Biology and development of Laricobius kangdingensis Zilahi-Balogh and Jelinek, a newly discovered predator of Adelges tsugae

The biology and temperature-dependent development of Laricobius kangdingensis Zilahi-Balogh and Jelinek (Coleoptera: Derodontidae), a newly described predator of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae) were investigated and compared with a related HWA predator, L. nigrinus Fender, that has already been released. As with other Laricobius species, there are four larval instars. The female to male sex ratio was 1:1.1. Mean lifetime fecundity per female was 196.4 eggs and 97.9 eggs for the parental generation (P-1) and first filial generation (F-1), respectively. Developmental rates at 6, 9, 12, 15, and 18A degrees C were studied between fall 2002 and spring 2004 and used to determine low temperature development thresholds for the egg (2.8A degrees C), and larval (1.6A degrees C) stages. The egg and larval thresholds are lower than those observed for L. nigrinus. Laricobius kangdingensis individuals completed development only at 12 and 15A degrees C; however, the adults did not emerge from aestivation after pupation. Our results suggest that L. kangdingensis may be a promising addition to the complex of predators currently being reared for control of HWA. Laricobius kangdingensis is long-lived, exhibits high fecundity, and can complete development on North American HWA. However, further studies will be necessary to secure its clearance for release, and the source of high mortality in the laboratory must be identified in order to improve its survival for mass-rearing.