An investigation ofCaligula japonica(Lepidoptera: Saturniidae) egg distribution and associated parasitoids on walnut trees (Juglans regiaL.) in northwestern China

Caligula japonicais a serious defoliator pest of walnut trees,Juglans regia, in China. Important information about the occurrence ofC. japonicaegg masses on host plants and their indigenous parasitoids under field conditions are rarely documented. Here the distribution of egg masses ofC. japonicaon the trunks ofJ. regiaand occurrence of its parasitoids in Kangxian, the most important walnut production area in northwestern China, were investigated. The results revealed that the egg masses were mainly located at 109.2 +/- 62.3 cm height. The number of egg masses exhibited a significant positive linear relationship with the diameter of trees and a parabolic relationship with host tree height. The natural parasitism rate showed a significant negative linear relationship with the size of egg masses but no relationship with the height of egg masses. The percentage of parasitized egg masses and parasitism percentage of eggs were 49.0% and 7.0%, respectively. We found seven egg parasitoid species belonging to three genera, in whichMesocomys trabalaehad the largest Berger-Parker index (0.6963). In addition, the coparasitism ofM. trabalaeandM. albitarsisaccounted for 39.7% of the total coparasitized egg masses. This investigation provides basic information for utilizing egg parasitoids againstC. japonicain the future.