**4. Future directions**

chewed in puparia reflect species preferences for emergence location and the size of the hole often typifies species [1]. Pupal exuvia also remain within the puparium, along with any unemerged larvae or pupae, providing clues regarding species identity and possibly devel‐ opmental duration, which are useful in establishing a PMI based on a particular wasp species and host. Such information has also proven useful to the specialized discipline of forensic archaeoentomology, in which parasitized puparia provided insight into the burial practices of

Molecular artifacts may also be associated with parasitic wasps, potentially revealing infor‐ mation regarding developmental conditions for the wasps and/or host species. The artifacts are in the form of heat shock proteins (hsps), produced in response to various stresses experienced during development, most frequently while progeny are feeding on fly hosts. For example, larvae of *N*. *vitripennis* demonstrate up-regulation of hsp 23, 60, and 70 when developing on hosts that have experienced overcrowded conditions in larval aggregations [52]. Hsp expression levels correspond with species and size of maggot masses experienced by the host. Similarly, fly hosts synthesize specific hsps in response to maggot mass dynamics, and the expression continues during pupal and early pharate adult development [62], a window of time in which pupal parasitoids oviposit on discovered flies. These observations suggest the possibility that molecular markers associated with hsp expression or associated with altered gene expression of other proteins may be useful in deciphering the developmental conditions experienced by parasitic wasps prior to discovery, and may also reveal limited but useful information concerning ambient temperatures realized by their fly hosts [52]. Much

Parasitic wasps do offer some advantages to forensic entomologists not yet exploited with necrophagous Diptera, namely in the form of chemical detection of decomposing bodies [43]. Under natural conditions, most species of parasitic wasps rely on chemical cues during foraging to locate potential hosts and their food resources [63]. At least with one species, *Microplitis croceipes* (Braconidae), a wasp that utilizes the larval stages of agricultural pests (Lepidoptera: Noctuidae) as hosts, can be trained through Pavlovian conditioning to associate a wide range of factitious chemicals with food [64, 65]. Odorants common to decomposition of animal tissues, that is, cadaverine and putrescine, have been used to successfully condition adult females, which, in turn, demonstrate foraging behavior in the presence of the odors [66]. Thus far the research is still in its infancy and has not yet been tested in a field setting to determine if *M*. *croceipes* can successfully locate a decomposing corpse emitting odors recog‐ nized by the wasps. For practical use, the parasitoids need to be tractable like has been done with honeybees, *Apis mellifera* (Hymenoptera: Apidae) equipped with GPS or radio signal detection when used as a sniffer system [67]. Other species have not been tested yet to determine how widespread is the ability of parasitic Hymenoptera to be used for the location of decomposing bodies. The technique would be especially valuable for finding concealed remains, such as buried, trapped in secluded locations, or those hidden in artificial containers.

more research is needed to determine if such possibilities are feasible.

pre-Columbian civilizations in Peru [42].

76 Forensic Analysis - From Death to Justice

*3.1.5. Biosensors*

Though parasitic wasps show tremendous potential to serve as alternative forensic indicator species, their full utility cannot be realized until key gaps in information are understood. Developmental thresholds and durations of development for most parasitoids are unknown. Any experiments performed to fill this void must take into account factors that influence the host-parasite relationship, as outlined earlier, and also consider optimal host-parasite ratios during parasitism [31]. The parasitoid fauna and seasonality based on biogeographical distribution are poorly understood throughout most regions of the world. What is known represents just a few parasitic wasps from a limited number of locations (Brazil, the United States, and parts of Australia and Europe), and even then, species from just a few locales within a region have been examined. This represents a considerable deficit in background information for application of parasitoid biology to medicocriminal entomology. Parasitoids are also known to alter the development of their fly hosts dependent on the parasitic strategy adopted yet few details are understood in terms of how this impacts the use of parasitic wasps in PMI estimations. For example, larval parasitoids such as *A*. *manducator* and *T*. *zealandicus* rely on a koinobiont strategy, whereby the host remains alive and in some cases, continues to feed following oviposition [26, 47]. Parasitism is not evident usually until pharate adult develop‐ ment of the fly host, which means that parasitized hosts may be used for estimations of the PMI. What is not known is whether the development of such hosts has been significantly altered by comparison to unparasitized flies. There is, thus, a need to examine the impact of koinobiont parasitoids on fly development and to uncover developmental markers relevant to staging both the flies and wasps. The latter is especially critical for species that utilize multiple stages of the same host, which likely are not equally suited for parasitoid develop‐ ment, and consequently would be expected to yield different developmental rates for a given parasitic wasp [26]. Host manipulation by idiobiont parasitoids is much different than occurs with a koinobiont strategy in that the fly typically does not continue to develop or only in a limited capacity following parasitism, and host death usually ensues quickly after oviposition [56]. That said the only detailed work with idiobiont parasitoids of carrion flies is with *N*. *vitripennis*, which is a pupal ectoparasitoid. Venom injected by females during oviposition alters several keys aspects of host physiology and development [68, 69]. In less desirable hosts for progeny development, such host alterations do not occur and larval development requires a significantly longer period of time to complete [70]. This again emphasizes the need for collecting data on developmental thresholds and durations of development for each host species of interest for each parasitoid encountered at a crime scene.
