Heather M. Hines

Kelpeltet, Myanmar

B.A. Biology/Anthropology, University of Iowa M.S. Entomology, University of Illinois Ph.D. Entomology, University of Illinois Heather Hines Department of Genetics Box 7614 North Carolina State University Raleigh, NC 27695-7614 Office: 3532 Thomas Hall email: heather_hines@ncsu.edu

As a Ph.D. student I focused primarily on the systematics and evolution of bumble bees (Hymenoptera: Apidae: Bombini). This culminated in the construction of a phylogeny of over 200 of the 250 bumble bee species of the world in collaboration with Dr. Sydney Cameron and Dr. Paul Williams (The Natural History Museum, London) (Cameron et al., 2007). This phylogeny provides good support and resolution across the bumble bees and resolves many of the conventional subgenera as monophyletic. The phylogeny served as a framework for reclassifying and simplifying the Bombus subgeneric system (Williams et al., 2008). We are using this phylogeny as a template for further research on Bombus character evolution, including studies on Bombus historical biogeography and divergence times (Hines, 2008) and the genetic control of color pattern. These projects and research I have engaged in on nest architecture in the neotropical bumble bee Bombus pullatus (Hines et al., 2007a), and on the evolution of sociality in Vespidae (Hines et al., 2007b), are described further under Ph.D. Research.

Extending upon my previous research on the phylogenetics and evolution of color pattern in the globally mimetic bumble bees, my current research focuses on the genes underlying the wing patterns of the neotropical Heliconius butterflies, a model system for the study of Müllerian mimicry and color pattern diversification. To infer gene networks responsible for differences among these morphs, I am utilizing gene expression data from butterfly races using microarrays and next generation sequencing. I am also studying Heliconius phylogeographic history and assessing the feasibility of using sequences from loci linked and unlinked to adaptive traits, such as color pattern, to better infer trait history. More information on these projects is provided under Postdoc Research.

Publications

1. The Heliconius Genome Consortium. 2012. Butterfly genome reveals promiscuous exchange of mimicry adaptations among species. Nature, http://dx.doi.org/10.1038/nature11041 2. Duennes, M. A., Lozier, J. D., Hines, H. M., and S. A. Cameron. 2012. Geographical patterns of genetic divergence in the widespread Mesoamerican bumble bee Bombus ephippiatus (Hymenoptera: Apidae). Molecular Phylogenetics and Evolution 64 (1): 219-231. 3. Miko, I., Friedrich, F., Yoder, M. J., Hines, H. M., Deitz, L. L., Bertone, M. A., Seltman, K. C., Wallace, M. S., and A. R. Deans. 2012. On dorsal prothoracic appendages in treehoppers (Hemiptera: Membracidae) and the nature of morphological evidence. PLoS ONE 7(1): e30137. doi:10.1371/journal.pone.0030137 4. Hines, H. M., Counterman, B. A., Papa, R., Albuquerque de Moura, P., Cardoso, M. Z., Linares, M., Mallet, J., Reed, R. D., Jiggins, C. D., Kronforst, M. R., and W. Owen McMillan. 2011. Wing patterning gene redefines the mimetic history of Heliconius butterflies. Proceedings of the National Academy of Sciences, USA 108: 19666-19671. 5. Reed, R. D., Papa, R., Martin, A., Hines, H. M., Counterman B. A., Pardo-Diaz, C., Jiggins, C. D., Chamberlain, N. L., Kronforst M. R., Chen, R., Halder, G., Nijhout, H. F., and W. O. McMillan. 2011. optix drives the repeated convergent evolution of butterfly wing pattern mimicry. Science 333: 1137-1141. 6. Hines, H. M. and S. A. Cameron. 2010. The phylogenetic position of the bumble bee inquiline Bombus inexspectatus and implications for the evolution of social parasitism. Insectes Sociaux 57: 379-383. 7. Counterman, B. A., Arajuo-Perez, F., Hines, H. M., Baxter, S. W., Morrison, C. M., Lindstrom, D. P., Papa, R., Ferguson, L., Joron, M., ffrench-Constant, R., Smith, C., Nielsen, D. M., Chen, R., Jiggins, C. D., Reed, R. D., Halder, G., Mallet, J., and W. O. McMillan. 2010. Genomic hotspots for adaptation: population genetics of Müllerian mimicry in Heliconius erato. PLoS Genetics 6 (2): e10000794. 8. Williams, P. H., Cameron, S. A., Hines, H. M., Cederberg, B., and P. Rasmont. 2008. A simplified subgeneric classification of the bumblebees (genus Bombus). Apidologie 39: 46-74. 9. Hines, H. M. 2008. Historical biogeography, divergence times, and diversification patterns of bumble bees (Hymenoptera: Apidae: Bombus). Systematic Biology 57: 58-75. 10. Cameron, S. A., Hines, H. M., and P. H. Williams. 2007. A comprehensive phylogeny of the bumble bees (Bombus). Biological Journal of the Linnean Society 91: 161-188. 11. Hines, H. M., Cameron, S. A., and A. R. Deans. 2007a. Nest architecture and foraging behavior in Bombus pullatus (Hymenoptera: Apidae), with comparisons to other tropical bumble bees. Journal of the Kansas Entomological Society 80: 1-15. 12. Hines, H. M., Hunt, J. H., O'Connor, T. K., Gillespie, J. J., and S. A. Cameron. 2007b. Multigene phylogeny reveals eusociality evolved twice in vespid wasps. Proceedings of the National Academy of Sciences, USA 104: 3295-3299. 13. Hines, H. M., Cameron, S. A., and P. H. Williams. 2006. Molecular phylogeny of the bumble bee subgenus Pyrobombus (Hymenoptera: Apidae: Bombus) with insights into gene utility for lower-level analysis. Invertebrate Systematics 20: 289-303. 14. Rasmont, P., Terzo, M., Aytekin, A. M., Hines, H., Urbanova, K., Cahlikova, L., and I. Valterova. 2005. Cephalic secretions of the bumblebee subgenus Sibiricobombus Vogt suggest Bombus niveatus Kriechbaumer and Bombus vorticosus Gerstaecker are conspecific (Hymenoptera, Apidae, Bombus). Apidologie 36: 571-584. 15. Hines, H. M., and S. D. Hendrix. 2005. Bumble bee (Hymenoptera: Apidae) diversity and abundance in tallgrass prairie patches: Effects of local and landscape floral resources. Environmental Entomology 34: 1477-1484. 16. Nelson, D. R., Hines, H., and B. Stay. 2004. Methyl-branched hydrocarbons, major components of the waxy material coating the embryos of the viviparous cockroach Diploptera punctata. Comparative Biochemistry and Physiology, Part B 138: 265-276.

Postdoctoral Research

The Genetics of Complex Wing Patterns in Heliconius Butterflies

As a NIH postdoctoral fellow at NCSU my primary research focuses on determining the genes underlying the exceptional wing color pattern variation in Heliconius erato utilizing genomic gene expression approaches. Heliconius erato and its comimic Heliconius melpomene converge onto a diversity of mimetic wing patterns across the neotropics. This results in numerous divergent and convergent natural replicates from which to examine genes underlying these adaptive phenotypes. Through a long history of genetic research, it has been determined that three major loci (D, Cr, and Sd) are responsible for the color pattern diversity of H. erato. While this research has narrowed the intervals containing the color pattern switch genes, we have yet to determine which genes in these intervals are regulating color pattern and how these genes interact to yield these complex and novel phenotypes. I am using gene expression microarrays that include probes that are tiled across the sequences at both the Cr and D loci to determine which genes in those intervals are differentially expressed in Heliconius races. I am also including EST and 454 sequences from the rest of the transcriptome on the arrays to determine genes that may be turned on downstream of these switch genes. These arrays involve sampling developing wing tissues across multiple stages and comparison between two separate hybrid zones with convergent phenotypes within Helionius erato (figure at right) . To supplement these results I am collecting Solexa/Illumina next generation sequence data from cDNA of Heliconius erato races. This research is being performed in collaboration with numerous researchers in the Heliconius community, but especially postdoctoral sponsors Owen McMillan, Bob Reed (UC Irvine), and with Riccardo Papa (U. of Puerto Rico), and Brian Counterman (Mississippi State) .

Ph.D. Research

Bombus Phylogenetics and Classification

I spent the first several years as a graduate student collecting data for a comprehensive species phylogeny of the bumble bees in collaboration with Drs. Sydney Cameron and Paul Williams. Williams (1998) recognizes ~250 species of bumble bees, of which we were able to obtain over 200 from several collecting trips (see Expeditions and the Cameron Lab webpage) and from numerous collaborators. For the phylogeny, I sequenced these taxa for 5 genes: mitochondrial 16S, elongation-factor 1-alpha (EF-1a), long wavelength rhodopsin (opsin), arginine kinase (ArgK), and phosphoenolpyruvate carboxykinase (PEPCK). Phylogenetic analysis of this data revealed a relatively well-resolved phylogeny using both Bayesian and parsimony analyses that supported the monophyly of most of the conventional subgenera with the notable exceptions of Fervidobombus, Tricornibombus, Dasybombus, and Separatobombus (Cameron et al., 2007). It has been argued (e.g., Menke and Carpenter, 1984) that the bumble bees have been oversplit into too many subgenera, largely because of their numerous mono or ditypic subgenera (50% of the subgenera) and the occurance of 38 subgenera for just 250 species. The new phylogenetic framework provides an opportunity for simplification of the traditional subgeneric system, both with regard to non-monophyletic subgenera and clusters of subgenera with few species. Most notable in this regard are several poorly speciose New World subgenera (e.g., Separatobombus, Fraternobombus) which were all resolved as monophyletic in the phylogeny and therefore can be defined as a more broad subgenus Cullumanobombus. In August 2006, I attended a meeting in Sweden with a group of bumble bee systematists to discuss this reclassification. From this discussion, a new subgeneric system has been devised (Williams et al., 2008). Comprehensive bumble bee phylogeny

Historical Biogeography, Divergence Times, and Diversification Patterns in Bumble bees

Our recently published nearly-complete species phylogeny of the bumble bees provides a framework for robustly exploring questions of bumble bee evolution. One of these questions is what extant distributions of taxa and their phylogenetic relationships can reveal about the historical biogeographic patterns and the climatic and geographic factors that have influenced bumble bee radiation, dispersal, and trait evolution through time. These questions are particularly interesting for bumble bees because of their rather unusual cold adaptations - bumble bees acheive highest diversity in cold temperate and alpine regions of the Holarctic and exhibit facultative endothermy and other behavioral and morphological traits suited to cold climates (for more info on bumble bee distribution visit Williams' Bombus site). To infer their historical biogeography, I assigned categories of extant distribution for each species using the areas of endemicity defined by Paul Williams (1996) and assigned to taxa on his Bombus website. Historical areas were then reconstructed against the phylogeny using the program DIVA. To put these reconstructed distributions in a temporal context bumble bee divergence times were inferred using a combination of fossil outgroup dates and known ecological constraints and dates for bees. Furthermore, having nearly-complete species sampling allows assessment of not just historic events, but also the patterns of diversification across time, which I assessed using lineage-through-time plots and related statistics. This study (Hines, 2008) revealed numerous (~18) phylogenetically independent dispersal events of bumble bees from the Old to New World dating after 15-20 million years ago (Mya), with a majority of events occurring in the last 5 My. Only a few dispersal events were inferred in the reverse direction and were estimated to have taken place in the last 3-4 My. Similarly, all except one of the seven inferred dispersal events between North America and South America occurred from north to south and the early events are highly likely to predate the 3 Ma formation of the Panamanian isthmus, with earliest estimates from 7-15 Mya. Diversification patterns reveal a tendency for slightly declining rates of diversification across the phylogeny. There is evidence for leaps in diversification both around the time of entry into the New World and ~ 3 Mya, a time of changing connections between the continents and expansion of cold temperate climates southward.

Nest architecture of Bombus pullatus

While bumble bees are primarily a cold temperate group, a few species live in the hot, moist conditions of the tropical rainforest. In July, 2005 I traveled to Costa Rica to study a nest of one of these species, Bombus pullatus. Only a few B. pullatus nests have been recorded - an arboreal nest fashioned like paper mache in the leaves of a banana tree (Janzen, 1971), and a nest constructed in the roots of a coffee plant (external nest architecture not described) (Chavarria, 1996). Nests of B. transversalis, an exclusively lowland rainforest bumble bee and sister species to B. pullatus, have been studied by Sydney Cameron and are described on her webpage. The nest I observed was similar to B. transversalis nests in that it was constructed by the bees using small pieces of dead vegetation fashioned into a conical canopy on the forest floor that covered and protected the brood. The nest had five entrances, an exceptional number for bumble bees. So many entrances may result from the ease of creating novel entrances in a grassy structure compared to ground nesters that must rely on preexisting tunnels. We also observed foraging behavior, aggression, incidence of parasitization, and floral preferences of the colony. The bees tended to forage more in the morning, particularly pollen foragers, and each forager tended to collect pollen from only one or two floral morphospecies. B. pullatus foraging from flowers on a hilltop were generalists, visiting most of the available flowers, including tiny ones (gallery of some of the flowers visited below). Foragers showed strong directional flow through nest entrances, tending to enter in the right entrances and exit from the left, and had some individual specificity to the entrance entered. A few bees in the nest were parasitized by conopid larvae, one of which was involved in a fight with a nestmate outside of the nest that ended in the death of the parasitized bee. For more information about this nest read Hines, Deans, and Cameron (2007) and visit the photo galleries below.

  

Evolution of Sociality: Vespidae

Some of the most intriguing aspects of bumble bee behavior and life history, as well as their economic value, result from their primitive eusociality. Through interest in their social behavior, I have established a collaboration with Dr. James Hunt, who has maintained a steady interest and research program studying the evolution of sociality in the vespid wasps. Along with undergraduate Tim O'Connor and with the support of my advisor, Sydney Cameron, I sequenced vespids from each of the subfamilies for 4 nuclear genes to obtain a relatively well-resolved phylogeny of the vespid wasps (Hines et al., 2007). This phylogeny yielded exciting conclusions about the evolution of sociality in the group. While morphological data had provided marginal support for a single origin of sociality in the vespid wasps (Carpenter, 1982, 2003), this molecular data provided strong signal for multiple origins. The Stenogastrinae, which are facultatively eusocial and usually form very small nests when social, came out at the base of the vespid phylogeny. The more highly eusocial Polistinae and Vespinae were more derived in the phylogeny as a sister clade to the solitary Eumeninae, suggesting an independent gain of sociality in this clade from that of Stenogastrinae. This has important implications for the study of social acquisition in these wasps and insects in general. Further insights on social gain in the group will rely on more complete taxon sampling within each subfamily as well as sound knowledge of their natural history.

Expeditions

Burma/Malaysia (July, 2007)

I visited Myanmar(Burma) and Malaysia with Dr. Andrew Deans to collect Bombus trifasciatus and comimics B. breviceps and B. haemorrhoidalis. We collected in the government restricted area around Mount Victoria in Chin State and in the eastern Shan mountains near Kalaw and Inle lake. Exploration of the central Bago Yoma area was fruitless for bumble bees but provided us the opportunity to see elephants at work on teak plantations. Additional highlights from Myanmar include the golden temple-dotted plain in Bagan, taking a skiff through the stilted villages of Inle lake, and walking through Kenpeltet, Chin State amongst children when school let out. In Malaysia we spent 4 days visiting the Cameron Highlands area. Particularly remarkable was the *magical* mossy elfin forest near the top of Gunung Brinchang. Myanmar Photos, Malaysia Photos

Sweden (August, 2006)

I visited Sweden to participate in discussion as part of a bumble bee working group for reclassifying the Bombus subgeneric system, also attended by Dr. Sydney Cameron, Dr. Paul Williams, Dr. Pierre Rasmont, and Dr. Bjorn Cederberg. This workshop was held in Uppsala at the ArtDatabanken Swedish Species Information Centre and was followed by a 3 day trip northwest to Dalarna and Jämtland to collect one of the two Aconitum specialized bumble bee species, Bombus consobrinus. Photo Album

Chiapas, Mexico (December, 2005)

I served as an assistant to Drs. Sydney Cameron, James Nieh, and Remy Vandame, on a recruitment behavior project involving Bombus wilmattae at El Colegio de la Frontera Sur in Tapachula, Mexico. In addition to time in the lab we also hiked up Volcan Tocana, which lies near the border of Guatamala, to collect and excavate a wild nest of B. wilmattae that turned out to be overridden by a gelatinous mass of waxmoth larvae. Photo Album

Costa Rica (July, 2005)

I studied a nest of the bumble bee Bombus pullatus at Pitilla Biological Station, a part of the Area Conservación de Guanacaste in Costa Rica. The discovered nest had a nest archictecture similar to that of the other primarily tropical lowland bumble bee, Bombus transversalis, including a large surface mound of cut vegetation seemingly constructed by the bees. Nest observations were made with the help of Dr. Andrew Deans and for the first few days were performed without bee-suits due to lost luggage. Good thing these bees weren't too aggressive. Trip Album, Nest Photos

Mexican Highlands (September, 2004)

To collect the remaining bumble bee species from Mexico needed for the bumble bee phylogeny, I went on a ten day whirlwind collecting trip in the highlands of Mexico with Mexican collaborator, Dr. Ricardo Ayala. This trip covered the area from Guadalajara east to Mexico City, south to Oaxaca and west to the coast. I fell in love with the exceptional diversity in habitats in this region and wish I could have spent more time exploring. We were able to obtain nearly all Mexican species from the region, included the very locally restricted Bombus trinominatus from the highlands of Oaxaca, and Bombus macgregori from its type locality, the serene and pastoral mountain top of Puerto del Gallo, Guerrero. Photo album

Turkey (August, 2002)

During my first year as a graduate student, I accompanied Dr. Pierre Rasmont and his students at the time, Yvan Berbier and Michael Terzo, on a collecting trip throughout Turkey, hosted by Dr. A. Murat Aytekin. This trip took us throughout the northeast quadrant of Turkey, including the drier central lowlands and into the moist mountains of the far northeast. This trip was incredibly bountiful for the bumble bee phylogeny, yielding ~20 species that went into the final analysis, thanks to the expertise of both Drs. Rasmont and Aytekin in the area. Many of the photos in this gallery were taken by Yvan Berbier. Photo album

Pyrenees (July, 2002)

Prior to the trip to Turkey, I spent a few weeks collecting bumble bees for the phylogeny from the Pyrenees with host and mentor Dr. Pierre Rasmont. There I had the opportunity to interact with many of Pierre's students at what is essentially their summer research station, a little cabin in the mountains. The highlight of this part of the trip was finding a gorgeous male Bombus confusus perching on a stone on a mountaintop. Photo album

Bumble bees of the Midwest

Studies of bumble bees from the Midwestern region have been patchy. Faunistic works on bumble bees of the area exist for Nebraska (Laberge and Webb, 1962; Golick and Ellis, 2006), Wisconsin (Medler and Carney, 1963), and Michigan (Husband et al., 1980). Further observations from the region are reported by Franklin (1912), Mitchell (1962), and Milliron (1971,1973a,1973b), but many states remain surprisingly undersampled. Midwestern bumble bee distribution is particularly interesting because the area represents a junction of several faunistic zones. I have gathered data on the distributions of midwestern species from locality records and report these by state for each linked species below.

Midwestern bumble bees can be broadly split into the following faunistic provinces:

Northern Boreal: B. affinis, B. ashtoni, B. borealis, B. fernaldae, B. insularis, B. perplexus, B. rufocinctus, B. sandersoni, B. ternarius, B. terricola, B. vagans

Western U.S./Rocky Mts: B. appositus, B. bifarius, B. centralis, B. fernaldae, B. huntii, B. insularis, B. morrisoni, B. nevadensis, B. occidentalis, B. suckleyi

East (subboreal latitudes): B. auricomus, B. bimaculatus, B. citrinus, B. impatiens, B. fraternus, B. pensylvanicus, B. variabilis

Trans-U.S.: B. fervidus, B. griseocollis

Illinois Bumble bees

    Downloadable Identification Keys and Resources

I created the keys and field guides below for identifying bumble bee species from Illinois, but they also work for Indiana, Missouri, and most of Iowa. These keys were designed for the website BeeSpotter, and therefore appeal to a non-scientific audience. A few far northern Illinois bumble bees were excluded from the keys because of their rarity and difficulty of identification (namely B. terricola, B. rufocinctus, B. perplexus, and B. ternarius).

Pictoral Identification Key: Females

Pictoral Identification Key: Males

Discriminating Males from Females

Field Guide: Males/Females

Field Guide: By Color Group

Not all flowers in your garden are visited by bumble bees. The following PDF (meant to be printed 2 per page and double sided, then folded) lists some of the preferred garden flowers for bumble bees:

Guide: Create a Bumble bee Friendly Garden

    Photo Gallery

Photos I have accumulated of common local species.

Midwestern Bumble bee Seasonality

In 2001 I spent the summer months (May - July) visiting eight prairie remnants and restorations in Johnson and Cedar County, Iowa and recorded bumble bees and the floral resources they visited. These were then compared to overall measures of floral resources at the sites as well as in the broader landscape to determine which factors may play a role in driving local bumble bee diversity (Hines and Hendrix, 2005). This data showed increased bumble bee diversity where more grassland habitat existed and where generally higher levels of landscape floral resources occurred. This research has provided a great deal of data on seasonal and overall abundances of the species. While this data could stand to be improved by additional cross season records, it provides useful information on the variation among the species in seasonal emergence of queens, workers, and males. Below is a record of total bumble bees of each caste for each species collected during the second half of each month.

Dates of first record of each caste of each species have been noted in faunistic studies from Wisconsin (Medler and Carney, 1963), Nebraska (Laberge and Webb, 1962), and Michigan (Husband et al., 1980), and have been reproduced in the graph below:

From these data sources, several trends can be noted in midwestern bumble bee seasonality:

Queens in the Midwest tend to emerge from mid-April though May. Workers begin to come out in late May - June and males begin to emerge in July. Although Nebraska is at a lower latitude (~40-43° North) than Wisconsin and Michigan (~43-47° North), records of emergence of both queens and males between the states are remarkably similar. Yet, the time of emergence of workers in Nebraska is earlier. It is possible this may result from consistently warm temperatures in the spring and early summer supporting better colony production after nest founding.

B. pensylvanicus queen production is later than the other species. In the Iowa study both B. pensylvanicus and B. fervidus queens were still in the field in high numbers in May, suggesting a later emergence of these species. B. griseocollis and B. bimaculatus appear to have earlier worker production. In the Iowa data, B. bimaculatus was the only species with workers in May and by June both B. griseocollis and B. bimaculatus workers were abundant, while other species were just beginning to produce workers. B. bimaculatus and B. griseocollis are also early male producers. B. vagans males appear to emerge soon after worker production. Finally, B. pensylvanicus and B. fervidus males appear to emerge later - no males were recorded for these species by July in the Iowa study. B. impatiens males also appear later.

Seasonality may play an important role in the decline in abundance of certain species, especially in the face of fluctuating and unusually warm temperatures resulting from global warming. For example, the earlier emerging queens in the spring (in my experience these are B. bimaculatus, B. griseocollis, B. impatiens, and B. affinis, reflected by the above data as well) may have lower abundances in years when there are late spring chills, but may abound and outcompete later emerging species in years where the spring is unseasonably warm. Climate differences from year to year could lead to dramatic fluctuations in bumble bee species abundances across years.

Links

Illinois Natural History Survey Insect Collection Database

University of Kansas Entomology Collection Specify Database

Clemson University Arthropod Museum Database

Global Biodiversity Information Facility

Bumble Boosters: Identification of Nebraska Bumble Bees

The Wisconsin Bumble Bee

Arkansas Bumblebee Survey

Arkansas Bumblebee Guide

References

Franklin, H.J. 1912. The Bombidae of the New World. Transactions of the American Entomological Society. 38:177-486.

Golick, D.A., and M.D. Ellis. 2006. An update on the distribution and diversity of Bombus in Nebraska (Hymenoptera: Apidae). Journal of the Kansas Entomological Society 79: 341-347.

Husband, R.W., Roland L.F., and T.W. Porter. 1980. Description and biology of bumblebees (Hymenoptera: Apidae) in Michigan. The Great Lakes Entomologist 13:225-239.

Laberge, W.E., and M.C. Webb. 1962. The bumble bees of Nebraska. University of Nebraska College of Agriculture, The Agricultural Experiment Station Research Bulletin 205:1-38.

Medler, J.T., and D.W. Carney. 1963. Bumblebees of Wisconsin (Hymenoptera: Apidae). University of Wisconsin Research Bulletin 240: 1-42.

Milliron, H.E. 1971. A monograph of the Western Hemisphere bumblebees (Hymenoptera: Apidae; Bombinae) I. The genera Bombus and Megabombus subgenus Bombias. Memoirs of the Entomological Society of Canada 82:iii-80.

Milliron, H.E. 1973. A monograph of the Western Hemisphere bumblebees (Hymenoptera: Apidae; Bombinae) II. The genus Megabombus subgenus Megabombus. Memoirs of the Entomological Society of Canada 89:81-237.

Milliron, H.E. 1973. A monograph of the Western Hemisphere bumblebees (Hymenoptera: Apidae; Bombinae) III. The genus Pyrobombus subgenus Cullumanobombus. Memoirs of the Entomological Society of Canada 91:239-333.

Mitchell, T.B. 1962. Bees of the Eastern United States Volume II. The North Carolina Agricultural Experiment Station, Technical Bulletin No. 152.

Publications