Passaloecus gracilis 

Taxonomy
Passaloecus are aphid wasps in the family Crabronidae. They are known for their large mandibles in which they carry prey back to their nests. These mandibles are also used in clearing debris out of nesting sites. In Minnesota, the genera represented inhabit the Holarctic and Nearctic regions. Passaloecus gracilis is considered to be in the gracilis group of species.

Description
Passaloecus gracilis is a medium-sized species of the genus Passaloecus, reaching up to 7mm in length. They possess black bodies with appendages ranging in color from black to orange-brown. P. gracilis can be distinguished from other Passaloecus species by having a scutum (the dorsal surface of the thorax) with raised lines across it that are broken up into segments. There are grooves extending halfway across the back. Near the side of the body, there is a smooth area separating two indented lines. Unlike other species, P. gracilis do not have faces with distinct areas marked by the pattern of hairs, and the hairs point downwards.

Nest Structure
The female wasps construct their nests inside dry, hollow plant stems and abandoned beetle tunnels in decaying wood. They also sometimes nest within the unusual plant growths called "galls" that form on oak trees due to the Andricus kollari gall wasp. However, not much else is well understood about the details of their nesting behavior and requirements.

Hole Sizes
No information at this time. 

Voltinism
This species appears to be univoltine throughout its range, completing one generation per year in Minnesota.

Activity
No information at this time.

References
Lomholdt, O. 1984. The Sphecidae (Hymenoptera) of Fennoscandia and Denmark. Fauna Entomologica Scandinavica 4. 

Vincent, D. L. 1973. A revision of the genus Passaloecus (Hymenoptera: Sphecidae) in America north of Mexico. The Wasmann Journal of Biology, 36(1 & 2): 127-198.