Artificial trap-nests in Ukraine

[Euchroeus]

The biological features of Chrysura laevigata (Abeille, 1879) (Hymenoptera, Chrysididae) at the steppe
zone of Eastern Ukraine by K.V. Martynova [in Russian]

Abstract:
The results of using the method of artificial trap-nests on the territory of reserve “Kam’yani mohyly” (department of Ukrainian Steppe Reserve) in 2008–2010 are presented. For the first time the chrysisid wasp Chrysura laevigata was shown to be the host of megachilid bee Osmia coerulescens and the sex ratio of the former was shown to be 2:1 (133♀: 66 ♂). The role of Ch. laevigata in the regulation of host’s abundance is detected – it is the main enemy of O. coerulescens. The regularity of occupation of the host nests and the biotopical preference within the reserve are also discussed: the highest abundance of the bee and its enemy is registered at the mesophytic biotops, where the chrysidid wasps invade approximately the half of host nests. Both Ch. laevigata and O. coerulescens were shown to overwinter as imagoes (enclosed in their cocoons). One more enemy, the inquiline Sapyga quinquepunctata L. (Sapygidae), was revealed in the nests of O. coerulescens – occupied 10% of host nests, and the half of them it shared with Ch. laevigata. The both enemies had been developing successfully, while following different strategies: the inquiline S. quinquepunctata fed on pollen mass, the methaparasite Ch. laevigata, obviously, ate the last instar larva/prepupae of host bee. The main reason to state the latter is the fact that all cocoons of chrysidid wasp were found within the cocoons of the host bee (the «hidden cocoons»). The investigation on cocoons structure gave also the opportunity to reveal some aspects of interaction between Ch. laevigata and O. coerulescens at the preimaginal stages.