Effect of body mass and clothing on carrion entomofauna

Abstract

Carcass mass largely affects pattern and rate of carrion decomposition. Supposedly, it is similarly important for carrion entomofauna; however, most of its likely effects have not been tested experimentally. Here, simultaneous effects of carcass mass and clothing are analyzed. A factorial block experiment with four levels of carcass mass (small carcasses 5-15 kg, medium carcasses 15.1-30 kg, medium/large carcasses 35-50 kg, large carcasses 55-70 kg) and two levels of carcass clothing (clothed and unclothed) was made in a grassland habitat of Western Poland. Pig carcasses (N = 24) were grouped into spring, early summer, and late summer blocks. Insects were sampled manually and with pitfall traps. Results demonstrate that insect assemblages are more complex, abundant, and long-lasting on larger carcasses, whereas clothing is of minor importance in this respect. Only large or medium/large carcasses were colonized by all guilds of carrion insects, while small or medium carcasses revealed high underrepresentation of late-colonizing insects (e.g., Cleridae or Nitidulidae). This finding indicates that carcasses weighing about 23 kg-a standard in forensic decomposition studies-give an incomplete picture of carrion entomofauna. Residencies of all forensically relevant insects were distinctly prolonged on larger carcasses, indicating that cadaver mass is a factor of great importance in this respect. The pre-appearance interval of most taxa was found to be unrelated to mass or clothing of a carcass. Moreover, current results suggest that rate of larval development is higher on smaller carcasses. In conclusion, this study demonstrates that carcass mass is a factor of crucial importance for carrion entomofauna, whereas the importance of clothing is small.

Keywords: Carrion insects; Coleoptera; Diptera; Forensic entomology; Forensic science; Postmortem interval.

Fig. 1

Effect of carcass mass and clothing on the number of taxa in adult or larval Diptera (a and b) or Coleoptera (c and d). Carcass mass: small 5–15 kg, medium 15.1–30 kg, medium/large: 35–50 kg, large: 55–70 kg. The line indicates the mean; the filled and empty circles indicate raw data

Fig. 2

Effect of carcass mass and clothing on the abundance of insects averaged across the most important taxa of adult or larval Diptera (a and b) or Coleoptera (c and d). Number of individuals from a given taxon collected on a given carcass was expressed as a portion of a total number of individuals from that taxon collected on all carcasses in a given block. Carcass mass: small 5–15 kg, medium 15.1–30 kg, medium/large 35–50 kg, large 55–70 kg. The line indicates the mean; the filled and empty circles indicate raw data

Fig. 3

Effect of carcass mass and clothing on the residency of insects averaged across the most important taxa of adult or larval Diptera (a and b) or Coleoptera (c and d). Residency was defined as a period of a taxon presence on a carcass. Carcass mass: small 5–15 kg, medium 15.1–30 kg, medium/large 35–50 kg, large 55–70 kg. The line indicates the mean; the filled and empty circles indicate raw data

Fig. 4

Effect of carcass mass and clothing on the interval between appearance of first and third instar larvae of Lucilia caesar (a) or Creophilus maxillosus (b). Carcass mass: small 5–15 kg, medium 15.1–30 kg, medium/large 35–50 kg, large 55–70 kg. The line indicates the mean; the filled and empty circles indicate raw data