Ephemeral and fluctuant, the fauna associated with a corpse provides a rich diversity of species. Several groups of arthropods are known to visit a carcass of a vertebrate at its various stages of decay; however, forensic investigations have so far been primarily limited to insects, focussing mainly on flies (Diptera) and beetles (Coleoptera) as often the largest and most persistent representatives. These insects might fly, walk or occasionally swim to reach the corpse and sooner or later abandon it in a similar way. Most will build transitional food webs that will lead to a faunal succession of species that will reflect the degree of decay under given environmental conditions.

From the very beginning, some insect and arthropod species will visit a dead body without laying eggs or showing signs of feeding that are destructive to the integrity of the body. These species might hold important information but do not leave behind any obvious marks of their former presence. Also species that will eventually colonise a body days or weeks later often visit the body early on. However, these insects don't come alone. Practically all of them will carry an extraordinary diversity of mites (Acari) with them, phoretic mites.

The Acari are a group of arthropods within the Subphylum Chelicerata or Cheliceriformes. Chelicerates differ conspicuously in their body plan in respect to the other arthropods. Their bodies are divided in two parts, the prosoma (front or anterior part) and the opistosoma (posterior part). Chelicerates do not have head, thorax and abdomen. The prosoma holds all the appendages; the chelicerae or mouthparts being the first pair, followed by the palps or pedipalps and four pairs of walking legs (in most adult forms).

University of Reading, School of Biological Sciences, UK H.R. Braig

Bangor University, School of Biological Sciences, UK M.L. Goff

Chaminade University, Forensic Sciences Program, Hawaii, USA

J. Amendt et al. (eds.), Current Concepts in Forensic Entomology, 69

DOI 10.1007/978-1-4020-9684-6_5, © Springer Science + Business Media B.V. 2010

According to their origin, the Acari are grouped into three major taxa. The Opilioacariformes is by far the smallest, accounting only for roughly 20 species placed in a single family of a single order, Opilioacarida (Walter and Proctor 1999). Opilioacariformes resemble small harvestmen (opilionids). The Parasitiformes includes ticks, which form the order Ixodida (also known as Metastigmata), and several species of mites parasitic on vertebrates in the orders Mesostigmata and Holothyrida. The Acariformes are all small mites encompassing three orders, the Sarcoptiformes, the Trombidiformes and the Endeostigmata. The Sarcoptiformes combine two well-known orders of an older but still widely used classification, the Astigmata and Cryptostigmata (or Oribatida), which assemble a huge diversity of soil species. The Trombidiformes (or part of the older order Prostigmata) combine many species of economic and medical importance.

Phoretic mites are not an occasional occurrence or an academic curiosity but an ecological consequence of the ephemeral and fluctuant nature of decomposition as a habitat. Regular changes in a habitat lead to an increased synchronisation of life history tactics of arthropods. Irregular, unpredictable disturbances lead to an increased representation of phoresy tactics (Athias-Binche 1994; Bajerlein and Bloszyk 2003; Binns 1982; Elzinga et al. 2006; Farish and Axtell 1971; Krantz and Whitaker 1988; Siepel 1995). In this chapter we would like to sketch some of the biological features of phoretic mites to outline the information these mites might provide for forensic investigations; information additional or complementary to entomological analyses.

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