Abstract

The major task of a forensic entomologist is to determine an accurate post-mortem interval (PMI) by analyzing the development or succession of necrophagous insects and other arthropod on the carcass. Blow flies (Diptera: Calliphoridae) are the first arrival at a death scene. A carcass, whether human or animals, goes through a large series of biological, chemical and physical changes as it decomposes from the fresh to the skeletal state. Different stages of this decomposition process are attractive to different species of insects. Flies are attracted to carcasses through volatile compounds emitted during different stages of decomposition. It is therefore probable that flies can easily distinguish between chemical signatures of early and late decay stages. In order to locate the remains, flies are equipped with excellent sensory organs to detect chemical cues being produced by corpse decomposition. For many insects, the chemical senses (olfactory or gustatory) play a major role in decisions regarding feeding, oviposition and other behaviours. Several investigations of chemosensory sensilla in various insect groups have been performed to date, but relatively little information involving forensically important fly species. Due to this deficiency the purpose of this study was to investigate the electrophysiological responses of receptor neurons on the antennae, labium and tarsus of a forensically important blowfly (Calliphora vicina) to different doses of morphine in decomposing tissues as well as odours emitted from the underneath soil. This study reveals that morphine has a repellent effect with significant differences in the degree of sensitivity between different stimulating sites and these conclusions should be considered when estimating PMI or an under estimation will be resulted.

Key words:
Calliphora vicina, Chemoreceptor neurons, PMI