This is the first study of the nesting ecology of Megachile (Pseudocentron) alleni, a common ground-nesting solitary bee found throughout the Bahamas. While apparently an important pollinator in coastal communities, very little is known about its nesting behavior. Previously, we observed females collecting three plant resources: nectar, pollen, and leaves. We hypothesized which plants would be used for nectar and which for pollen based on the architecture of the floral display and observations of insect behavior. To test these hypotheses, we isolated and identified pollen occurring in cocoons from nest cells.

We observed 412 interactions between M. alleni individuals and the flowers of 26 plant species in 14 families. Fifteen pollen species were identified from 15 dissected cocoons; cells averaged 5.5 pollen species ±1.7 SD. Two-thirds of the cocoons contained pollen from three species (Corchorus hirsutus, Jacquemontia cayensis, and Lantana involucrata), and more than half of the pollen species were found in at least twenty-seven percent of the cells. We found pollen from eight of the hypothesized sources, but also pollen from four species hypothesized to provide only nectar, and from three species not previously recognized as floral resources. Leaves of at least four species were used for nest cell construction.

Females searching for suitable nests flew over the ground, often searching in cavities under rocks or asphalt. Substrate under 52 nests was usually light sand (78%) or darker sand with humus (16%). Nests averaged 2.88 cells ±2.0 SD (N  =  37). Actively nesting females made numerous provisioning trips daily, each preceded by a brief orientation flight. One female was observed carrying leaf pieces, and later pollen, into her nest. On average, she spent 50% more time in the nest and 150% more time away from the nest while handling pollen. We observed one species of beefly parasitizing the nests.