Microctonus Pachylobii (Hymenoptera: Braconidae): New Host Record From Hylobius Radicis (Coleoptera: Curculionidae), and Additional Notes on Its Biology

Abstract

The braconid Microctonus pachylobii was discovered parasitizing a new weevil host, Hylobius radicis, during studies in a pine [Pinus] plantation in central Wisconsin in 1991. Thirteen of the 154 H. radicis adults collected were parasitized (8.5%). The median numbers of parasitoids per weevil were 26 during the period April-June, and 4 during August-September. The median male:female sex ratio was 0.91. Males emerged approximately 1 day earlier than females. Median parasitoid mortality while in the cocoon was 10.2% per parasitized weevil. M. pachylobii was not found parasitizing 2 previously recorded weevil hosts, H. rhizophagus and H. pales, from field samples, and a laboratory study indicated that the parasitoid may have difficulty parasitizing the latter species.