Most notably, C. validus males and females have an exaggerated malar space, giving the impression of a long, triangular face.

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.

[3] C. validus is a univoltine bee that flies in early spring, coinciding with the flowering of Vaccinium and other ericaceous plants.

[1] Near the southern extent of its range, adults fly in late-March, whereas further north flight occurs three to four weeks later.

[4] Males disappear from the aggregation two to three weeks after emergence, leaving females as the only flying C. validus at the end of the season.

Anecdotal evidence from nests excavated early March[1] suggests that some prepupae (fully developed larvae) enter diapause before pupating.

Nests can be found on flat ground or south-facing slopes, but rarely under a closed canopy since C. validus prefers warm soils.

[1] 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.

and it will forage for pollen broadly on a diversity of ericaceous plants with urceolate flowers, e.g. bearberry (Arctostaphylos uva-ursi) and black huckleberry (Gaylussacia baccata).

pollen and males and females have been observed visiting non-ericaceous plants (e.g. Acer rubrum, Prunus spp., Amelanchier spp.)

[4] Tunnel walls are not compacted since C. validus lacks a pygidial plate normally used for tamping down soil (a trait shared by all Colletes).

[4] She proceeds by “painting” a Dufour's gland secretion mixed with saliva onto the walls of the cell using her short, bilobed glossa.

[1] Bee flies (Bombylius mexicanus, B. pygmaeus in Beltsville, MD) have been observed ovipositing in the nest entrances of Colletes validus, but no larvae have been recovered from cells.

C. validus can nest on footpaths through sand plain preserves or in open backyards built on sandy oak-pine forests (e.g. Barnstable County, Massachusetts), resulting in possible conflict with humans and pets.