Analyzing the link between the physiological impact of Paraiotonchium autumnale (Nickle) and spatial distribution of parasitized and un-parasitized Musca autumnalis DeGeer in Northern California fields

Paraiotonchium autumnale (TYLENCHIDA:SPHAERULARIIDAE) are nematode parasites of M. autumnalis (DIPTERA:MUSCIDAE) that occur naturally in cattle pastures in Northern California. The parasites are not uncommon, but seem to have little effect on fly population densities. Understanding how infected and healthy flies are distributed in the field can aid in evaluating the impact of P. autumnale. If infection by P. autumnale reduces flight performance of M. autumnalis in fields, then we would expect parasitized flies to be more patchily distributed than healthy flies. We hypothesize that parasitism by P. autumnale will negatively affect M.autumnalis flight performance, and this cost would make parasitized larvae differently distributed from healthy larvae. Preliminary flight tests measured wing beat frequency and flight duration of infected and healthy flies. Because we cannot determine infection status by observation, flies were dissected upon death and nematode infection was then assessed. Field studies were conducted in Davis, CA and Browns Valley, CA to compare the spatial pattern of parasitized versus healthy flies from dung pats. A handheld Global Positioning System marked the location of collection points as dung pats were collected in transects. Pupae from these pats were individually reared to adulthood. In this work, we ask, essentially, whether this parasite is spatially self-limiting.