Development of the beetle parasitoids, Brachinus explodens and B. crepitans (Coleoptera: Carabidae)

Abstract

Earlier authors demonstrated that wetland species of the genus Brachinus (Coleoptera: Carabidae) are pupal ectoparasitoids of water beetles of the families Dytiscidae, Gyrinidae and Hydrophilidae. Here we demonstrate that the dryland species, Brachinus explodens and B. crepitans, develop on pupae of ground beetles of the genus Amara (Carabidae). As Brachinus and Amara species often occur together at high densities in crops, the rearing of both Brachinus species was followed in the laboratory. Females laid eggs in the soil and the first instar larva searched for a host. After finding an Amara pupa, a Brachinus larva bit it and then fed on haemolymph exuding from the wound. The second instar larva continued feeding in this way. The third instar larva attached the Amara pupa to its dorsum and ate it completely within c. 2 days. Feeding was followed by a resting phase and moulting to pupa and adult. The total post-embryonic development was completed within 20 days in B. explodens and 24 days in B. crepitans at 24.7 °C.