Abstract

When an organism dies, the process of decomposition begins and many insects are attracted to the decomposing remains, or carrion, as a prospective food source for themselves, or their offspring. Blow flies (Family: Calliphoridae), in particular, are one of the first insects to discover and colonize a dead body due to the ability to detect a decomposing resource from large distances. As a result, forensic entomologists take advantage of the behavior and developmental cycles of early colonizers to calculate the post-mortem interval (PMI) in order to determine the time since death. However, along with the insects that are attracted to the decomposing resource for food, other insect predators that prey upon these primary colonizers are also attracted. A common example of these predators includes the ubiquitous family of ants (Family: Formicidae, Order: Hymenoptera). Little is known regarding the impact that ant scavenging can have on the carrion insect community. To further understand the species interactions between blow flies and ants on carrion, two insect species were used: the green bottle fly, Lucilia sericata (Meigen), and the western harvester ant, Pogonomyrmex occidentalis (Cresson). Individual olfactory surveys were performed to determine if there was a preference to pork liver with L. sericata eggs. Results determined that there was a preference toward pork liver, regardless of the presence of L. sericata eggs (χ2 = 9.071, p=0.010722). Microcosm colony trials were also performed investigating the scavenging ability of ant colonies consisting of 30-40 workers. These results determined that P. occidentalis scavenging did not have a significant effect on pork liver (ANOVA p=0.078, Welch two-tailed p=0.078), but did have a significant effect on the removal of blow fly eggs (ANOVA: F 1,19 =6.359, p=0.021; Welch t-test: t 11.089 =-2.522, p=0.028). These results indicate that although P. occidentalis is attracted to fresh pork liver with or without the presence of L. sericata eggs, this species is more likely to prioritize blow fly eggs as a food source over fresh liver, exhibiting an average scavenging rate of 0.02149 grams of L. sericata eggs/ant/day. In forensic cases where ant populations are high in the vicinity of a corpse, ant scavenging on blow fly eggs could delay blow fly colonization. The results of this experiment help to further our knowledge regarding species’ interactions between ants and blow flies and how this interaction can ultimately effect PMI estimations.