丝光绿蝇蛹壳颜色变化及其对死后间隔时间推断的意义

【目的】研究不同恒温下丝光绿蝇Lucilia sericata蛹期蛹壳颜色变化，并利用提取的蛹壳RGB值绘制标准色板，为法医学中死后间隔时间(postmortem interval, PMI)的推断提供科学依据。【方法】在16, 20, 24, 28和32℃恒温下分别饲养丝光绿蝇待其发育至蛹期，选取10头蛹为观察样本，每隔12 h定期观察蛹壳的颜色变化，拍照并利用图像分析软件提取蛹期各观察时间点蛹壳颜色的RGB值，再将分析计算后的RGB值还原为标准色板，并采用R软件对蛹发育时间与蛹壳颜色RGB值中的R值的关系进行多元回归分析和拟合。【结果】不同恒温下，丝光绿蝇蛹壳颜色随发育时间均呈现出不均衡的加深趋势，尤其在化蛹初期和临近羽化时变化明显。根据各发育时间的标准RGB值可制作出对应不同恒温的5个丝光绿蝇蛹壳颜色标准色板。【结论】在案发现场，可将检获到的蝇蛹与本研究得到的相近温度下的蛹壳颜色标准色板进行比色鉴定，初步估算蛹期，为死后间隔时间的推断提供科学依据。

Puparium color variation ofLucilia sericata(Diptera: Calliphoridae) and its significance for the estimation of the postmortem interval

【Aim】 This study aims to examine the changing trend of puparium color of a common necrophagous fly (Lucilia sericata) under different constant temperatures and to prepare the standard color plates based on the RGB values of puparium, so as to provide a scientific support for the estimation of the postmortem interval (PMI) in forensic medicine. 【Methods】 Ten pupae of L. sericata were sampled at 12 h intervals from prepupa to emergence under different constant temperatures (16℃, 20℃, 24℃, 28℃ and 32℃). The variation of puparium color at all the observed time points in the pupal stage of L. sericata was observed and photographed. The corresponding RGB values of puparium color were collected and analyzed by digital image processing system to prepare the standard color plates. Multivariate regression analysis was employed for fitting the relationship between the developmental time of pupa and the R value of the RGB values of puparium color by R software. 【Results】 The puparium color of L. sericata gradually deepened with the developmental time under different constant temperatures, and obvious changes were observed at the beginning and final time of the pupal stage. Based on the RGB values at different developmental time, five standard color plates of L. sericata puparium were prepared corresponding to different constant temperatures. 【Conclusion】 At the crime scene, the standard color plates of puparium obtained in this study can be used to preliminarily estimate the pupal stage through visual comparison as an auxiliary method. Based on this estimation, the PMI can be deduced.