vestiture is the only included character that has an intermediate variation. However, this character isn’t a darkish gray color as it would be if M. bimatris expressed incomplete dominance, but rather an even mix of both extremes, supporting the original hypothesis.

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

Character	Light	Intermediate	Dark
Labral and mandibular hairs	Only pale hairs present.		Only dark hairs present.
Clypeal hairs	Only pale hairs present.		Only dark hairs present.
Vertex hairs	Mostly pale hairs present.		the majority of the hairs are pale, often extending downward in the genal areas creating an entirely dark head.
Thoracic hairs	The thoracic hairs are mostly white to very pale ochraceous in the lateral as well as the posterior areas, becoming fairly rufescent to pale ochraceous in the dorsal areas.	The thoracic hairs are mostly white to very pale ochraceous in the upper lateral areas (dark in the lower lateral areas), becoming fairly rufescent to pale ochraceous in the dorsal areas.	The thoracic hairs are completely black to dark brown except as follows: the dorsal thoracic areas apart from the tegulae, anterior mesoscutal surface, and propodeum, which are pale rufescent to pale ochraceous (no dark thoracic patches).
Hairs on the base of the second tergum	Pale hairs present and abundant.		Mostly to entirely black to dark brown.
Hairs on the base of the first tergum	Pale hairs present and abundant.		the majority to all of the hairs are black to dark brown.
Distal pale band of the second tergum	Pale hairs are distinctly present to all of the hairs are pale.		the majority to all of the hairs are black to dark brown.
The distal band of the third tergum	Pale hairs are distinctly present to all of the hairs are pale.		the majority to all of the hairs are black to dark brown.
Hairs on the fourth tergum	The entire band is distinctly pale, only a few, if any, dark hairs are present (likely these hairs are basal to the band, not truly constituting as the band).		The entire band is black..
The distal band of the third tergum	The majority of the leg hairs are distinctly pale, not all of a similar color, but pale non-the-less.		The leg hairs are almost entirely black to dark brown with bright ochraceous to fluvo-ochraceous scopae on the hind legs.

It’s still unknown to what degree M. bimatris females truly vary. From the specimens available at his time of publication, Laberge (1961) listed 173 females, 169 of which were the two extremes (96 dark and 73 light), 14 of which were intermediate-dark, 7 of which were intermediate, and 9 of which were intermediate-pale. 97.7% of Laberge’s (1961) female M. bimatris material were of the two extremes, and given the extensive sampling across their ranges, this seems to reflect a natural phenomena. This is strange as very few intergrades are found, possibly indicative of a cryptic species and/or a supergene. A genetic study will need to occur to determine the full breadth of phenotypic variation in M. bimatris females.

Fig. 1. A labeled diagram showing the length of the second flagellar segment of females of M. bimatris (left) in comparison to those of M. menuachus, demonstrating the apical width and ventral lengh are approximatly equal in M. bimatris. The red lines are indicative of the ventral length and the white lines indicate the apical width. An enlarged width/length comparison (10x) is given below each female. Photo credit: Christopher Wilson (All Rights Reserved).

Fig. 2. A comparison of the mesoscutal sculpturing of a femal M. bimatris (left), and a female M. trinodis (right), illustrating the shiny nature of the mesoscutum of the female M. bimatris. Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 3. A labeled diagram showing the ratio of the basal punctate area to the impunctate apical area of the first tergum of a female M. bimatris. Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 7. A labeled diagram showing the head and thoracic vestiture of a dark female M. bimatris. Photo credit: Lori Weidenhammer (CC-BY-NC).

Fig. 8. A labeled diagram showing the metasomal vestiture of a dark female M. bimatris. Photo credit: Lori Weidenhammer (CC-BY-NC).

Fig. 9. A labeled diagram showing the leg vestiture of a dark female M. bimatris. Photo credits: Lori Weidenhammer (CC-BY-NC).

Male

According to Laberge (1961), the description of male M. bimatris is as follows: the integument is black, differing at the eyes, which are green to gray; the clypeus, which is yellow except for the usually piceous apical margin; the labrum, which is usually completely black, although sometimes there’s a small pale maculation positioned mediobasally (Fig. 10); the wing membranes, which are colorless hyaline; the wing veins, which are black to dark reddish brown; flagellar segments 2-10 which are red to yellow on the underside and dark red to brown on top (first segment completely dark brown); the distitarsi, which are rufescent; the tegulae, which are piceous; and the apices of the terga, which are colorless to yellow hyaline. The mandibular bases are completely dark, bearing no yellow macula (Fig. 10). The clypeus protrudes beyond the eye by about half the width of an eye in profile view. The first flagellar segment’s minimum length is about two-thirds of its maximum length, and about one-fifth or somewhat less than the maximum length of the second segment (Fig. 11). The penultimate segment is about three times as long (maximum) as it is wide (minimum). Flagellar segments 8-10 or 7-10 are somewhat crenulate, similar to that of the male M. semilupinus. All flagellar segments do not have longitudinal lateral depressions. The four maxillary palpal segments decrease in length from basal to apical in a ratio of about 4.0:3.5:3.5:1.0. The remainder of the sculptural characteristics are similar to that of the female except as follows: the basal punctures of the first tergum extend past the basal five-sixths medially; the punctures of the second and third terga are often more crowded and faintly coarser.

The 7th sternum’s median plate is subtriangular, slightly larger than the lateral plate, and the apical margin is medially inclined. The lateral plate of the 7th sternum is also subtriangular. The 7th sternum’s median plate also has abundant minute ventral hairs that are coarse and long basally, a few hairs that become curled and inwardly directed from the dorsal areas of the basal areas inner angle, and sparser and more delicate mediobasal hairs; these hairs are sparser and more slender than those of M. dentiventris. The membranous area between the plates is narrow and almost half the size of the lateral plate. The apicomedial margin located between the median plates has strongly curved carinae on each side. The 8th sternum is broad near the apex, has several to many hairs on the apical margin, distinctly emarginate apicomedially, and the ventral tubercle usually isn’t apically bidentate, but is cariniform. The ventral tubercle does not reach the apical margin of the 8th sternum. The Gonostylus is slender, tapers apically, has short, blunt, sparse, hairs basally on the ventral surface, short, stout, bifid or trifid hairs apically, and isn’t distinctly capitate. The length of the gonostylus is approximately half the length of the gonocoxite. The spatha is about three times as wide as it is long. At least half of the spicules of the upper inner surface of the gonocoxite are short and blunt, and the rest are hairlike. The ventral surface of the gonocoxite below the gonostylus doesn’t bear any stout, blunt, short spicules apically (differing from that of M. menuachus). The penis valve has a prominent dorsolateral lamella; the basal end of the lamella ends in an inflected tooth near the spatha.

Unlike their female counterparts, males of M. bimatris do not distinctly range in vestiture, the description of which follows. The hairs on both the head and the thorax are white to pale ochraceous, but on the vertex of the head and the dorsal area of the thorax, the hairs usually become a bit darker. The first tergum has long basal white to ochraceous hairs and long appressed to subappressed apical pale hairs that reach and obscure the apical margin across the entire tergum as long as they aren’t worn off (Fig. 12). The second tergum has white basal pubescence and pale erect, bristle-like hairs on the interband zone. The distal pubescent band of the second tergum is not interrupted medially and often narrower than the apical area. The apical area of the second tergum has many suberect pale hairs. Terga 3-5 are similar to that of the second tergum except for the interband zones, which in addition to the bristle-like hairs there are also delicate, sparse, white, appressed pubescence; interband zone hairs suberect instead of erect. Also, the distal bands of terga 3-5 become closer to the apical margin with each tergum. The sixth and seventh terga are covered in yellowish to white pubescence. The sternal hairs are medially reddish to pale ochraceous, and laterally white. The legs have white to ochraceous hairs excluding the yellow inner surfaces of the tarsi. Two males have been found to have pale rufescent to yellow-ochre and brownish red pubescence basally on terga 3-5.

Fig. 11. A comparative diagram showing the ratio of flagellar lengths of a male M. bimatris. The yellow line is indicative of the longer side (maximum length) of F2, the red line indicates the longer side of F1, and the white line represents the shorter side of F1. These are as described above, but the short side of F1 is slightly longer than two thirds of the maximum length of the same segment (this is still representative of a regular M. bimatris). An enlarged width/length comparison (2.5x) is given below. Photo credits: Christopher Wilson (All Rights Reserved).

Fig. 12. A labeled diagram showing the dense appressed apical band of hairs on the first tergum that obscures the apical margin across the entier tergum of a male M. bimatris. Photo credits: Christopher Wilson (All Rights Reserved).

Location and Habitat

Melissodes bimatris is a somewhat uncommon, although not elusive, species that seems to occur across the majority of the pacific coast and somewhat inland of it (Laberge, 1961). In his revision, Laberge (1961) documented the range of M. bimatris to include the following states and provinces: California, Nevada, Utah, Oregon, Washington, Idaho, Arizona, and New Mexico; noting that a male collected in Colorado has been identified as M. bimatris, although the specimen is in fairly poor condition and therefore cannot be determined with 100% certainty. A similar distribution can be seen today, however, this species has been collected in an additional 4 states; 3 somewhat westward of its original proposed range and 1 distinctly western. Currently, M. bimatris has been found in the listed states above with the addition of Montana (Ikerd, 2019), Wyoming (Illinois Natural History Survey, 2026), Colorado (Ikerd, 2019, with a number of definitive specimens), and Kansas (Bentley & Osborn, 2026; see Fig. 2). Although it’s unknown what habitats in which M. bimatris resides, its host-plants, Ericameria and Chrysothamnus (see “Flower records for more detail), are known to inhabit dry regions (Scheinost et al., 2010), “desert to semi-desert habitats" (Tirmenstein, 1999; Tilley et al., 2012), and tend to be found in regions with “dry, well-drained medium to coarse-textured soils” as noted by Tirmenstein (1999). Specifically, the species Chrysothamnus viscidiflorus has been documented in a range that can be drawn from Texas, Arizona, and North Dakota, west to California, and north towards British Columbia, a very similar distribution to that of M. bimatris. Given this, it’s reasonable to assume that M. bimatris occupies similar habitats to its preferred genera, likely being found in large aggregations of these floral taxa. Currently, the only phenological activity published for M. bimatris states that this species has been documented to be active throughout the months of June to November, the latest specimen being collected on the 8th of the latter month, with peak activity likely occurring in September (Laberge, 1961). Newer data seem to indicate a very similar pattern to that described in the past, the only distinct difference being that M. bimatris has been collected as early as May; although, these collections are few (Fig. 14).

Fig. 13. Map showing an estimation for the known distribution for M. (Eumelissodes) bimatris. Each point represents 1 or more occurrences; occurrences that don't have coordinates are not included. Data derived from (Ikerd, 2019; Johnson, 2020; Carril et al., 2023; Texas A&M University Insect Collection, 2023; Bentley & Osborn, 2026; Brigham Young University, Arthropod Collection, 2026; Gibbs, 2026; Grinter et al., 2026; Gross & Oboyski, 2026; Illinois Natural History Survey, 2026; Kenneth S. Norris Center for Natural History, 2026; Mertz et al., 2026; MT James Entomological Collection, Washington State University, 2026; Museum of Southwestern Biology, 2026; Orrell & Informatics, 2026; The International Barcode of Life Consortium, 2026; University of Arizona Insect Collection, 2026). Data licensed under CC BY 4.0, CC BY-NC 4.0, and CC0 1.0.

Fig. 14. A figure showing the phenological activity of M. bimatris. The x value is the month, and the y value is the number of documented observations. Data derived from (Ikerd, 2019; Johnson, 2020; Carril et al., 2023; Texas A&M University Insect Collection, 2023; Bentley & Osborn, 2026; Brigham Young University, Arthropod Collection, 2026; Gibbs, 2026; Grinter et al., 2026; Gross & Oboyski, 2026; Illinois Natural History Survey, 2026; Kenneth S. Norris Center for Natural History, 2026; Mertz et al., 2026; MT James Entomological Collection, Washington State University, 2026; Museum of Southwestern Biology, 2026; Orrell & Informatics, 2026; The International Barcode of Life Consortium, 2026; University of Arizona Insect Collection, 2026). Data licensed under CC BY 4.0, CC BY-NC 4.0, and CC0 1.0.

Bionomics

No publications have currently concerned themselves with the studies of nesting behaviors or bionomics of M. bimatris. From the data available, M. bimatris seems to occupy elevations ranging between 51m (University of Arizona Insect Collection, 2026; GBIF record 4070489082) and 2,283m (Carril et al., 2023; GBIF record 3421504713), but one observation was documented in Whitney Portal, California (Illinois Natural History Survey, 2026; GBIF record 3801936780), which, in accordance to the National Geodetic Survey, is approximately 2,552.5m. However, the record doesn’t contain any reports of elevation, and the supposed elevation may therefore be wrong. For this reason, the elevation range of M. bimatris will herein be documented as 51-2,283 meters. Taking into account the codependency of M. bimatris and their preferred floral hosts, the location of Ericameria and Chrysothamnus may dictate the soil in which M. bimatris nests. As it has been documented that one of the two flower genera (Chrysothamnus) often occupy areas with “dry, well-drained medium to coarse-textured soils” (Tirmenstein, 1999), and that the flight range of other Melissodes species (M. agilis) predicted to be 14-16m (Foy, 2025), it’s fairly reasonable to assume that M. bimatris nests near their floral hosts and in turn nests within the Ericameria and Chrysothamnus’ preferred soil type. More research is needed to fully understand the ecology of M. bimatris.

Flower records

At the time of his publication, Laberge’s (1961) M. bimatris material consisted of 144 specimens bearing floral data. From this, it was determined that M. bimatris is oligolectic towards Asteraceae and has a strong preference, and a possible specialization, to the genus Chrysothamnus due to the overwhelming number of collections from this taxon (121 M. bimatris collected atop Chrysothamnus; 84.02%). The remainder of the records consisted of miscellaneous genera and species with no significant values (Laberge, 1961). The records given in full by Laberge (1961) consisted of 23 floral taxa, 10 of which were of the Chrysothamnus (at least historically classified as such). These will be listed in full below. Unlike many of his other species treatments, Laberge (1961) opted to omit a table representing the frequencies of a specific floral taxon within his database, likely due to the substantial Chrysothamnus preference observed. In this treatment, a diagrammatic representation of M. bimatris’ floral frequency will be presented, the data derived from 5 datasets and 435 floral records. To preface this, a list of all current records will be listed with updated taxonomy. All flower records included in this list are from reports in the literature or datasets. Each flower has a parenthesized reference listed after it, corresponding to the literary work or dataset in which it was recorded. Artemisia (Laberge, 1961; presented as “Artemesia sp.” a likely misspelling), Aster sp. (Laberge, 1961), Centromadia pungens (Laberge, 1961), Chrysothamnus sp. (Laberge, 1961), Chrysothamnus depressus (Carril et al., 2023; GBIF record 3421470407), Chrysothamnus greenei (Carril et al., 2023; GBIF record 3421476005), Chrysothamnus viscidiflorus (Laberge, 1961), Cleome sp. (Bentley & Osborn, 2026; GBIF record 1092783623), Dieteria canescens (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141264369), Ericameria arborescens (Kenneth S. Norris Center for Natural History, 2026; GBIF record 2562700965), Ericameria nauseosa (Laberge, 1961; old synonym), Ericameria nauseosa var. hololeuca (Laberge, 1961; old synonym), Ericameria nauseosa var. mohavensis (Laberge, 1961; old synonym), Ericameria nauseosa var. oreophila (Laberge, 1961; old synonym), Ericameria nauseosa var. speciosa (Laberge, 1961; old synonym), Ericameria palmeri (Laberge, 1961), Ericameria parryi (Laberge, 1961; old synonym), Eriogonum sp. (Laberge, 1961), Eriogonum corymbosum (Carril et al., 2023; GBIF record 3421474744), Eriogonum niveum (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141245332), Euthamia occidentalis (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141245528), Frangula californica subsp. californica (Laberge, 1961; old synonym), Grindelia sp. (Bentley & Osborn, 2026; GBIF record 657745275), Grindelia squarrosa (Carril et al., 2023; GBIF record 3421471768), Gutierrezia californica (Laberge, 1961), Gutierrezia microcephala (Laberge, 1961; old synonym), Gutierrezia sarothrae (Laberge, 1961), Helianthus sp. (Laberge, 1961), Helianthus annuus (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141248520), Helianthus petiolaris (Carril et al., 2023; GBIF record 3421462589), Heliomeris multiflora (Carril et al., 2023; old synonym; GBIF record 3421470197), Heterotheca villosa (Carril et al., 2023; GBIF record 3421529497), Hymenopappus filifolius (Carril et al., 2023; GBIF record 3421453033), Isocoma sp. (Bentley & Osborn, 2026; GBIF record 1899931729), Isocoma acradenia (Laberge, 1961), Linum subteres (Carril et al., 2023; GBIF record 3421498262), Lorandersonia linifolia (Carril et al., 2023; old synonym; GBIF record 3421490589), Melilotus albus (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141240281), Monardella odoratissima (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141240382), Nepeta cataria (MT James Entomological Collection, Washington State University, 2026; GBIF record 5141245871), Senecio sp. (Laberge, 1961), Senecio flaccidus (Carril et al., 2023; GBIF record 3421437355), Senecio spartioides (Carril et al., 2023; GBIF record 3421530397), Stephanomeria (Carril et al., 2023; GBIF record 3421444041), Stephanomeria exigua (Carril et al., 2023; GBIF record 3421464009), Stephanomeria tenuifolia (Carril et al., 2023; GBIF record 3421496314), Thelypodium integrifolium (Carril et al., 2023; GBIF record 3421472728).

Fig. 15. A graph showing the raw current-day known floral data of M. (Eumelissodes) bimatris from 5 datasets. Data derived from (Carril et al., 2023; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; Kenneth S. Norris Center for Natural History, 2026; MT James Entomological Collection, Washington State University, 2026). Data licensed under CC BY-NC 4.0 and CC BY 4.0.

Fig. 16. A graph showing unique events of current-day known floral data of M. (Eumelissodes) bimatris from 5 datasets. Each floral taxon is filtered to only include records with unique latitudes, longitudes or dates in an attempt to prevent single-site sampling bias. Data derived from (Carril et al., 2023; Bentley & Osborn, 2026; Illinois Natural History Survey, 2026; Kenneth S. Norris Center for Natural History, 2026; MT James Entomological Collection, Washington State University, 2026). Data licensed under CC BY-NC 4.0 and CC BY 4.0.

From what is apparent in the graphs above, M. bimatris seems to be an Asteraceae oligolege with a distinct preference of the genera Ericameria and Chrysothamnus (Figs. 15 & 16). The latter of these taxa was originally presumed to be the sole genus on which M. bimatris specialized (Laberge, 1961), but these newer data seem to suggest otherwise. However, Ericameria and Chrysothamnus are both incredibly closely related, the former now containing many taxa that were originally believed to be Chrysothamnus (Nesom & Baird, 1993) at the time of Laberge’s (1961) publication. The combination of these floral taxa account for approximately 70.43% of all records, and of the total families on which M. bimatris was collected, Asteraceae accounts for approximately 95.35%; the remaining six families only having 1-2 records per family.

Taxonomy and Phylogeny

Unlike many other Melissodes, M. bimatris has no significant taxonomic history. This species was first added to the genus by Laberge (1961) and has had no since revisions. However, Laberge (1961) did note that prior to his publication, he had separated both extremes of the females into separate species (a reasonable assumption). While he recognized both morphs as a single taxon (further validated by the presence of intergrades as described above), Laberge (1961) also clarifies that a possibility of cryptic taxa and/or two separate species still exists. Due to the lack of a latin suffix appended to the root, M. bimatris did not undergo a taxonomic epithet reclassification with the addition of article 30.1.4.4 in the 1999 release of the International Commission on Zoological Nomenclature (ICZN).

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