Spatial Variation in Abundance of Forensically Important Entomo-fauna Inhabiting Decomposing Carcass in Minna, Nigeria

Abstract

The influence of study locations and mode of killing on abundance of forensically important insect species informed the present study in Minna, North-central Nigeria. Twenty-four pigs with an average weight of 22.30 kg were sacrificed through stabbing, oxygen deprivation and poisoning with zinc phosphate to determine population dynamics of carcass inhabiting insects during the process of decomposition in two locations (College of Education, COE, and Dutsen Kura, DK) during the dry season in Minna. Five stages of decomposition of cadaver were observed in the study, namely; fresh, bloated, active decay, advanced decay and dry decay stages. Though, eight (8) forensically important insect species (Lucilla sericata, Chrysomya albiceps, C. rufaficies, Musca domestica, Hemipyrellia liqurriens, Sarcophaga carnaria, Hermetia illucens and Ophyra aenacens) were observed colonizing the carcases, pigs sacrificed by poisoning witnessed the presence of only two (2) insect species (L. sericata and M. domestica). A total of 611.70±79.30 insect species were collected throughout the study periods; with stabbed pigs contributing 154.70±21.91 and 152.32±13.83 insects species, respectively, in COE and DK; oxygen-deprived and poisoned pigs contributing 136.62±16.73 and 145.74±17.40, and 12.32±2.83 and 10.00±0.66 insect species, respectively, in COE and DK. There was no significant (p>0.05) variation in the number of forensically important insect species encountered in the study sites, however, there was significant (p<0.05) effect of mode of killing on the numbers encountered. There was also significant (p<0.05) variation in the number of insects collected during each decompositional stage: with active decay stage, consistently, recording the highest number of insect species irrespective of mode of killing. While, M. domestica was, consistently, the most abundant insect species irrespective of mode of killing, decompositional stage and study site, H. illucens was the least abundant. Musca domestica had range of values of 6.00±4.95 (in COE, for poisoned pigs) to 37.76±3.01 insects/ net sweep (in GK, for oxygen-deprived pigs), while H. Illucens had range of values of 4.50±0.71 (in COE, for stabbed pigs) to 5.67±2.36 (in DK, for oxygen-deprived pigs). The study revealed that mode of killing, rather than, study locations had significant effect on abundance of carcass- inhibiting entomo-fauna. The finding of this study will provide baseline information for preparing a forensic template for determining post-mortem interval and cause of human deaths in Minna eco-type settings.