Seasonal Variation in the Adult Size of Pachydiplax Longipennis (Burmeister) (Odonata, Libellulidae)1

Abstract

For several years it has been apparent that adults of Pachydiplax longipennis (Burmeister) normally exhibit a considerable range in size throughout their eight month flying season in the Gulf coast area. The extent of these variations and the reasons for them have remained unknown. A search of the literature indicates that other entomologists have noted the same phenomenon. Calvert (1893, 1901—08), Kellicott (1890), and Wright (1937) all called attention to this great size variation in Pachydiplax adults, and Wright (1943) attempted to base the reasons for it in the Gulf coastal marshes on either “the effect of the saline variation upon the nymphs or to a variation in food abundance.”