Sex ratio; Odonata; dragonflies; Gomphidae; proandry; environmental impact

At emergence (the final instar, F-0) a strong bias for females was observed within local populations of Gomphus flavipes (Charpentier), Gomphus vulgatissimus (Linné) and Ophiogomphus cecilia (Fourcroy) (Anisoptera: Gomphidae). Males represented 45.6% of all specimens (43.5% in the first and 46.4% in the second research year). The results of the ?2 test supported the female-biased sex ratio in populations of all three species. The sex ratio in populations varied significantly in time during the emergence season, caused by the fact that all three species demonstrated a significant protandric trend. The greatest changes in sex ratio during the emergence season were demonstrated by G. flavipes (coefficient value -0.007542); the smallest were recorded in G. vulgatissimus (CV -0.008617). Environmental impact did not prove to act be a factor which has an effect on the sex ratio of species with phenotypical determination of sex.

At emergence (the final instar, F-0) a strong bias for females was observed within local populations of Gomphus flavipes (Charpentier), Gomphus vulgatissimus (Linné) and Ophiogomphus cecilia (Fourcroy) (Anisoptera: Gomphidae). Males represented 45.6% of all specimens (43.5% in the first and 46.4% in the second research year). The results of the ?2 test supported the female-biased sex ratio in populations of all three species. The sex ratio in populations varied significantly in time during the emergence season, caused by the fact that all three species demonstrated a significant protandric trend. The greatest changes in sex ratio during the emergence season were demonstrated by G. flavipes (coefficient value -0.007542); the smallest were recorded in G. vulgatissimus (CV -0.008617). Environmental impact did not prove to act be a factor which has an effect on the sex ratio of species with phenotypical determination of sex.