Parasitoids and PMI

Necrophagous taxa can get attacked by a special guild of insects called parasitoids. According to Godfray (1994), a parasitoid larvae feed exclusively on other arthropods, mainly insects, resulting in the death of parasitoid's host. They represent an extremely diverse group, mainly Hymenoptera, and constituting about 8.5% of all described insects (LaSalle and Gauld 1991, Godfray 1994). Fabritius and Klunker (1991) listed for Europe 83 parasitoid species, which attack the larval and pupal stages of synanthropic Diptera. The life-cycles of the common parasitoid species are known (e. g. Geden 1997) and even if the adults have already emerged and left the host, the pupal exuviae of the parasitic wasps can be identified a long time afterwards (Geden et al. 1998, Carlson et al. 1999). Despite their great number and our growing knowledge about their biology there are just few reports on the use of parasitoids in forensic entomology (Smith 1986, Haskell et al. 1997, Amendt et al. 2000, Anderson and Cervenka 2002, Grassberger and Frank 2003b, Voss et al. 2009). Especially pupal parasitoids of Diptera could play an especially important role in the estimation of the postmortem period as they hit the host stages in a well defined window of time at the beginning of their development (Anderson and Cervenka 2002). This means that the calculated developmental time of the parasitoid just has to add to the time of development of the host (e. g. Grassberger and Frank 2003b), therefore providing an extended PMI timeframe in cases where traditional forensic indicators have completed their development. However, when thinking about the potential influence, especially of larval parasitoids, it is important to take into account that they also could create significant problems for forensic entomology: Holdaway and Evans (1930) described e. g. the change of developmental times for Lucilia sericata after the attack of its parasitoid Alysia manducator which resulted in a premature pupariation. This clearly illustrates the need for further research in this field.

0 0

Post a comment