Relations between free-living nematodes and dung-burying Geotrupes spp.(Coleoptera: Geotrupini)

The nematode fauna of more than 300 brood balls of the beetle species Geotrupes spiniger and G. vernalis was determined. In this context the insect biology was srudied, also. The succession of nematodes in nine G. spiniger brood balls and six G. vernalis brood balls was observed in the course of the entire individual development of the beetles. The results show that Diplogaster hirschmannae, D. henrichae and D. labiomorphus are nematodes which have specialised in phoresy on Geotrupes beetles. Experiments on the generation lime and number of offspring of these three diplogasterids show adaptations of the reproduction strategies to life in the brood ball. The nematodes are in a position to live on the limited resources of food until the young beetle pupates. Only then many second-stage juveniles develop into dauer larvae. The dauer larvae seek shelter in the genital region of the newly hatched beetle. There they stay until their carrier has started to build a brood burrow.