We compared female nest usurpation and size variation in a population of the introduced leaf-cutter bee Megachile apicalis Spinola. Both behavioral and morphological evidence was gathered from three types of females: 1) those that occupy and defend nest holes, 2) those that patrol the nesting substrate while attempting to displace the latter group and 3) pollen-foraging bees that apparently had already established nests elsewhere in the environment. Females occupying holes and patrolling nesting sites were, on average, larger than foraging females. In addition, female densities at nest sites correlated positively with the average size of females found at those sites.
Barthell, John F. and Thorp, Robbin W., "Nest Usurpation Among Females of an Introduced Leaf-Cutter Bee, Megachile Apicalis" (1995). Ba. Paper 77.
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