Rhorus

Taxonomy

Rhorus varifrons are parasitic wasps belonging to the family Ichneumonidae and the subfamily Ctenopelmatinae. They are also known as the thread-waisted wasp. Vari" can mean various or different, and "frons" means front or forehead. So, "varifrons" might imply variability or differences in the front part of the insect, possibly referring to distinctive features of its head or face. R. varifrons is primarily found in the southeastern United States, particularly in states like Florida, Georgia, Alabama, and Mississippi. Its range may extend into neighboring states as well. This makes it a rarity to be found in Minnesota. We only had one Rhorus varifrons in the Bee Atlas project. It emerged from a block located in Duluth, St. Louis County in 2017.

Description

Rhorus varifrons, commonly known as the thread-waisted wasp, exhibits distinct anatomical characteristics more typical of the family Sphecidae than the family Ichneumonidae. These wasps typically measure between 10 to 15 mm in length, with a slender, elongated body and a notably narrow waist, hence the common name "thread-waisted." They have well-developed wings with intricate venation patterns, allowing for agile flight. The head is equipped with large compound eyes and thread-like antennae used for sensory perception. Their mandibles are adapted for capturing and manipulating prey. The thorax, which bears the wings and legs, is robust, providing strength for flying and hunting activities. The abdomen is elongated and often displays intricate color patterns of blacks, yellows, red, and oranges, contributing to their visual appeal. 

Nest Structure

Like most Ichneumonids, Rhorus varifrons do not build their own nests. Instead, they parasitize the nests of other insects. R. varifrons is known to parasitize various various types of insects, including caterpillars, beetle larvae, flies, sawflies, and other insects in the larval or pupal stage. The only other insect that emerged from the same nest as the Rhorus varifrons was a common sawfly in the family Tenthredinidae. 

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 Period

No information at this time.

References

BugGuide.Net. (n.d.). Rhorus varifrons - BugGuide.Net. Retrieved from https://bugguide.net/node/view/337821/bgpage

Cummins, H. M., Wharton, R. A., & Colvin, A. M. (2011). Eggs and egg loads of field-collected Ctenoplematinae (Hymenoptera: Ichneumonidae): evidence for phylogenetic constraints and life-history trade-offs. Annals of the Entomological Society of America, 104(3), 465-475.

Discover Life. 2024. "Ichneumonidae." In Proceedings of the Ecological Society of America, vol. 6. Accessed May 30, 2024. https://www.discoverlife.org/proceedings/0000/6/html/Ichneumonidae.html 

Thank you to John Luhman for identifying all of our Ichneumonid specimens.