Date of Award

1991

Degree Type

Thesis

Degree Name

Master of Science in Plant Pathology-Entomology

Department

Plant Pathology-Entomology

First Advisor

Patrick Logan

Abstract

I investigated the biology of the Mexican carabid, Lebia subgrandis Madge, a potential biological control agent of the Colorado Potato Beetle (CPB), Leptinotarsa decemlineata (Say). The consumption of CPB eggs and 1st through 3rd instar larvae increased with temperature for both male and female L. subgrandis. Under laboratory conditions, confined pairs consumed up to 108 CPB eggs / day at 28°C (mean = 44.5 CPB eggs / day). Early-summer females produced more offspring than late-summer females. Apparently, mating was infrequent; I found no difference in oviposition rates when the females were confined with males for 0, 1, 2, or 3 days, or for the entire experiment. First instar L. subgrandis larvae lived an average of 8.3 days. They are ectoparasites of CPB prepupae and pupae and actively seek their hosts in the soil.

Adult L. subgrandis seek their prey both day and night. The host range is narrow: previously starved or not, this species refused eggs and larvae of Coleomegilla maculata DeGeer, and eggs and nymphs of either Oplomus sp. or a reduviid predator. Adults lived four to five months. Reproductive capacity was temperature dependent. L. subgrandis might be considered as a candidate to control the CPB in the northeast U.S.

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