Cuticular muscle attachment sites as a tool for species determination in blowfly larvae

First results of a new method for species determination in third instar larvae of saprophagous blowflies are introduced. Cuticular attachment sites of a limited number of transversal muscles are visualized for light microscopic analysis. After removing the muscles and staining the cuticle, the attachment sites become visible as laterally symmetrical segmental clusters of dark dots. The combined patterns of five such clusters, located in the second, third and fourth segments, show sufficient differences to allow reliable separation of externally very similar larval Lucilia sericata and Lucilia illustris as well as Calliphora vomitoria and Calliphora vicina, the most common saprophagous blowfly species in Europe. Species determination even in poorly conserved, discoloured and fragmented blowfly larvae becomes possible with this new method. The method can primarily be applied for postmortem interval (PMI) calculations in forensic entomology. Interspecific morphological similarity of the larvae and differences in growth rate make species determination an essential requisite for an exact PMI calculation.