Attack Behavior of Parasetigena silvestris in Relation to Host Density and Behavior

Abstract
The synchrony and interaction of the tachinid parasite, Parasetigena silvestris (Robineau- Desvoidy), with the gypsy moth, Lymantria dispar (L.), were studied in Connecticut in 1973 and 1974. Once in the host habitat the primary method for host location was visual. Each year, the number of P. silvestris attacks (eggs laid) was related directly to the number of large larvae available at any particular time. The number of P. silvestris adults caught on sticky tubes followed the pattern of occurrence of large larvae and attacks. Both the number of larvae attacked (with at least one egg) and the proportion of those with multiple attacks were inversely proportional to the number of large larvae. In 1973, there were ca. 8 times as many larvae, at peak count, as in 1974. The proportion of larvae attacked in 1973 was 17% (N=2237), compared with 54% (N=868) in 1974; in 1973, 14.7% of those attacked had multiple attacks, compared to 48.5% in 1974.s