Host Developmental Stage and Size as Factors Affecting Parasitization of Trogoderma variabile (Coleoptera: Dermestidae) by Laelius pedatus (Hymenoptera: Bethylidae)

Abstract

Host acceptance and parasitization of the warehouse beetle, Trogoderma variabile Ballion, by the ectoparasitic wasp Laelius pedatus (Say) were affected by host developmental stage and size. Larvae <2.5 mm long or 0.4 mg in weight were not parasitized, although a few were paralyzed. Clutch size was positively correlated with host size but was limited on large hosts by the finite number of mature eggs available for oviposition. The maximal clutch size was six eggs during a 1-d exposure and nine eggs when the host(s) was exposed for 3 d. Female wasps showed no host size preference in a choice test. Inexperienced females 3—7 d after emergence produced either 0 or one male progeny per clutch, and never was more than one male offspring per host observed. Females attacked and parasitized host pupae, but handling time before deposition of eggs was significantly longer than larval handling time because of additional time spent penetrating the protective larval exuviae before stinging. Newly molted pupae were readily paralyzed and accepted for oviposition until tanning of the adult elytra occurred. The percentage accepted for oviposition decreased gradually during the last day of the pupal stage, and no pharate adults were developmentally arrested or parasitized. Nevertheless, pupae, in addition to larvae, are parasitized by L. pedatus , and the potential value of this wasp as a biological control agent may be greater than previously thought.