Diurnal Oviposition of Blow Flies

Abstract

Blow flies (Diptera: Calliphoridae) are usually the first insects to oviposit (lay eggs) on carrion. The timing of blow fly oviposition is critical for determining a postmortem interval (PMI) estimation, which is the time that has passed between death and corpse discovery. The objective of this investigation was to gain more information about the timing of blow fly oviposition so that a more accurate PMI could be calculated. Past research in our lab has shown that blow fly oviposition occurs an average of 4.75 hours after sunrise. This year’s research expanded on previous studies by placing three piglets in a remote, wooded area one hour after sunrise. The piglets were checked once an hour until oviposition occurred, and it was recorded whether flies and eggs were present each hour. Egg masses were collected. DNA analysis and BLAST were used to identify the individual blow fly species. The timing of oviposition, in hours after sunrise, was analyzed with respect to temperature, humidity, and light intensity. The research was repeated six times in the fall of 2016. Flies were first seen an average of 2.3 hours after sunrise, and oviposition was observed an average of 4.16 hours after sunrise. The average lux reading at the time of oviposition was 26,755 lux, but ranged between 5,790-52,300 lux. This research has importance in both the scientific and forensic communities, as a more accurate PMI can assist with the validity of a forensic investigation