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Passaloecus annulatus (aphid wasp/square headed wasp)
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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. P. annulatus is considered to be in the annulatus group of species.
Description
Passaloecus annulatus are medium-sized species of Passaloecus, usually about 5mm in length. They have black bodies with flagellomeres that are banded with white or pale yellow. They have large hind trochanters that are pale amber. Two characteristics that set P. annulatus apart from others are a large, truncate clypeal lobe and the complete absence of a scrobal sulcus. Both female and male P. annulatus wasps have bidentate mandibles, but the mandibles of the females are broader and less sharp.
Nest Structure
Passaloecus annulatus build their nests in the stems of plants – most commonly in the stems of Smooth Sumac and Eastern Black Walnut trees. They are also known to inhabit abandoned beetle galleries or, in the case of the Minnesota Bee Atlas, holes in wood blocks. P. annulatus partition these cells with resin and provision them with aphids.
Hole Sizes
No information at this time.
Voltinism
This species appears to be univoltine in the Midwest, completing one generation per year in Minnesota. However, it appears that this species may be multivoltine in warmer climates.
Activity Period
Passaloecus annulatus are active in Minnesota from April to September.
References
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.
Minnesota Record Map
These data are from the Minnesota Bee Atlas project.
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