The influences of the adult age of the parasitoid, host density, instars of host nymphs and host sex on sex allocation of Haplogonatopus apicalis were investigated. The results are as follows : When the mated female parasitoids parasitize the hosts of 3-5, 11-14 and 20-23 days after their emergence, the sex ratio of progeny was influenced by adult age of parasitoids. No significant difference in the sex ratio was recognized under 10, 40 and 100 bunch of host density. The nymphal instar of host affected on the ovipositional frequency and sex ratio of the parasitoid. The highest ovipositional frequency of the parasitoid was realized on the 3rd instar nymphs of the host, and the male ratio of progeny was the lowest on the 3rd instar nymphs. The sex of host affected on the sex ratio of the progeny of the parasitoid. The dryinid wasps parasitized the female hosts were larger than those parasitized the male hosts.

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The genetic mechanism controlling wing-length phenotype in females of the arrhenotokous Thrips nigropilosus was determined by crossing experiments under both short-day and long-day conditions. The geographic variation in the genetic component involved in wing-length phenotype determination was also investigated with seven local population samples. The frequencies of LW-form (long wing) and SW-form (short wing) observed in crossing experiments usually coincided with those predicted from a single pair of alleles with short wing being dominant to long wing. However, in some crosses, the ratio of the two forms did not coincide with the expected one. These results suggested that the wing form is not only governed by a pair of alleles on a single locus but also modified by other factors. A dominant short wing gene was found in Wakkanai and Otoineppu, but not in Abashiri, Asahikawa, Kyoto, Nagasaki and Naha. Based on the results of this and previous studies, we discussed the evolution of wing polymorphism in the female of this thrips.

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The lycaenid, Shijimiaeoides divinus asonis is one of the rarest butterflies in Kyushu, found only in limited areas of Aso. In the Aso area, which includes the world famous Aso volcano, we found that this butterfly inhabits grasslands of 400-800m in altitude. In these grasslands Sophora flavescens, the food plant of this butterfly, grows. These grasslands are burned every spring by farmers and cow-breeders in order to manage them. Our investigation of the influence of this routine grassland-buring upon the population fluctuation of this butterfly indicated the following facts : (1) The population of the butterfly is not decreased in areas where routine grassland-burning occurred. (2) On the other hand, the population of this butterfly decreases markedly in areas where routine grassland-burning has been neglected. However, some of these butterflies appeared to increase when routine grassland-burning was resumed. (3) Routine grassland-burning has a positive influence on the growth of the host plant as well as the nectar plants of this butterfly, e.g., Trifolium repens, Viola mandshurica, Elaeagnus umbellata, Rhododendron kiusianum, Weigela decora, Cirsium sieboldii, Astragalus sinicus and Senecio pierottii. (4) Miscanthus sinensis and other wild tall grasses, which are the dominant species in unburned grasslands, are competitive with these plants, and hence decrease the food and nectar plants essential for the survival of this butterfly. We conclude therefore that routine grassland-burning of this area is necessary in order to maintain this grassland as well as to preserve the population of this rare butterfly.

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