Parasitic and predatory behavior of Alysia manducator (Hymenoptera: Braconidae) on blow fly larvae feeding on an adult pig carcass in the Western Cape Province of South Africa: preliminary observations and forensic implications.

Wasps are part of the entomofauna associated with vertebrate carrion. They are known to parasitize and prey on specific life stages of insect hosts such as eggs, larvae, pupae, and/or adults associated with vertebrate carrion. However, reports of parasitic behavior of wasps on carrion-associated insect life stages and their possible forensic implications are non-existent in the Western Cape Province of South Africa. This study is part of ongoing research investigating the entomofauna and their pattern of succession on an adult pig carcass in Cape Town, South Africa. During this study, the parasitic wasp Alysia manducator was noted parasitizing and preying on blow fly larvae associated with the decomposing carcass. The arrival of A. manducator coincides with the occurrence of blow fly eggs and/or larvae on the carcass. These wasps were seen in close association with the eggs and larvae of blow flies on various parts of the carcass and some wasps were seen dragging fly larvae attached to their ovipositors away from one part of the carcass to another. Some A. manducator were also observed walking over several larvae on the carcass while exhibiting a stabbing behavior presumably in search of a host for oviposition. We suggest that the observations recorded in this study are of considerable forensic importance as the dragging effect and predatory and stabbing behavior exhibited by A. manducator could potentially disrupt the feeding and development of the fly larvae on the carcass. This could subsequently alter the process of carcass decomposition and/or affect minimum post-mortem interval estimations.

Incidental observation of bone modification by Crematogaster cf. liengmei (Hymenoptera: Formicidae) in Cape Town, South Africa.

Different taxa of insects have been reported to modify the skeletal remains of vertebrates during feeding or the creation of their larval and pupal chambers. Anecdotal reports on the modification of skeletal remains by ants exist but are rare. In this paper, a case of modification of bone due to the feeding activity of the ant, Crematogaster cf. liengmei (Hymenoptera: Formicidae), is reported. In November 2022, a bone was encountered incidentally in the vicinity of the Table Mountain National Park. The bone had been colonized by several individuals of Crematogaster cf. liengmei. Several ants were observed feeding on and removing bone particles and soft tissue remnants. A closer observation revealed striae/furrows on the epiphyseal ends of the bone. A 60-kg pig cadaver used in a winter decomposition trial in the same area was similarly colonized by this ant species, resulting in soft-tissue modification. Due to the similarity in the striae/furrows observed on the bone and the bitemarks inflicted by the ants on the right ear of the pig cadaver in the vicinity, it was concluded that the striae/furrows seen on the bone were created by the ants. Our observations show that Crematogaster cf. liengmei is an important taphonomic bio-agent that can contribute to the modification of skeletal remains in terrestrial environments.

Caught in the act: impact of Crematogaster cf. liengmei (Hymenoptera: Formicidae) necrophagous behavior on neonate pigs (Sus scrofa domesticus L.) in the Western Cape Province of South Africa.

Ants have been documented as part of the entomo-sarcosaprophagous community. They have been known to alter the process of carcass decomposition due to their ability to feed on fly eggs/larvae and create post-mortem skin injuries. However, studies on the impact of ants on decomposing carcasses are scarce, especially within the Western Cape Province of South Africa. This study was part of a research project that utilized two (2) neonate pig carcasses in each month of the year to establish baseline data on the insect species associated with decomposing carcasses in the Western Cape Province of South Africa. In the early spring (September 2020), mid-autumn (May 2021), and mid-winter (July 2021) trials respectively, several individuals of Crematogaster cf. liengmei colonized the pig carcasses shortly after deployment. There, they fed on the flesh of the carcasses and further inflicted bite marks and conspicuous post-mortem skin lesions. Following the reduction in the presence of Crematogaster cf. liengmei specifically in the mid-winter trial, non-vital bleeding was observed as a consequence of the skin lesions. In the early spring, mid- and late autumn (May 2021), and early (June 2021) and mid-winter trials respectively, Crematogaster cf. liengmei prevented the formation of large maggot masses, principally through the predation of fly eggs, larvae, and adults. The observations recorded in this study are of considerable importance in forensic investigations as the effect of the necrophagous behavior of Crematogaster cf. liengmei on decomposing remains can be misinterpreted by inexperienced investigators during crime scene investigations and may alter post-mortem interval estimations.