Adaptation to local climatic conditions in the Emma field cricket (Orthoptera: Gryllidae)

A northern (Sapporo) and a southern (Koti) strain of the Emma field cricket (Teleogryllus sp.) were reared for three successive generations in the laboratory, and the characters responsible for the seasonal rhythm of their development were investigated. It was found that the embryonic diapause was obligate in both strains, but that the eggs of the northern strain were able to complete diapause at a lower temperature and also in a much shorter time than were those of the southern strain. The rate of post-diapause embryonic and nymphal development was again more rapid in the northern than in the southern strain. The northern adults tended to be smaller in body size than the southern ones, and this difference seemed to be related to their different rates of development. F 1 hybrids obtained by intercrossing of the second generation adults of the two strains were physiologically, as well as morphologically, intermediate between the parent strains, and it was suggested that the polygenes controlling the rate of nymphal development might be located in the autosomes and X-chromosome. From these results it is concluded that in the Emma field cricket the adaptation of the seasonal rhythm of development to local climatic conditions is genetically controlled. The implication of this variability was discussed to a certain extent