An examination of the effect of household chemicals on blow fly oviposition, growth, development, and estimations of the post mortem interval
This study sought to: (1) observe differences in blow fly activity between fresh and frozen-thawed carcasses, (2) observe the effects of chemicals on the timing of blow fly life events, and (3) observe differences among treatments in blow fly species composition. To answer the first objective, seven pigs, frozen for 2 months and then thawed prior to the experiment, were compared with seven pigs killed shortly before the start of the experiment. No differences in time to the appearance of adult flies, eggs, larvae, or the initiation and conclusion of larval migration were observed between refrigerated only and previously frozen pig carcasses. ^ To study the effects of household chemicals on blow fly life events, a study was conducted in West Lafayette, Indiana, in the summer and fall of 2008, spring, summer and fall of 2009 and the spring of 2010. Seven chemicals were tested: muriatic acid, bleach, lime, Raid® (active ingredient permethrin, tetramethrin, d-cis/trans allethrin), OFF!® (active ingredient N,N-Diethyl-meta-toluamide (DEET)), ammonia and gasoline. Pigs with no chemical treatment served as controls. Significant interactions were found between event and season, season and treatment and event and treatment. Pairwise comparisons found significant differences in the amount of accumulated degree hours for blow fly life events to occur between the control and bleach, muriatic acid, OFF!®, and lime. Pigs treated with Raid® were attractive to adult flies but had no oviposition. ^ Following the methods outlined above, a study was conducted at the Anthropological Research Facility at the University of Tennessee, Knoxville in July-August 2010. Using six human bodies, Raid® and ammonia were tested and untreated bodies served as controls. Bodies treated with Raid® had between a 1,000–3,000 accumulated degree hour (ADH) delay in insect activity when compared to controls and ammonia, depending on the insect life event. The application of chemicals can significantly impact a forensic entomologist's estimation of the postmortem interval and the data obtained from this research will help yield more accurate assessments.^
Ralph E. Williams, Purdue University.