Keywords

forensic entomology, insect seasonality, environment, evaporation

Research Abstract

Minimum postmortem interval (mPMI) estimations are critical to solving cases of equivocal death and the accuracy of these predictions can depend on the understanding of necrophagous fly successional patterns. In order to better understand the successional patterns of necrophagous flies, it is important to know the seasonality of forensically relevant fly species—that is, the baseline pattern of their presence and absence in relation to annually cyclic environmental factors. Since many environmental factors play a role in insect seasonality, it is possible that some of these factors can be summed to create an index that represents seasonality in a simpler form. This study seeks to determine whether or not temporal variations in the presence of particular fly species are directly related to changes in environmental conditions. Minimum and maximum temperature, solar radiation, wind speed, and humidity were the environmental factors of interest in this study and have been shown in previous studies to affect carrion fly assemblage. Specimens were passively collected in Northwestern Indiana using a fly trap with rotting chicken bait as an attractant, then pinned and morphologically identified. The presence and relative abundances of relevant fly species were compared to local environmental factor data to determine whether seasonality exists for carrion flies based predominantly on evaporative index or on other environmental variables. Data collected in the summer of 2015 shows that Dipteran community composition varies temporally within the summer season. The differences in relative species abundance and species presence throughout the sampling period can likely be attributed to environmental changes. However, the environmental variables exerting the greatest effects on fly presence and abundance are as of yet unidentified by this study. Because of this shortcoming, the work done this summer represents only a part of a multi-year project in attempting to identify any relationship between fly presence and environmental conditions.

Session Track

Food, Soil, Plant and Animal Science

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Aug 6th, 12:00 AM

Seasonality of Forensically Relevant Diptera in Northwestern Indiana

Minimum postmortem interval (mPMI) estimations are critical to solving cases of equivocal death and the accuracy of these predictions can depend on the understanding of necrophagous fly successional patterns. In order to better understand the successional patterns of necrophagous flies, it is important to know the seasonality of forensically relevant fly species—that is, the baseline pattern of their presence and absence in relation to annually cyclic environmental factors. Since many environmental factors play a role in insect seasonality, it is possible that some of these factors can be summed to create an index that represents seasonality in a simpler form. This study seeks to determine whether or not temporal variations in the presence of particular fly species are directly related to changes in environmental conditions. Minimum and maximum temperature, solar radiation, wind speed, and humidity were the environmental factors of interest in this study and have been shown in previous studies to affect carrion fly assemblage. Specimens were passively collected in Northwestern Indiana using a fly trap with rotting chicken bait as an attractant, then pinned and morphologically identified. The presence and relative abundances of relevant fly species were compared to local environmental factor data to determine whether seasonality exists for carrion flies based predominantly on evaporative index or on other environmental variables. Data collected in the summer of 2015 shows that Dipteran community composition varies temporally within the summer season. The differences in relative species abundance and species presence throughout the sampling period can likely be attributed to environmental changes. However, the environmental variables exerting the greatest effects on fly presence and abundance are as of yet unidentified by this study. Because of this shortcoming, the work done this summer represents only a part of a multi-year project in attempting to identify any relationship between fly presence and environmental conditions.