Development and reproductive biology of Laricobius nigrinus, a potential biological control agent of Adelges tsugae

Biological studies on Laricobius nigrinus Fender (Coleoptera: Derodontidae) were conducted in the laboratory to obtain basic information on this little known predator. Laricobius nigrinus is a candidate biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), an exotic pest on eastern (Tsuga canadensis (L.) Carriere) and Carolina (T. caroliniana Engelmann) hemlocks in the eastern United States. It is univoltine and undergoes an aestival diapause. Post-aestivation activity period was 36.6 and 30.8 weeks for males and females, respectively. Adult activity and oviposition are well synchronized with the over-wintering generation of A. tsugae. Mean lifetime fecundity was 100.8 eggs over a mean duration of 13.2 weeks oviposition period. Within the temperature range (12-18 degreesC) studied, development was fastest at 18 degreesC. Mean development time from egg to adult was 88.8, 64.8 and 46.6 days at 12, 15 and 18 degreesC, respectively. Laricobius nigrinus has four larval instars. Mean larval consumption was 225.9 and 252.3 A. tsugae eggs at 12 and 18 degreesC, respectively. These findings provide essential data on the rate of development and feeding capacity of L. nigrinus at temperatures typical of ambient conditions during late winter/early spring in Virginia. Its rapid development at 18 degreesC indicates that it has potential as a biological control agent of A. tsugae because of its synchrony with the development of the over-wintering generation of A. tsugae in eastern United States.