Gregariousness and Development of Larvae of the Pine Needle Gall Midge, Thecodiplosis japonensis UCHIDA et INOUYE (Diptera : Cecidomyiidae), in a Gall

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The gregariousness and the competition for food among larvae of the pine needle gall midge, Thecodiplosis japonensis UCHIDA et INOUYE, were studied during the period from 1976 to 1982. The competition in the galls was not so strong as to cause the death of larvae, but it did decrease larval body size. This decline in the size of larvae might lead to increased mortality of the overwintering population in the soil and to a decrease in body size and fecundity of females; but the competition is unlikely to be important in regulating the population density. The gregariousness of larvae seemed to give them a greater chance to settle themselves and to survive in the gall. Galls with more larvae seemed to produce more females per gall, which resulted in higher fecundity per gall and per population.