Further observations on the nocturnal oviposition behaviour of blow flies (Diptera: Calliphoridae).

Calculating the age of immature stages of blow flies showing the longest period of association with a dead body often gives a fairly accurate estimate of the post-mortem interval (PMI). Determination of the exact time of oviposition by these flies had generally been made in the light of the conventional belief that blow flies are neither active nor do they lay eggs during night. This method of estimating the time of oviposition was modified when Greenberg [J. Med. Entomol. 27 (1990) 807] reported nocturnal oviposition by three calliphorid species that are occasionally used as forensic indicators. However, a technical problem with his experiment, having long term consequences, was placement of the bait on the ground among bushes. This could have made it possible for the flies already resting near the bait to climb over the piece of meat and lay eggs. Though Greenberg's experiment proves beyond any doubt that blow flies do lay eggs at night as well as by day, active attraction of these flies at night towards the oviposition medium had yet to be proved and the present experiment has been designed for this purpose.