Host-chemical orientation in a dipteran soil dwelling larva.

CRESPO. J.E.; LAZZARI, C.R.; CASTELO, M.K.

Tours

Congreso; 26th Annual Meeting of the International Society of Chemical Ecology; 2010

International Society of Chemical Ecology - IRBI

The robber fly Mallophora ruficauda is one of the principal pests of apiculture in the Pampas region of Argentina. As adults they prey on honey bees and other insects, while as larvae they are solitary ectoparasitoids of third-instar scarab beetle larvae. Females of M. ruficauda lay eggs away from the host on tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig and search for their hosts. It is known that second-instar larvae of M. ruficauda exhibit active host searching behaviour towards their preferred hosts, i.e., third instar larva of Cyclocephala signaticollis. Although host-location seems to be mediated by chemical cues, the mechanism of orientation and the sensory organs involved in the location of the host remain unknown. We carried out behavioural experiments in the laboratory to determine which is the main sensory modality involved in the location of the hosts and which are its sensory thresholds of detection. We found that larvae of M. ruficauda detect the chemicals with chemosensilia located in the maxillary palps. However, with only one maxillary palp functional they are still able to orientate to its host. We determined that the larvae of M. ruficauda orientate to their hosts by chemoklinotaxis, as revealed by the fact that the orientation behaviour is lost only when both maxillary palps are ablated. The capability to detect and orientate to odours based on succesive samples are very efficient to a soil-dwelling larvae as M. ruficauda.