It is easy to determine the sex in most acuelate Hymenoptera (ants, bees and wasps). In these Hymenoptera the female typically has 12 antennal segments and the male has 13. In Bombus, as with many bees, males can also be distinguished by their noticeably longer antennae. Some male Bombus also have larger eyes than females.
| Males have longer antennae than females. | |
|---|---|
| Female | Male |
|
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One should be sure that the specimen being examined is of the genus Bombus, not a member of the closely related genus Psithyrus. Psithyrus females are social parasites of Bombus females. They do not collect pollen, instead they enter Bombus nests and lay their eggs in Bombus pollen masses. Because Psithyrus females do not collect pollen, they lack the pollen carrying corbiculae on the hind tibiae, which Bombus have. The presence or absence of the corbiculae is a good way to determine the genus of female specimens.
| The hind tibiae of Bombus and Psithyrus females | |
|---|---|
| Bombus | Psithyrus |
 |
 |
| Corbiculae present | Corbiculae absent |
Page author: Matthew P. Kweskin
Last modified: 31 Mar 1997
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