The endoparasite Microctonus pachylobii was discovered parasitizing a new weevil host, Hylobius radicis. Thirteen of the 154 H. radicis adults collected were parasitized (8.5%). The median numbers of parasites per weevil were 26 (x =22.5) during the period April through June, and 4 (x =9.4) during August and September. The median male:female sex ratio was 0.91 (x =0.65). Males emerged approximately 1 day earlier than females. Median parasite mortality while in the cocoon was 10.2% per parasitized weevil (x = 11.8%). Microctonus pachylobii was not found parasitizing two previously recorded weevil hosts from field samples, Hylobius rhizophagus and H. pales, and a laboratory study suggests that the parasite may have difficulty parasitizing the latter species.
Hoffman, George D. and Raffa, Kenneth F.
"Microctonus Pachylobii (Hymenoptera: Braconidae): New Host Record From Hylobius Radicis (Coleoptera: Curculionidae), and Additional Notes on Its Biology,"
The Great Lakes Entomologist, vol 26
Available at: https://scholar.valpo.edu/tgle/vol26/iss1/6