Estimates of the minimum post-mortem interval (mPMI) using the development rate of blow flies (Diptera: Calliphoridae) are common in modern forensic entomology casework. These estimates are based on single species developing in the absence of heterospecific interactions. Yet, in real-world situations, it is not uncommon to have 2 or more blow fly species developing on a body. Species interactions have the potential to change the acceptance of resources as suitable for oviposition, the timing of oviposition, growth rate, size and development time of immature stages, as well as impacting the survival of immature stages to reach adult. This study measured larval development and growth rate of the blow flies Lucilia sericata (Meigen, 1826), Phormia regina (Meigen, 1826) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) over five constant temperatures (15, 20, 25, 30, 35 °C), in the presence of conspecifics or two-species heterospecific assemblages. Temperature and species treatment interacted such that L. sericata larvae gained mass more rapidly when in the presence of P. regina at 20 and 30 °C, however only developed faster at first instar. At later stages, the presence of P. regina slowed development of L. sericata immatures. Development time of C. vicina immatures was not affected by the presence of P. regina, however larvae gained mass more slowly. Development time of P. regina immatures was faster in the presence of either L. sericata or C. vicina until third instar, at which point, the presence of L. sericata was neutral whereas C. vicina negatively impacted development time. Phormia regina larvae gained mass more rapidly in the presence of L. sericata at 20 °C but were negatively impacted at 25 °C by the presence of either L. sericata or C. vicina. The results of this study indicate that metrics such as development time or larval mass used for estimating mPMI with blow flies are impacted by the presence of comingled heterospecific blow fly assemblages. As the effects of heterospecific assemblages are not uniformly positive or negative between stages, temperatures or species combinations, more research into these effects is vital. Until then, caution should be used when estimating mPMI in cases with multiple blow fly species interacting on a body.

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Female blow flies (Diptera: Calliphoridae) demonstrate site preferences when ovipositing on carrion. Preference for oviposition sites is believed to reflect the suitability of the site such that the most preferred locations provide offspring with the greatest chance of survival. A number of factors might influence female choice, including area available for oviposition. For species known to aggregate during oviposition, the surface area of oviposition sites may be a key factor in the decision-making process. Using ImageJ, the surface area or volume of eight common oviposition sites on 13 fetal pig (Sus scrofa domesticus L.) carcasses was measured. Regression analysis was used to determine if body mass could predict the area or volume available for oviposition. We observed significant positive relationships between size of oviposition sites and body mass for all eight oviposition sites. The strongest relationships were observed for the face (R2 = 0.86) and legs (R2 = 0.84). To test the predictive capacity of this relationship, a blind validation study was performed. Five pigs of various body masses were randomly selected, and the available space of the eight sites was estimated using the regression equations. The validation study confirmed that the regression equations for most oviposition sites demonstrated their predictive capacity based on 95% prediction intervals. This research provides a tool that can be used to correct for differences in oviposition site area or volume between carcasses of varying mass so that researchers may gain a greater understanding of the oviposition preferences and aggregation behaviors in future studies.

Research documenting insect colonization of human remains is limited in North America, and currently nonexistent for the American Midwest. Such research is essential for forensic entomologists to identify species of research interest in a region. In this study, we collected insects from human remains in 24 cases across Indiana from June 2016 through September 2018. We analyzed species composition across scene type and season. Eight species of blow flies were collected as larvae from human remains, with Phormia regina and Lucilia sericata as the two predominant colonizers. Phormia regina was the most numerous species collected from outdoor scenes (73.6% of total collections) while L. sericata was the most numerous from the indoor scenes (60.4% of total collections). With scene types pooled, Calliphora vicina and Cochliomya macellaria were the predominant species in the fall (55.6% and 42.2%, respectively); P. regina was the dominant colonizer in the spring (68.6%); and P. regina and L. sericata were the predominant colonizers (46.5% and 44.4%, respectively) in the summer. In addition to these findings, we confirmed the first record of Lucilia cuprina colonizing human remains in Indiana having collected this species from three cases. A single adult Chrysomya megacephala was collected from an indoor scene in southern Indiana, which represents its second collection in the state. Beetles belonging to the families Staphylinidae, Silphidae, Histeridae, Cleridae, Trogidae, Dermestdae, and Nitidulidae were also collected from two outdoor scenes. This study provides important baseline data for forensic entomologists in Indiana, as well as surrounding states with similar environments.