Abstract
Larvae of gypsy moth were placed on trees in forests and the foraging behavior of P. jadwigae was observed. The wasp showed aggregative response to the prey populations. When there were 50 or more larvae in the study plots, the number of the wasps foraging in the plot increased linearly day by day, and all of them succeeded in capturing larvae. The number of larvae disappearing in a day showed linear relationship with the number of wasps seen in a 15min period at the same place. Most of the wasps shuttled between their nests and the foraging site and spent about 21 min in capturing a larva and feeding their own larvae. When fewer larvae were placed, not all the wasps succeeded in capturing a larva, and the time spent for foraging was about 1.2 times longer. One hundred larvae which were placed at 17 plots in four forests showed a very high mortality rate in a 10 day period. Polistes wasps seemed to have foraged for the larvae at 16 of the 17 plots or sub-plots.
