J. Alcock, Sleeping aggregations of the bee Idiomelissodes duplocincta (Cockerell) (Hymenoptera : Anthophorini) and their possible function, J KAN ENT S, 71(1), 1998, pp. 74-84
Males of the bee Idiomelissodes duplocincta roost in the evening together o
n the stems of desert shrubs during months in central Arizona. The size of
the aggregation can vary greatly during the few days to several months when
a shrub is being used as a sleeping site. Some males return to the same pl
ant for up to two weeks but show little site fidelity ta a particular stem.
When frequently-occupied stems are experimentally cut and moved to new sit
es in a shrub and replaced with other stems of similar dimensions, the bees
rarely utilize: the replacement stems but instead shift elsewhere or seek
out the previously popular stems In their new locations. This result sugges
ts that odor cues applied by sleeping bees (or some other special propertie
s of the favored stems) attract male bees coming to specific roost sites. S
leeping aggregations are occasionally visited by a predator of the bees, th
e assassin bug Apiomerus flaviventris. However, the number of assassin bugs
present at any one aggregation on a given evening is small (not exceeding
four in the present study), and few bees are taken. Sleeping bees do not at
tack or harass the assassin bug. Moreover, they usually ignore approaching
assassin bugs rather than flee, even when the predator vigorously attempts
to subdue a neighboring bee on a sleeping stem. Thus, male bees in sleeping
aggregations apparently gain anti-predator benefits largely through the di
lution effect.