Suitability of Various Artificial Pupation Chambers for use by Koinobiont Parasitoid Toxoneuron nigriceps (Hymenoptera: Braconidae)

Abstract

Abstract Although koinobiont parasitoids depend on their hosts for nutrition, they often exploit them in other ways during pupation. The solitary endoparasitoid Toxoneuron nigriceps Viereck (Hymenoptera: Braconidae) spins its cocoon in a chamber formed by its host Heliothis virescens (F.) (Lepidoptera: Noctudidae). The parasitoid prepupae depend on this host-formed pupation chamber; if left on an open surface, T. nigriceps larvae are unable to form a cocoon. To determine whether T. nigriceps larvae can form cocoons in artificial pupation chambers, common laboratory materials were tested for suitability. Test chambers included cotton balls, upright test tubes, gelatin capsules, and the wells of microtube racks. The proportion of parasitoids that formed cocoons in each chamber, as well as the proportion that survived to adulthood, were recorded and compared with each other and to those placed in host-formed chambers, as well as to those placed in petri dishes, a flat surface. Parasitoid larvae were able to spin cocoons in all artificial chambers that provided a small, partially enclosed space. The proportion of parasitoids that formed cocoons was largest in cotton balls, but no chambers (other than petri dishes) were significantly different from the host formed control. The proportion of parasitoids that survived to adulthood was significantly smaller in the petri dish and test tube treatments than in the control. Due to the high success rate for cocoon formation and survival, as well as practicality in a mass-rearing situation, gelatin capsules and microtube rack wells were considered the best choices for use as artificial pupation chambers among those tested.