The significance of the diversity in age composition of Calathus melanocephalus L. (Col., Carabidae) in space and time at Schiermonnikoog

Abstract

Calathus melanocephalus L. reproduces at Schiermonnikoog in July, August and September. From literature it is known, that in some areas this species reproduces in August, September and October or still later.The population at Schiermonnikoog is composed of individuals of an old generation (adult overwintered beetles) which reproduce especially in July and in the first part of August and of individuals of a new generation (overwintered in the larval stage and hatched in June or July) which reproduce especially in the second part of August and in September.Both the differences in space and time in this age composition and those in fecundity are described.It is discussed, to what extent the differences in time of reproduction of populations in different localities in the same geographical area and of populations in different geographical areas, may be explained by the possible differences in age composition. In this context, differences between larval overwintering and adult overwintering species are discussed.The fecundity of the old females has been shown to be smaller than that of young females; moreover, the fecundity of individuals of both the old and new generation is different in the populations in the three localities studied.There is also pointed to the relation between age composition and the fecundity, with regard to the length of the reproductive period.Finally, the significance of the differences in space and time in age composition and fecundity to the chance of survival of Calathus melanocephalus in different areas is discussed.