Matching Items (4)
- All Subjects: blow flies
- Creators: Weidner, Lauren
- Status: Published
Forensic entomology is the use of insects in legal investigations, and relies heavily upon calculating the time of colonization (TOC) of insects on remains using temperature-dependent growth rates. If a body is exposed to temperatures that exceed an insect’s critical limit, TOC calculations could be severely affected. The determination of critical thermal limits of forensically-relevant insects is crucial, as their presence or absence could alter the overall postmortem interval (PMI) calculation. This study focuses on the larvae of Phormia regina (Meigen) (Diptera: Calliphoridae), a forensically relevant blow fly common across North America. Three populations were examined (Arizona, Colorado, and New Jersey), and five day old larvae were exposed to one of two temperatures, 39℃ or 45℃, for five hours. Across all colonies, the survival rate was lower at 45℃ than 39℃, in both larval and emerged adult stages. The Arizona colony experienced a harsher drop in survival rates at 45℃ than either the Colorado or New Jersey colonies. This research suggests that the range of 39℃ - 45℃ approaches the critical thermal limit for P. regina, but does not yet exhibit a near or complete failure of survivorship that a critical temperature would cause at this duration of time. However, there is opportunity for further studies to examine this critical temperature by investigating other temperatures within the 39℃ - 45℃ range and at longer durations of time in these temperatures.
Blow Flies and the American Diet:Effects of Fat Content on Blow Fly (Diptera: Calliphoridae) Development
Forensic entomology is an important field of forensic science that utilizes insect evidence in criminal investigations. Blow flies (Diptera: Calliphoridae) are among the first colonizers of remains and are therefore frequently used in determining the minimum postmortem interval (mPMI). Blow fly development, however, is influenced by a variety of factors including temperature and feeding substrate type. Unfortunately, dietary fat content remains an understudied factor on the development process, which is problematic given the relatively high rates of obesity in the United States. To study the effects of fat content on blow fly development we investigated the survivorship, adult weight and development of Lucilia sericata (Meigen; Diptera: Calliphoridae) and Phormia regina (Meigen; Diptera: Calliphoridae) on ground beef with a 10%, 20%, or 27% fat content. As fat content increased, survivorship decreased across both species with P. regina being significantly impacted. While P. regina adults were generally larger than L. sericata across all fat levels, only L. sericata demonstrated a significant (P < 0.05) difference in weight by sex. Average total development times for P. regina are comparable to averages published in other literature. Average total development times for L. sericata, however, were nearly 50 hours higher. These findings provide insight on the effect of fat content on blow fly development, a factor that should be considered when estimating a mPMI. By understanding how fat levels affect the survivorship and development of the species studied here, we can begin improving the practice of insect evidence analysis in casework.
The subcategory of evidence deemed trace evidence is frequently seen in crime scenes, and while it is commonly the smallest evidence around, that doesn’t stop it from greatly contributing to the findings at the scene. Blood evidence may be categorized into this group in certain cases at crime scenes, especially in cases of transfer between two objects or people. In this study, the transfer of blood across both porous and non-porous substrates was examined to determine the persistence of blood across both substrates. The resulting stains after each trial of transfers were tested with a presumptive blood test commonly used in crime labs, the Kastle-Meyer test. Throughout all trials of the experiment, it was determined that blood on a non-porous surface typically dries faster as long as there isn’t a pooling effect, which hinders the ability for a stain to be continuously transferred and detected by Kastle-Meyer. Conversely, porous substrates are more likely to absorb and retain the blood in the material, allowing the blood to be released when pressure is applied, causing the stain to transfer more easily and result in a stain that will produce a positive Kastle-Meyer result.
Medicolegal forensic entomology is the study of insects to aid with legal investigations (Gemmellaro, 2017). Insect evidence can be used to provide information such as the post-mortem interval (PMI). Blow flies are especially useful as these insects are primary colonizers, quickly arriving at a corpse (Malainey & Anderson, 2020). The age of blow flies found at a scene is used to calculate the PMI. Blow fly age can be estimated using weather data as these insects are poikilothermic (Okpara, 2018). Morphological analysis also can be used to estimate age; however, it is more difficult with pupal samples as the pupae exterior does not change significantly as development progresses (Bala & Sharma, 2016). Gene regulation analysis can estimate the age of samples. MicroRNAs are short noncoding RNA that regulate gene expression (Cannell et al., 2008). Here, we aim to catalog miRNAs expressed during the development of three forensically relevant blow fly species preserved in several storage conditions. Results demonstrated that various miRNA sequences were differentially expressed across pupation. Expression of miR92b increased during mid pupation, aga-miR-92b expression increased during early pupation, and bantam, miR957, and dana-bantam-RA expression increased during late pupation. These results suggest that microRNA can be used to estimate the age of pupal samples as miRNA expression changes throughout pupation. Future work could develop a statistical model to accurately determine age using miRNA expression patterns.