Mating and activity of gonads in pre-dormant and dormant ladybirds (Coleoptera: Coccinellidae)

Abstract

Summary We checked voltinism tendencies in four ladybird species considered to be univoltine in Central Europe. The developmental state of male and female gonads and the incidence of mating females were investigated between September 1998 and April 1999 in ladybirds sampled from two localities in the Czech Republic: (1) in the vicinity of the town of Ceske Budejovice (S Bohemia) and (2) at the top of the hill Raná (N Bohemia). Interspecific differences in those aspects of reproductive activity were checked in the pre-dormancy/early dormancy period (September) in Ceratomegilla undecimnotata (Schneid.), Coccinella septempunctata L., C. quinquepunctata L. and C. magnified Redtb. Changes in the course of dormancy were monitored in C. undecimnotata and C. septempunctata. Since C. septempunctata from S Bohemia was relatively heavily parasitized by a braconid, Dinocampus coccinellae (Schrank), the effect of parasitization by this parasitoid on ladybird sexual activity was also analysed. In September, all C. undecimnotata females had completely inactive ovaries, and none of them had mated, while some females of Coccinella spp. displayed a certain degree of ovarian activity and many females had mated. The activity of testes varied greatly in all species, but the least active, on average, was C. undecimnotata. In both C. undecimnotata and C. septempunctata males, the mean activity of the testes considerably decreased between September and January and then increased in April. However, at each date it was significantly lower in C. undecimnotata than in C. septempunctata. The ovaries of some C. septempunctata females started to mature already in April, while all C. undecimnotata females still had inactive ovaries. C. septempunctata females parasitized by D. coccinellae were more often mated and more often snowed certain activity of ovaries than unparasitized ones. In males, however, parasitization caused reduction in the activity of gonads. It can be concluded that the entire central European population of C. undecimnotata is probably obligatorily univoltine, while in populations of the three Coccinella species some individuals are potentially multivoltine. Diapause and post-diapause development is modified, at least in C. septempunctata, due to parasitization by D. coccinellae.