Attraction of the sheep blowfly, Lucilia sericata (Diptera : Calliphoridae) to carrion bait in the field

The facultative ectoparasite, Lucilia sericata (Meigen) has been described as a pioneer colonizer of carrion. This behaviour is believed to enable it to escape the intense interspecific competition which can occur between dip terous larvae within carrion. Such escape is necessary as this fly species has been thought to have reduced competitive ability, resulting from its ev olutionary progression towards parasitism. In the work reported here, the a ttraction of L. sericata to carrion bait at different stages of decompositi on (fresh to 28 days old) was investigated in the field. Trials were run ov er three years, with carrion bait presented in the presence and absence of sodium sulphide. Decomposition had a significant effect on the numbers of L . sericata caught; more decomposed bait caught greater numbers of L, serica ta than fresh bait. However, this effect was not apparent if sodium sulphid e was added to the carrion. With sodium sulphide added, there was no signif icant difference in the attraction of female L. sericata, regardless of bai t age. There was no general relationship between carrion bait age and the n umber of female L. sericata caught in different stages of ovarian developme nt. The present data, therefore, suggest that L. sericata does not act excl usively as a pioneer species. Furthermore, this work suggests that, if used with sodium sulphide, the stage of carrion bait decomposition does not sig nificantly modify carrion bait attractiveness.