|Aphid Wasps – Subfamily Pemphredoninae, Tribe Psenini
Order Hymenoptera – Ants, Bees, Wasps and Sawflies
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Live pair of aphid wasps photographed at Winfield, Illinois. Size – Female = 12mm, male = 10mm
This pair eventually tired of me and flew away in tandem. I never got a photograph of them actually mating.
Subfamily Pemphredoninae consists of about 1050 species in 40 genera worldwide . The pemphredonines are small to tiny sphecids, many of which display one or more of the following distinctive characteristics: A stemlike sternal petiole (the proverbial "wasp-waist"), a cuboidal head (many wasps in the parent family Crabronidae are commonly called "square-headed" wasps), and a disproportionate enlargement of the forewing stigma .
Other identifying characteristics:
Petiole usually consists of sternum 1 only. Males exhibit 7, and females 6 gastral segments.
Pemphredonines are often abundant, but being rather small and adept at hiding (the pair pictured here were hidden underneath a leaflet when I spied and uncovered them), I don't see many of these, and I consider myself fortunate to have encountered a cooperative couple; it's usually futile to chase one of these wasps while they are nectaring or hunting, they just won't hang around long.
Wasps in the tribe Psenini (psenins), like these, are between 4 and 15mm long. All have a distinct wasp-waist, the aforementioned petiole made up entirely of the first sternum. Female psenins are more liberal in their choice of prey, using mostly cicadellids, fulgoroid, membracid, cercopid, or psyllid planthoppers.
Pemphredonines are represented in the early fossil record in a find at Cedar Lake, Manitoba, Canada, of a specimen in the genus Lisponema in Upper Cretaceous (965-100 mya) amber .
The dense, silvery pile covering the thorax is also found on wasps in the tribe Psenina .
Hymenoptera (Latin for membrane wing) is a vast assemblage of insects second only to Coleoptera (beetles) in the number of described species. Hymenoptera number some 115,000 species – of which 18,000 live in North America. Hymenopterans inhabit a wide variety of habitats, and show an incredible diversity in size, behavior, structure and color.
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