The temperature dependent development rates of blow flies allow blow flies to be used as biological clocks in forensic death investigations. However, the upper thermal limits of adult survival and oviposition, both required for producing larvae, remains largely unknown. Therefore, in this study we examined the impact of a range of temperatures between 37 °C and 44 °C on the likelihood of survival and egg-laying behavior of two species of medicolegal forensic importance, Lucilia sericata (Meigen) and Phormia regina (Meigen) (Diptera: Calliphoridae). To quantify the upper temperature limits of survival, adult fly colonies were exposed to 37 °C, 41 °C, 42 °C, 43 °C, and 44 °C for 24 h. Similarly for oviposition trials, adults of both species were exposed to 40 °C, 42 °C, and 43 °C with P. regina oviposition also observed at 41 °C. Trials lasted for 24 h with oviposition substrate replenished at the 12 h mark. A yes/no determination on egg deposition was made, eggs were counted, and a yes/no determination was made on egg hatch. Survival did not differ by species (p = 0.096). Overall, survival decreased with increasing temperatures, with ~100% at 37 °C, ~50% at 41 °C, ~37% at 42 °C, ~15% at 43 °C and 0% at 44 °C. Lucilia sericata laid eggs capable of hatch up to 43 °C, while Phormia regina egg-hatch was observed up to 41 °C. These results indicate a greater thermal tolerance of adult survival than for egg deposition and successful egg hatch, which supports previous experiments indicating blow flies stop laying eggs at sub-lethal temperatures. Furthermore, these data indicate that adult blow flies may find remains at or near time of death but may delay egg deposition until temperatures drop below an acceptable threshold.

Understanding the biodiversity and distribution of forensically relevant blowflies (Diptera: Calliphoridae) in a region can aid in legal investigations when insects are associated with remains. For this purpose, we conducted a 14-month-long blowfly survey at the Anthropology Research Facility (ARF) of the University of Tennessee in Knoxville, Tennessee. Traps baited with pork kidney were deployed for 24 h twice a month throughout the study. A total of 3180 adult blowflies were collected, comprising 13 species from 7 genera. Phormia regina (Meigen) and Lucilia coeruleiviridis (Macquart) were the predominant species collected from this survey, with collections representing 65.9% and 20.6%of total flies captured, respectively. In addition to relative abundance, we investigated blowfly community composition, species abundance, richness, and diversity by season. One state record was identified, with adult Protophormia terraenovae (Robineau-Desvoidy) being collected for the first time in Tennessee. Additionally, an earlier record of Chrysomya megacephala (Fabricius) in Tennessee was noted. These findings can be used to aid in legal investigations in the area and surrounding areas where work is limited, as well as to provide information on which forensically relevant species should be the subject of future research in the area.

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 frequently used in determining the minimum postmortem interval (mPMI). Blow fly development is influenced by a variety of factors including temperature and feeding substrate. Unfortunately, dietary fat content remains an understudied factor in the development process, which is problematic given the high rates of obesity in the United States. To study the effects of fat content on blow flies we investigated survivorship, adult weight, and development time (overall and by sex) of Lucilia sericata (Meigen) and Phormia regina (Meigen) on ground beef with 10%, 20%, or 27% fat. As fat content increased, survivorship decreased across both species with significant impact to P. regina. 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. Overall development times did not vary by fat content, excluding 27% for P. regina. Additionally, development times did not vary by sex for P. regina but did differ (P < 0.05) for L. sericata with females taking longer to develop. These findings provide insight into the effect of fat content on blow fly development, a factor that should be considered when estimating an 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.

Utilizing insects in legal investigations as a tool for estimating forensically important timelines (e.g., minimum post-mortem interval (min-PMI)) is becoming more commonly used and accepted throughout the world. In the United States much of the climate is temperate, however, the Sonoran Desert is an arid location with extreme heat and irregular rainfall. Work on forensically relevant insects in this region is severely understudied. This study surveyed the populations of forensically important blow flies (Diptera: Calliphoridae) in Phoenix, Arizona for one year using traps baited with four different food sources. Nine species across four genera were collected with Lucilia sericata, Calliphora latifrons, and Lucilia mexicana accounting for 98.6% of total blow flies captured in the baited traps. Abundance drastically changed throughout the year, ranging from 500+ flies to 0 flies captured in a month, with species abundance correlating with temperature and humidity. These results reveal that environmental conditions (i.e., maximum temperature and relative humidity) may limit blow fly activity or seasonally remove (or make inactive) entire local populations, thus affecting their ability to colonize remains and produce an accurate min-PMI.

A geometric morphometric analysis was performed on the right wing of adult Calliphora vicina (Robineau-Desvoidy) collected across 4 altitudinal levels in Sicily. The objective of this study was to assess differences in shape and centroid size (CS) between females and males and across elevations. The wings analyzed in this study were removed from adults of C. vicina collected with baited traps at 20, 700, 1,153, and 1,552; for this study, 19 landmarks were identified in each wing. The coordinates of the landmarks were aligned and superimposed to prevent variations due to position, orientation, and scale; they were then scaled to the same CS and recentered. CS and Procrustes differences were, respectively, used to assess variations in size and shape. Significant differences were observed in wing shape between males and females but not between all altitudinal levels. Female wings were found to be significantly larger than males (P < 0.01). Wings of flies collected at the highest altitudinal level resulted in significantly larger wings than those collected at lower altitudes (P < 0.001), with CS values ranging from 12.1 to 14.1. Variation in wing shape can impact thermal regulation, and therefore, oxygen content, temperature, atmospheric pressure, and solar radiation can have an effect on an insect’s body and activity levels. At high elevations and lower temperatures, larger wings could mean less energy expenditure when flying to increase body temperature.