PRELIMINARY STUDY ON THE LIFE HISTORY OF THE LARCH CATERPILLAR DENDROLIMUS SIBIRICUS TSCHETW. (LEPIDOPTERA, LASIOCAMPIDAE)

1. In China, the larch caterpillar, Dendrolimus sibiricus Tschetw. is mainlydistributed in Hei-lung-kiang, Chi-ling, Liao-ning Provinces and Inner Mongolia.It attacks many species of pines and especially prefers Larix olgensis which issometimes severely injured. 2. It occurs one generation each year or each two years. The larval stagevaries from 7 to 9 instars, however, the larva of one generation per year possesses7 instars. The 3rd and 4th instars or the 6th and 7th instar larvae hibernate inwinter. Adults emerge in the next July and August. 3. The hibernating larvae come down from the pine tree and hide themselvesunder debris above the ground. In the next spring, when the average temperaturereaches above 10℃. the larvae become active and climb up the tree trunk. Mostcocoons are formed at the tree cap, but a few scattered on the tree trunk or onother shrubs. 4. The female mates once only in her life. The oviposition period of matedfemale lasts 1 to 10 days and generally 7 days. While the unmated female mayreach 13 days. The average number of eggs is as high as 312, and nearly 60% ofthe eggs are laid in the night shortly sfter copulation takes place. The longevityof the adult has been counted about 9 days in average, but the unfertilized femalemay live 13 days. 5. Many species of natural enemies are found: Telemonus dendrolimusi Chu Oencyrtus dendrolimusi Chu are mainly the egg parasites; Apanteles eucosmaeWilkinson, Apanteles ordinarius (Ratz.), Campoplex proximus Forster Rhogas spec-tabilis (Mats.) are parasitic on the larvae. Beside, several parasitic flies are foundfrom the pupae and the species need to be determined.