Forensically important blow flies exhibit no nocturnal activity under LED streetlights.

Medicolegal forensic entomology relies largely on blow fly (Diptera: Calliphoridae) activity to estimate a minimum postmortem interval (mPMI). The prevailing assumption, that blow flies are inactive at night, leads to the exclusion of nocturnal colonization from mPMI estimates. Artificial light at night (ALAN), however, especially from the increasing use of light emitting diode (LED) streetlights, may alter this innate behavior. Baited traps were deployed at two sites: one natural site that was dark at night (unlit) and one undeveloped but with infrastructure site that was LED-illuminated at night (lit). Samples were collected during daytime and nighttime periods. A total of 1,544 blow flies representing seven species were collected. Only six flies (0.4% of the total) were captured at night, four in unlit and two in lit environments, indicating minimal nighttime activity. These results suggest that, under current conditions, ALAN is unlikely to induce nocturnal blow fly behavior and impact mPMI estimations. Further research across diverse taxa and environments is needed to better understand the effects of ALAN on insects of forensic importance.