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Megachile rotundata

Resource Type
Common Name
alfalfa leafcutting bee

The alfalfa leafcutting bee, Megachile rotundata F. (Megachildae) is a Eurasian solitary bee species that was inadvertently introduced to North America sometime before the 1940s. By the mid 1950s, M. rotundata had become established in the farming regions of western United States. With the discovery of M. rotundata’s pollination impact on alfalfa seed production, early efforts to increase its populations near alfalfa fields were undertaken a few years later. Currently, M. rotundata is the most intensely managed solitary bee species in the world and is surpassed only by the honey bee for its economic impact.

Females are gregarious cavity nesters constructing nests composed of leaf pieces in a linear series of cells in naturally occurring cavities or in artificial nesting boards. In most North American latitudes, M. rotundata emerge in late June and early July. Females provision each cell with nectar and pollen, lay a single egg and seal the cell before starting the construction of the next cell. The larvae will develop through five larval instars, spin a cocoon and enter a prepupal diapause and overwinter. A portion of the larvae laid in early spring will avert diapause and produce a second generation of bees. The second generation is problematic to farmers. Depending on the length of the growing season the larvae of the summer generation of females may enter diapause and overwinter. Therefore, in some years the second generation will result in an increased number of bees entering diapause and available for the next growing season. But if the growing season is too short, the larvae will not have sufficient time to complete development and will not be able to enter diapause. Besides influencing the total number of bees entering diapause each year, the second generation has been implicated as a major factor in the spread of chalk brood, the primary disease of M. rotundata. The development of a M. rotundata genome database is an important advancement for understanding basic physiology and disease management of this important pollinator.

Kapheim KM, Pan H, Li C, Salzberg SL, Puiu D, Magoc T, Robertson HM, Hudson ME, Venkat A, Fischman BJ, Hernandez A, Yandell M, Ence D, Holt C, Yocum GD, Kemp WP, Bosch J, Waterhouse RM, Zdobnov EM, Stolle E, Kraus FB, Helbing S, Moritz RF, Glastad KM, Hunt BG, Goodisman MA, Hauser F, Grimmelikhuijzen CJ, Pinheiro DG, Nunes FM, Soares MP, Tanaka ÉD, Simões ZL, Hartfelder K, Evans JD, Barribeau SM, Johnson RM, Massey JH, Southey BR, Hasselmann M, Hamacher D, Biewer M, Kent CF, Zayed A, Blatti C, Sinha S, Johnston JS, Hanrahan SJ, Kocher SD, Wang J, Robinson GE, Zhang G. Social evolution. Genomic signatures of evolutionary transitions from solitary to group living.. Science (New York, N.Y.). 2015 Jun 05; 348(6239):1139-43.
Organism Image
Image Credit
Theresa Pitts-Singer, U.S. Department of Agriculture. Public domain.
NameProgramDate Constructed
Megachile rotundata NCBI Annotation Release 101NCBI Eukaryotic Genome Annotation PipelineMar 23rd, 2016
Megachile rotundata genome assembly MROT_1.0 (GCF_000220905.1)SOAPdenovo AssemblerMar 23rd, 2016
Megachile rotundata gene predictions v1.1CustomMay 4th, 2016
Functional annotation of NCBI Megachile rotundata Annotation Release 101AgBase functional annotation pipelineApr 22nd, 2022
Diapause development RNAseq, combined assemblyTuxedo Suite (TopHat2 v2.0.10/Cufflinks v2.1.1/Cuffmerge v1.0.0)Nov 17th, 2017
Assembly Stats
Contig N50
Scaffold N50
GC Content
Other Information
Community Contact
  • George Yocum|George.Yocum@ARS.USDA.GOV
  • Karen Kapheim|
  • Hailin Pan|