Relative Roles of Blow Flies (Diptera: Calliphoridae) and Invasive Fire Ants (Hymenoptera: Formicidae: Solenopsis spp.) in Carrion Decomposition.

Fire ants (Solenopsis spp.) have increasingly been reported from carrion in the southeastern United States and are now a part of the normal succession community. There have been previous observations of these ants altering carrion and preying on other carrion-attendant fauna; however, the overall effects of these activities on carrion decomposition rates, community composition, and blow fly larval development are poorly understood. Alteration of these ecological processes by fire ants could affect the forensic interpretation of entomological data. We conducted a study in Mississippi and Florida whereby portions of the succession fauna were excluded from access to pig carrion to study the relative effects of fire ants and blow flies on carrion decomposition and succession: a control with all fauna having access, a second treatment where fire ants and other geophilic taxa were excluded, and a third treatment in which blow flies and other large organisms were excluded. Fire ants inflicted lesions in the carrion, buried portions that touched the ground, and preyed on some members of the succession fauna. Their exclusion did not affect carrion decomposition rates that were measured but slightly affected the overall carrion community, and strongly affected the oviposition and development of blow flies. Despite the presence of fire ants early in the control, blow flies were eventually able to overcome predation of eggs and larvae, continue colonization, and complete development; however, the delay in the colonization of blow flies on carrion could affect the determination of postmortem intervals when development rates of blow flies are considered in the calculation.

Field study on the attraction and development of insects on human meconium and breast-fed-infant feces.

Urogenital myiasis of newborn infants, although rare, is usually considered to indicate neglect due to attraction of flies to feces; however, infant feces have not been determined to attract insects. Human meconium and breast-fed-infant feces were used to determine attractiveness to insects and to examine subsequent colonization and growth patterns of insect larvae. Despite small amounts of fecal material present, adults of Lucilia sericata arrived at breast-fed-infant feces within five minutes; insects were rarely observed on meconium. Oviposition and growth of L. sericata larvae occurred only on breast-fed-infant feces; however, the larvae did not progress beyond the second instar. These data suggest that urogenital myiasis by L. sericata in newborn human infants within the first few days postpartum would not be expected, but desiccation and depletion of infested feces may provide a possible pathway for urogenital myiasis in older newborn infants.

Effect of investigator disturbance in experimental forensic entomology: carcass biomass loss and temperature.

Often carrion decomposition studies are conducted using a single carcass or a few carcasses sampled repeatedly through time to reveal trends in succession community composition. Measurements of biomass and other abiotic parameters (e.g., temperature) are often collected on the same carcasses but are rarely a focal point of the studies. This study investigated the effects that repeated sampling during experiments have on the decomposition of carrion, measured as both gross biomass (carcass plus fauna) and net biomass (carcass only), on carcasses disturbed on every visit (with weighing only or also with the collection of fauna) and on carcasses disturbed only once. Each trial lasted at least 21 days, with samples taken in triplicate. Rat carcasses used in this study were placed in the field on the same day and either weighed on every visit or ignored until a given day. Internal and ambient air temperatures were recorded on each carcass at the time of sampling and on undisturbed carcasses using temperature loggers. The presence of succession fauna did not result in significant biomass loss on most days; however, there were individual days early in decomposition (days 3 through 6) when the succession fauna comprised a large portion of the gross biomass. With the exception of biomass loss by the emigration of maggots on days 4 and 5, neither repeated weighing of the carcasses nor repeated weighing and faunal sampling of the carcasses statistically affected the rate of biomass loss. Internal temperatures of carcasses sampled repeatedly were frequently 2-5°C lower than those that had not been disturbed, and ambient temperatures differed significantly depending on the location of measurement device. Results indicate that methods used historically for biomass loss determination in experimental forensic entomology studies are adequate, but further refinements to experimental methodology are desirable.