SD40: Blow fly oviposition behavior on aged substrates

Blow flies (Diptera: Calliphoridae) are useful in death investigations as they arrive to remains and deposit eggs quickly after death, which makes them beneficial for establishing a minimum postmortem interval. Previous research has demonstrated that blow flies lay more eggs on aged (more decomposed) tissue compared to fresh. However, these studies are mostly completed in a laboratory or have used other animal carcasses as models for human decomposition.



A field experiment was conducted to assess the influence of aged substrate on blow fly arrival, colonization, oviposition site selection. Small pig carcasses were aged indoors with insects excluded for 24, 48, 72, and 96 hours. All carcasses were documented with photographs and insect samples were collected from each replicate after 1 hour. All 10 pigs were colonized within the first hour, however, this study demonstrated differences in the diversity and oviposition site selection among the aged carcass treatments.



Laboratory experiments were conducted using Phormia regina (Meigen) and Lucilia sericata (Meigen) to assess number of eggs laid, colonization, and oviposition site. Pig carcasses were aged in the same manner as the field experiment before introducing them to insect cages containing 20 gravid females and 10 males. The pigs were photographed and examined hourly and after all pigs were colonized, eggs were removed for counting. This experiment showed differences in number of eggs laid, time of colonization, and oviposition site selection. These results can provide insight for investigations with a delay in insect access to the remains to strengthen minimum postmortem interval estimates.