OVIPOSITION PATTERN AND BEHAVIOR OF THE PINE SAWFLY NEODIPRION-SERTIFER (HYMENOPTERA, DIPRIONIDAE)

The potential role of oviposition deterrents in the egglaying behaviou r of Neodiprion sertifer (Geoffroy) females was studied by investigati on of natural egg distribution, and by a laboratory study of potential oviposition deterrents. Pine shoots were sampled from different whorl s on the sun-exposed and the shaded side of trees. More shoots with eg gs from two or more females were found than would be expected if each female laid eggs on a randomly chosen shoot. The anti-predatory larval oral secretion of N. sertifer had no effect on N. sertifer egglaying but acted as an oviposition deterrent to Diprion pini in laboratory ex periments. The different responses may be due to differences in the sp ecies' life-cycles. In other experiments, the effect of the presence o f N. sertifer eggs, extracts obtained from eggs or from needles with e ggs, were all tested on N. sertifer egg laying. None of the treatments had any inhibitory effect on egglaying. Thus, neither the natural pat tern of egg distribution nor the results of the laboratory experiments indicated that an oviposition deterring pheromone is used by N. serti fer. Results from earlier studies, showing a deterrent effect of larva l oral secretion in D. pini, were confirmed.