Subject: Black and Yellow Wasp
Location: Trinity Alps, California
August 24, 2013 6:50 pm
Hi. This guy was on a Zinnia blossom today. I think it may be a Yellow Jacket but it doesn’t seem quite right. This is larger than the Yellow Jackets around here. About an inch long. Seemed to be collecting pollen or laying eggs. Thanks for your help.
Signature: Karen Horn
This is a Sand Wasp in the tribe Bembicini and probably the subtribe Bembicina. According to BugGuide: “About three quarters of the species prey on Diptera, and it is believed that fly predation is ancestral in the group; the rest prey on Lepidoptera, Hymenoptera, Neuroptera, Odonata, and/or Homoptera.” We believe your individual is in the genus Bembix and BugGuide has some interesting information on these Sand Wasps, including: “Females provision their nest with flies which the larvae feed on (a single developing larva may eat more than twenty flies)” and “Provisioning is progressive. The females provide a greater number of prey over subsequent days during larval growth. Adults are excellent diggers and can disappear below the surface of loose sand within seconds.” We know of a freeway overpass in in industrial part of downtown Los Angeles that is about as far away from a natural area as one can get. The sandy soil under that freeway is populated by Sand Wasps each summer and we suspect they play an important role in the control of the fly population in the vicinity.
Thank you so much for your reply!
One question: Are they pollinators? Do they collect pollen? Mine was very busy in that Zinnia and I noticed several other pictures on your website with the Sand Wasps on flowers.
Thanks again, Karen Horn
Adult Sand Wasps do visit flowers for nectar. Like many adult wasps, Sand Wasps take nectar, but they hunt insect prey for the developing larvae.