Abstract
The developmental biology of a tachinid parasitoid (Gymnosoma rotundatum) and the effects of its parasitism on reproduction of the host, the brown-winged green bug (Plautia crossota stali), were studied. The tachinid females laid eggs on the abdominal tergum of the hosts and larvae penetrated into and developed in their body cavities. A single mature larva exited from each of the hosts and pupariated. Even in cases when the fly deposited two eggs onto a host, only one maggot survived to maturity. The hosts died within a day after the maggot emerged. The percentage of larvae emerging from hosts, larval duration, and puparial weight were not affected by the number (one or two) of parasitoid eggs per host. The duration of the larval stage was longer and puparia were bigger in parasitoids that emerged from female hosts than those that emerged from male hosts; G. rotundatum was so variable in body size that larger individuals tended to emerge from larger hosts. Though parasitoids did develop even in unfed hosts, such puparia were much smaller in size than puparia developed in fed hosts. The reproductive abilities of the parasitized bugs gradually reduced as the tachinid maggots matured. In parasitized female bugs, ovaries gradually shrank with a suppression of oviposition. Both the number of laid eggs and the percentage of viable eggs decreased rapidly after the 8th day of parasitization. In parasitized male bugs, the fertility rates decreased rapidly after the 8th day of parasitization.
