Determination of drug levels in larvae of Protophormia terraenovae and Calliphora vicina (Diptera : Calliphoridae) reared on rabbit carcasses containing morphine

Two species of blow flies (Diptera: Calliphoridae) were reared on tissues f rom rabbits administered different dosages of morphine. These species, Prot ophormia terraenovae and Calliphora vicina are among the first wave of inse cts colonizing a dead body. Two series of 3 rabbits were given dosages of 1 0, 20, and 40 mg/h of morphine over a 3 h period via ear artery perfusion. A mor phine blood level plateau was attained after 1 h of perfusion. Two ot her rabbits were used as controls. Samples of tissues collected from rabbit s using a coelioscopic technique were determined to have morphine concentra tions similar to those encountered in human overdoses and were correlated w ith dosages of morphine administered. All samples from control rabbits were negative for morphine. Larvae and puparia of both species were regularly c ollected from each rabbit for toxicological analysis. Concentrations of mor phine in larvae reared on rabbit carcasses containing morphine were signifi cantly lower than concentrations found in the tissues. There was a decrease in concentration in morphine observed in transition from feeding 3rd insta r larva to puparium. A correlation between larval concentration and tissue concentration was found only in feeding 3rd instar larvae.