Phormia regina (Diptera: Calliphoridae) oviposition behavior on aged substrates.

Blow flies (Diptera: Calliphoridae) arrive to remains and deposit eggs soon after death, making them useful for estimating a minimum postmortem interval. There can be delays in blow fly arrival due to environmental conditions, concealment, or other modifications of the remains. If there is a delay in blow fly arrival, then, the time of colonization and postmortem interval will be different estimates. Field and laboratory studies were conducted to assess how delays in insect accessibility influence blow fly oviposition behavior by allowing small pigs to decompose indoors with insect activity excluded prior to exposing them to blow flies. The aged treatments included were 24-, 48-, 72-, 96-h along with fresh controls. This research assessed oviposition sites, time to oviposition, and number of eggs laid by Phormia regina Meigen in the laboratory. The field component of this research also looked at initial colonizing species of the aged treatments in addition to time to oviposition and oviposition sites. Phormia regina laid the largest number of eggs on the 48-h treatments and had the shortest time to oviposition on the 48- and 72-h treatments. The 48-h treatment also had the greatest number of unique oviposition sites compared to other treatments. The results of this study indicate that P. regina may prefer to colonize aged remains. More research on this topic could clarify how the postmortem interval estimation should be adjusted when there is a delay in insect colonization.