DIAPAUSE INITIATION AND PUPATION SITE SELECTION OF THE BRACONID PARASITOID MICROPLITIS-MEDIATOR (HALIDAY) - A CASE OF MANIPULATION OF HOST BEHAVIOR

Microplitis mediator (Haliday), a braconid parasitoid reared on the be rtha armyworm, Mamestra configurata (Walker), entered diapause at 16-d egrees-C and a 12L:12D (100%) or 14L:10D photoperiod (99%) but not at 16-degrees-C or 21-degrees-C under a 16L:8D photoperiod or at 21-degre es-C and a 12L:12D photoperiod. Diapause development was accelerated b y cold treatment; adults emerged from diapause more rapidly with incre asing duration of cold exposure at least up to 120 days. The main pupa tion site was found to be on senescent canola leaves which formed a le af litter on or near the plants. Nearly all unparasitized fourth-insta r hosts (98-100%) were found on host plants, whether the conditions in duced diapause or not. Only 16-23 and 0% of parasitoids pupated on hos t plants under conditions of non-diapause or diapause induction, respe ctively. Because the pupation site of the parasitoid depends on moveme nt of the host, these results suggest that mature parasitoid larvae mo dify movement of their host.