Sciency Thoughts: First evidence of Human consumption by Katydids and Woodlice.

Modern forensic science typically involves the detailed examination of corpses where foul play is suspected, with the aim of identifying any marks on the body, and relating them to the cause of, and circumstances surrounding, the death of the person in question. Numerous Arthropods are known to feed on vertebrate carrion, including Human remains, and marks left by feeding Arthropods have in the past been mistaken for burns, evidence of intravenous drug use, bite marks, defensive wounds and a variety of other forms of evidence. As such forensic scientists in a number of areas have begun to experiment with Human remains left to decompose in the environment, in order to better understand how Arthropod feeding traces and other forms of environmental destruction affect a body after death.

In a paper published in the Journal of Medical Entomology in January 2015, a team of scientists led by Jennifer Pechal of the Department of Biology at the University of Dayton and the Department of Entomology at Michigan State University, discuss the results of an experiment in which a body was left exposed at the Forensic Anthropology Center at Texas State University, and subsequently targeted by a variety of Arthropods not previously associated with the consumption of Human remains.

Firstly the cadaver was targeted by a gravid female Katydid, Pediodectes haldemani, which began feeding on the lower right arm of the body, approximately 32 hours after it was placed in the field. Katydids, Tettigoniidae, are Orthopteran Insects related to Grasshoppers and Crickets, but unlike these plant-eating groups they are generally omnivorous in their dietary preferences, and the species Pediodectes haldemani is known to be almost totally carnivorous. While Katydid have previously been recorded consuming vertebrate carrion, this is the first recorded instance of the consumption of Human remains by a Katydid, and Pechal et al. suggest that this might be slightly atypical behaviour, fuelled by a need for extra protein in the gravid female.

A gravid, female Pediodectes haldemani (Orthoptera: Tettigoniidae) feeding on the right forearm of a set of human remains (top), and the resulting physical artifact (indicated by the black arrow) on the remains by the feeding Pediodectes haldemani (bottom). Pechal et al. (2015).

Secondly the remains were visited by a Common Woodlouse, Armadillidium cf. vulgare, this time feeding on the lower left arm. Woodlice are terrestrial Isopod Crustaceans, with a typicalldetritivorous diet; they are most commonly associated with plant remains, but are known to eat carrion, though once again this is the first time that a Woodlouse has been recorded eating Human remains.

Armadillidium cf. vulgare (Isopoda: Armadilidiidae) feeding on the left forearm of a human set of remains (top), and the resulting artifact (indicated by theblack arrow) on the remains from the isopod activity (bottom). Pechal et al. (2015).

Finally the body was visited by a colony of Red Fire Ants, Solenopsis invicta, an imported species in the US, but which has become common in grasslands; Ants, including Red Fire Ants, are common visitors to carrion. On this occasion it is unclear whether the Ants actually fed on the remains, rather they entered the body via the hole left by the Katydid’s feeding and appeared to build a shelter there, using soil and small pieces of woody debris, a structure which would have been difficult to interpret had its construction not been observed.

A structure consisting of soil, small organic woody debris, and other organic material by red imported Fire Ants, Solenopsis invicta (Hymenoptera: Formicidae), in the artifact resulting from Pediodectes haldemani feeding activity on the leftforearm of the descendent. The structure was re-constructed each time the remains were disturbed for sampling purposes. The small dots surrounding the debris pile are fly artifacts or speck. Pechal et al. (2015).

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Monday, 2 February 2015

First evidence of Human consumption by Katydids and Woodlice.