Development of blow flies with insecticide exposure

Blow flies (Diptera: Calliphoridae) are forensically relevant insects associated with decomposition. Females detect remains and oviposit shortly after detection and the resulting larvae develop on and around the decomposing remains. Previous research suggests that chemicals, including insecticides, can change blow fly behaviors (e.g., arrival, and oviposition) as well as larval development. Forensic entomologists need to understand how insecticides can affect these behaviors when estimating a time of colonization (TOC)—or time since egg-laying on remains. This study examined the effects of two frequently used insecticides: bifenthrin (pyrethroid) and clothianidin (neonicotinoid) on blow fly development. There may be delays in develop and decrease in size at higher insecticide concentrations. Experiments were conducted using two of the most common blow fly species in the United States—Lucilia sericata (Meigen) and Phormia regina (Meigen). Gravid females were provided with liver to promote oviposition. Eggs were transferred to liver pieces treated at different concentrations and placed in mason jars for rearing. The concentrations for bifenthrin were 7351.90 ppm, 735.19 ppm, and 73.51 ppm; and for clothianidin were 299. 56 ppm, 29.95 ppm, and 2.99 ppm for high, medium, and low, respectively. Three larvae were removed every 24 h to measure larval length and instar duration. Pupariation rate, stage duration, adult emergence rate, adult size, and sex ratios were recorded. These results will be crucial to understanding the changes in development and subsequent TOC estimations caused by the presence of insecticides.