Effect Of Temperature On The Growth And Development Of The Larvae Of Lucilia Sericata (Diptera: Calliphoridae) And Its Significance In Forensic Medicine

Objective: To clarify the morphology pattern of the larvae of Lucilia sericata and accumulate the basically biological data of the larvae of necrophagous flies for the forensic entomo- logy.Methods: Adult Lucilia sericata were collected from the outdoors. They were reared successively in a biochemical culture box. The experiment was done with the offspring of the third generation. The larvae of Lucilia sericata were reared at temperature ranged from 16℃to 32℃, the humidity, light- period and food supply were kept unchanged.During the entire study, the larvae were removed at 12 hours interval (when studying the larval double age, the larval specimens were removed at 1 hour interval), until 50% of the cohorts had pupated. For measurement and observation, the larvae were killed immediately in 70℃~80℃water and transf- erred to 70% alcohol to use in next steps. Experiment was repeated three times at every temperature.The larval specimens were corroded with 10% KOH for 24 hours and dehydrated with alcohol from 30% to 70% for fifteen minutes. The larvae were thoroughly dehydrated with alcohol from 80% to 100% gradually for half an hour. Finally, the larval specimens were enveloped in Canada balsam after they were made transparent in the dimethylbenzene.The larval specimens were observed under a bin micro- scope, such as the structural traits of cephalopharyngeal sclerite, anterior spiracle, posterior spiracle, the double age larvae. In addition, the length of cephalopharyngeal sclerite, the part of mouth hook, ventral cornua and dorsal cornua, the extent of chitin and the length of posterior spiracle were measured through the JD801 Image Analyze System. Finally, the data were statistically evaluated with Excel.Results: 1 Under the same temperature condition, the length of larval cephalopharyngeal sclerite,the part of mouth hook, ventral cornua and dorsal cornua grew gradually, but the length of each part of the larval cephalopharyngeal sclerite did not change after reaching quickly the maximal length. 2 With the larvae growing, the color of each part of the larvae cephalo- pharyngeal sclerite, anterior spiracle, posterior spiracle became deeper than ever. The extent of chitin strengthened gradually. 3 The speed of larval growth was faster and their maximal length was reached earlier at higher temperature. 4 The double age larvae turned up faster at higher temperature than it did in the lower temperature.Conclusions: The study shows that there are regulars in the development patterns of Lucilia sericata larvae. The age of the larvae can be determined according to the morphology change of the larvae, so the postmortem interval can be determined as long as the investigator counts for the development data of the indicator species.