Nabity P D, Higley L G, Heng-Moss T M
Department of Entomology, 202 Plant Industry, University of Nebraska, Lincoln, NE 68583-0816, USA.
J Med Entomol. 2006 Nov;43(6):1276-86. doi: 10.1603/0022-2585(2006)43[1276:EOTODO]2.0.CO;2.
Precise developmental data for forensic indicator blow fly species are essential for accuracy in the estimate of the post-mortem interval (PMI). Why, then, does the determination of the PMI result in conflicting time frames when published conspecific developmental data are used? To answer this question, we conducted constant temperature trials between the developmental minimum temperature and upper threshold temperatures (8-32 degrees C) on the forensically important blow fly species Phormia regina (Meigen) (Diptera: Calliphoridae). Flies were reared using two designs to quantify sources of variation. We measured rearing container temperatures and internal growth chamber temperatures by using thermocouples to accurately record temperatures experienced by larvae and to construct a degree-day model. Differences in experimental design, as seen across temperature studies for this fly species, did not significantly impact larval development. We also found that using set chamber temperatures rather than rearing container temperatures altered the final degree-day model. Using any minimum threshold (including an empirically determined true minimum) other than that from linear interpolation (x-intercept) violated degree-day assumptions and invalidated estimates of the PMI. We observed the minimum developmental temperature to be higher (14 degrees C) than that generated under the x-intercept method (5.46 degrees C) by using data from oviposition to adult emergence. This difference along with the noted difference in accumulated degree-days (using different base temperatures) suggests a need for additional experimentation on other forensically important fly species at low temperature thresholds to help with development of curvilinear models. Former and current estimates of the PMI may be inaccurate if the process to determine the time frame ignored degree-day model assumptions or was based upon questionable data sets.
法医指示性丽蝇物种精确的发育数据对于准确估计死后间隔时间（PMI）至关重要。那么，为什么在使用已发表的同种发育数据时，PMI的确定会产生相互矛盾的时间框架呢？为了回答这个问题，我们在法医重要丽蝇物种黑须亚麻蝇（Phormia regina (Meigen)，双翅目：丽蝇科）上，于发育最低温度和上限温度（8 - 32摄氏度）之间进行了恒温试验。使用两种设计饲养苍蝇以量化变异来源。我们通过使用热电偶测量饲养容器温度和内部生长室温度，以准确记录幼虫经历的温度并构建度日模型。正如在该蝇种的温度研究中所看到的，实验设计的差异对幼虫发育没有显著影响。我们还发现，使用设定的室温度而非饲养容器温度会改变最终的度日模型。使用除线性插值（x轴截距）之外的任何最低阈值（包括根据经验确定的真正最小值）都违反了度日假设，并使PMI估计无效。通过使用从产卵到成虫羽化的数据，我们观察到最低发育温度（14摄氏度）高于x轴截距法得出的温度（5.46摄氏度）。这种差异以及所指出的累积度日差异（使用不同的基础温度）表明，需要在低温阈值下对其他法医重要蝇种进行额外实验，以帮助开发曲线模型。如果确定时间框架的过程忽略了度日模型假设或基于有问题的数据集，那么以前和当前对PMI的估计可能不准确。
