Blueberry Cellophane Bee

Appearance

''C. validus'' is a medium-sized cellophane bee: females are 13-14mm long and males are 10-12mm long. As is the case with members of the genus ''Colletes,'' all individuals have an “S”-shaped 2nd recurrent vein on the forewing. Most notably, ''C. validus'' males and females have an exaggerated malar space, giving the impression of a long, triangular face. These two characteristics are diagnostic for ''C. validus'' within its range. Males are covered densely with brown-yellowish hairs, giving fresh individuals a golden tinge. Females are less hairy and have reduced, but present scopa on the hind legs. It is similar to ''C. inaequalis'' Say and ''C. thoracicus'' Smith in appearance, range and phenology, however both of these species lack the distinctive long face.

Distribution

Its range extends from the Mid-Atlantic states north through New Hampshire and west through Michigan, with sparse records west to Wisconsin and north to Ontario. ''C. validus'' is found throughout this range in sandy areas in proximity to ericaceous plants. Records from Georgia and Florida likely belong to a newly described species, ''C. ultravalidus.''

Behavior

Nests descend from 17–60 cm and measure ≈8mm in diameter. Tunnel walls are not compacted since ''C. validus'' lacks a pygidial plate normally used for tamping down soil . Cells are constructed at the end of short lateral tunnels arranged radially around the main tunnel. Laterals are constructed from the bottom to the top. She proceeds by “painting” a Dufour's gland secretion mixed with saliva onto the walls of the cell using her short, bilobed glossa. This mixture polymerizes into a polyester- or cellophane-like substance, which is where bees in the genus ''Colletes'' get their common name. Cell construction primarily occurs at night and provisioning of the cell follows the next morning. To provision the cell, the female first forages for ericaceous pollen and packs it into the bottom third of the cell. Next, she adds nectar until a viscous soup is formed. The waterproof cellophane lining of the cell permits the usage of semi-liquid provisions. Bacteria '' and/or yeast likely colonize the provisions based on visible gas bubbles and sour taste . Fermentation is common in other colletids that create liquid provisions, e.g. ''Ptiloglossa guinnae''. The female hangs a single egg from the top of the cell so that the egg is not submerged in the provisions. A maximum of five cells have been associated with any given nest. It is unknown whether females create more than one nest during their lifetime.

Habitat

''C. validus'' is a gregarious nester, meaning that nests often occur in aggregations . Nesting sites are located in open sandy soils with sparse vegetation, often located close to their ericaceous hosts. Nests can be found on flat ground or south-facing slopes, but rarely under a closed canopy since ''C. validus'' prefers warm soils. Dense grass deters nesting.

Surprisingly, ''C. validus'' is completely absent from surveys in the lowbush blueberry fields of Maine despite the tremendous abundance of host plant and presence of its generalist congener, ''C. inaequalis''. One explanation is that cold springtime soils discourage nesting, but this hypothesis has not been rigorously tested. Clearly, there are other factors besides open, sandy soil and host plant presence determining the nesting of ''C. validus'' within its range.

Defense

''C. validus'' is a gregarious nester, meaning that nests often occur in aggregations . Nesting sites are located in open sandy soils with sparse vegetation, often located close to their ericaceous hosts. Nests can be found on flat ground or south-facing slopes, but rarely under a closed canopy since ''C. validus'' prefers warm soils. Dense grass deters nesting.

Surprisingly, ''C. validus'' is completely absent from surveys in the lowbush blueberry fields of Maine despite the tremendous abundance of host plant and presence of its generalist congener, ''C. inaequalis''. One explanation is that cold springtime soils discourage nesting, but this hypothesis has not been rigorously tested. Clearly, there are other factors besides open, sandy soil and host plant presence determining the nesting of ''C. validus'' within its range.Nests descend from 17–60 cm and measure ≈8mm in diameter. Tunnel walls are not compacted since ''C. validus'' lacks a pygidial plate normally used for tamping down soil . Cells are constructed at the end of short lateral tunnels arranged radially around the main tunnel. Laterals are constructed from the bottom to the top. She proceeds by “painting” a Dufour's gland secretion mixed with saliva onto the walls of the cell using her short, bilobed glossa. This mixture polymerizes into a polyester- or cellophane-like substance, which is where bees in the genus ''Colletes'' get their common name. Cell construction primarily occurs at night and provisioning of the cell follows the next morning. To provision the cell, the female first forages for ericaceous pollen and packs it into the bottom third of the cell. Next, she adds nectar until a viscous soup is formed. The waterproof cellophane lining of the cell permits the usage of semi-liquid provisions. Bacteria '' and/or yeast likely colonize the provisions based on visible gas bubbles and sour taste . Fermentation is common in other colletids that create liquid provisions, e.g. ''Ptiloglossa guinnae''. The female hangs a single egg from the top of the cell so that the egg is not submerged in the provisions. A maximum of five cells have been associated with any given nest. It is unknown whether females create more than one nest during their lifetime.