Insect larval development affects adult traits but the biometric relationships are usually poorly understood, including large odonates. In this study, measurements of morphological traits of larvae, exuviae and adults of Anax imperator were recorded. They were used to investigate the effects of early development on adult morphology. Results showed an increase in larval length during the final instar and the length of its exuviae significantly exceeded that of the larva. Length and body mass of teneral adults were strongly related to the length of their exuviae. Adult males were significantly longer than adult females, while both had the same body mass at emergence. Length of teneral adults was negatively related to the date of emergence in both sexes. During maturation, body mass of males only increased slightly whereas that of females increased greatly. Mature specimens were also significantly longer than teneral individuals. Body mass of mature males and length of mature females were both associated with the date of capture. Wing length did not differ between sexes or from data available from Great Britain. This study underscores the importance of taking into account larval growth in order to better understand the adult traits of odonates.
Two aeshnid dragonflies are described from the Lower Miocene deposits in the Bílina mine in the north of the Czech Republic, including a new genus and species of Anactini, Merlax bohemicus gen. n., sp. n., and a further specimen assigned to the genus Aeshna.
Co-occurrence of species with similar trophic requirements, such as odonates, seems to depend both on them occupying different microhabitats and differing in their life-cycles. The life cycles of the dragonflies Boyeria irene and Onychogomphus uncatus were studied in two consecutive years, mainly by systematic sampling of larvae in seven permanent head courses that constitute the upper basin of the River Águeda, western Spain, in the central part of the ranges of these two species. The size ranges of the last five larval stadia of both species were established based on biometric data. The eggs of the egg-overwintering aeshnid hatched in late spring and early summer and for the gomphid hatching peaked in middle-late summer. Both species showed mixed voltinism with "cohort splitting". B. irene had a dominant three-year development (partivoltinism), with some developing in two years (semivoltinism). O. uncatus requires four, sometimes three years to complete development (all partivoltine). B. irene larvae spent the winter before emergence in the last three, maybe four stadia, as a "summer species". O. uncatus mainly behaved as a "spring species", most larvae spending the last winter in the final larval stadium.