The effect of flat and undulating terrain on the post-feeding dispersal distance from carcasses of blow fly larvae (Calliphoridae: Lucilia illustris)

Abstract

One method of estimating the post mortem interval (PMI) is to use the oldest stage of immature blow flies on or surrounding a corpse to determine the minimum PMI. When finished feeding, larvae leave a carcass to pupate in the surrounding soil, and can be difficult to find. We investigated if flat and undulating terrain affect how far Lucilia illustris larvae disperse after feeding. We hypothesized that post-feeding larvae disperse over undulating and flat terrain about the same travel distance. However, because larvae must crawl up and downhill in undulating terrain they end up pupating in soil closer to the originating carcass than larvae that crawled over flat terrain. We tested this in a field study using pig half-heads placed on sand which had two surface treatments, flat sand and sand with 2.5 cm undulations. We allowed blow flies to lay eggs on the half-heads, took soil core samples at various distances, then allowed adults to emerge in the lab. In undulating terrain, while more adults emerged from soil cores closer to carcasses than from soil core from flat terrain. However, net travel path lengths were similar for both treatments.