Temperature-dependent development of the blow fly Chrysomya pinguis and its significance in estimating postmortem interval

Chrysomya pinguis (Walker) (Diptera: Calliphoridae) is an endemic Asiatic blow fly species of forensic importance. Chrysomya pinguis is one of the first species to colonize a corpse, especially in high altitude areas during spring and autumn when the ambient temperature is lower. Despite its potential for forensic investigations to estimate the minimum postmortem interval (PMImin), little is known about the development of C. pinguis. In this study, C. pinguis was collected from the Yangtze River Delta region of China and reared at seven constant temperatures between 16 to 34°C to investigate the effect of temperature on development duration, accumulated degree hours and larval body length of C. pinguis. Isomorphen and isomegalen diagrams for C. pinguis were generated using the results, and equations describing the variation in larval body length during development and the temperature-induced variation in development time were also obtained. Chrysomya pinguis can complete its life cycle at 16-34°C. The mean (± SD) developmental durations of C. pinguis from egg to adult at 16, 19, 22, 25, 28, 31 and 34°C were 811.0 ± 3.8, 544.8 ± 2.0, 379.8 ± 1.8, 306.7 ± 2.4, 250.0 ± 2.8, 203.2 ± 2.1 and 185.3 ± 1.6 h, respectively. The mean (± SE) developmental threshold temperature D0 and the thermal summation constant K of the whole developmental process of C. pinguis were estimated as 10.88 ± 0.21°C and 4256.50 ± 104.50 degree hours, respectively. This study provides fundamental development data for the use of C. pinguis to estimate PMImin.

肥躯金蝇（Chrysomya pinguis (Walker)）隶属于双翅目（Diptera）丽蝇科（Calliphoridae），是亚洲特有的具有法医应用价值的丽蝇物种。该物种是最早在尸体上定殖的昆虫类群之一，尤其多见于气温较低的春秋季高海拔区域。尽管其在法医调查中用于推断最小死后间隔时间（minimum postmortem interval, PMImin）的潜力巨大，但目前学界对该蝇的生长发育特性仍知之甚少。本研究以采自中国长江三角洲地区的肥躯金蝇为实验材料，设置16~34℃区间内的7个恒定温度梯度进行饲养，以探究温度对其发育历期、积温小时数及幼虫体长的影响。基于实验结果，我们绘制了该蝇的等发育历期图（isomorphen diagram）与等体长图（isomegalen diagram），并推导得到了描述其幼虫体长随发育进程的变化方程，以及发育时间随温度变化的拟合方程。实验结果表明，肥躯金蝇可在16~34℃温度范围内完成完整生活史。在16、19、22、25、28、31及34℃条件下，该蝇从卵发育至成虫的平均（±标准差）发育历期分别为811.0±3.8、544.8±2.0、379.8±1.8、306.7±2.4、250.0±2.8、203.2±2.1及185.3±1.6小时。本研究估算得到肥躯金蝇整个发育过程的平均（±标准误）发育起点温度D0为10.88±0.21℃，积温常数K为4256.50±104.50积温小时。本研究为利用肥躯金蝇推断最小死后间隔时间提供了基础发育生物学数据。