The Biology of Campoplex haywardi (Hymenoptera: Ichneumonidae), A Primary Parasite of the Potato Tuberworm1

Abstract

Campoplex haywardi Blanchard, a solitary, internal parasite of larvae of the potato tuberworm, Phthorimaea operculella (Zeller), was studied under insectary conditions of approximately 80°F and 50% RH. Its white, slightly curved eggs, averaging 0.27×0.12 mm, had an incubation period of 2–3 days in the host's body cavity, where the larvae developed. Larvae spent 3 days in the first instar, 2 in the second, and 2–3 clays in the third instar; these instars differed distinctly in shape and mandibular size. Mature larvae normally emerged from hosts after the latter had spun cocoons; their own cocoons, averaging 5.5×1.8 mm, were spun inside those of the hosts. With the minimum pupal period 7 days, the shortest interval between egg deposition and adult emergence was 17 days. More than half the adults emerged within 19 days, but total developmental time reached 23 days for some females and 28 days for some males. Copulation took place soon after emergence of either sex, and the female's preoviposition period was less than 24 hr. Females over 24 hr old were rather reluctant to mate, and those over 3 days old often rejected pursuing males. The oviposition sequence began with the female tapping the potato surface with her antennae, locating and examining frass deposited by burrowing tuberworm larvae. When the tunnel opening had been located by probing with the ovipositor, the ovipositor was inserted into it to find the host and deposit an egg in it. Oviposition was accomplished in 1–2 sec. Adult life was longest in groups given water and honey, averaging 13.8 and 18.3 days (maximum 28 and 36 days) for males and nonovipositing females, respectively. Adults not given food or water survived 3 days at most. Four unmated females of this arrhenotokous species had an average adult longevity of 15.3 days and produced an average of 60.3 male progeny. Eight mated females had an average oviposition period of 9.25 clays (maximum 16 days) and produced an average of 87.3 progeny of both sexes (maximum 143). These 8 females had an average adult longevity of only 10.5 days (maximum 19 days), and the sex ratios (♂/♀) of their respective groups of progeny ranged from 0.05 to 1.93, with an average of 0.65.