**1. Introduction**

Forensic entomology is the subfield of forensic science that relies on insects and related arthropods for use in the judicial system. More specifically, the discipline uses information about terrestrial arthropods, namely insects (e.g., their occurrence, activity, seasonality), to draw conclusions about legal matters. Several species of insects are important physical evidence in issues relevant to civil, criminal, and administrative law [1]. By understanding the biology of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

necrophagous and synanthropic insects, predictions can be made as to why and when certain insects will become associated with human habitation, stored food, or colonizing a corpse. For example, several fly species are attracted to animal remains, including humans. Deciphering which species arrive in specific biogeographical and artificial (e.g., man-made) locations to a corpse, when during the decomposition process, and how long they take to complete develop‐ ment under varying environmental conditions, these insects become useful pieces of physical evidence in the investigations of homicides, suicides, and unexplained deaths [2]. The use of insect biology in this deductive manner is the basis for forensic entomology. However, forensic entomology is much broader than just death investigations. The legal issues addressed range from insects invading food and related stored products, to infestation of human habitation, to insect attraction to and use of animal remains. The latter also encompasses cases of neglect and abuse of humans and domesticated animals, as well as wildlife poaching. These exam‐ ples broadly define the three subdisciplines of forensic entomology: stored product entomolo‐ gy, urban entomology, and medicocriminal entomology [1]. Medicocriminal or medicolegal entomology has received a great deal of attention in the past three decades because of the direct impact on the human condition [3] and is the focus of this chapter.

What is the basis for insect usefulness in medicocriminal entomology? The keys are foraging behavior of necrophagous species and subsequent development of immatures on a corpse. Necrophagous insects recognize and are drawn to the odors emitted from the dead, especially from the remains of warm-blooded vertebrate animals [4]. No matter the size of carrion or location of a carcass (inside or outdoors), chemical signals associated with decomposition activate foraging in a wide range of saprophagous, predatory, and parasitic insects associated with carrion [5, 6]. This is particularly true of several families of flies. The linkage between animal death and necrophagous flies can be summed up with just one word: protein. For a female fly belonging to the families Calliphoridae and Sarcophagidae, animal tissues are rich sources of protein that are essential for producing or provisioning eggs [1]. Protein is so important to females that some males have evolved a keen chemical acuity to locate a freshly dead carcass with the goal of finding mates. The "need" for protein as well as other nutrients leads to intense competition for any type of animal remains. The fact that carrion is a finite source of nutrients, and that the occurrence (ephemeral) and location (patchy) of animal death are unpredictable, contributes to the frenzy in securing at least a portion of the nutrient prize [2]. So when a death event occurs in natural environments, many animals take notice and quickly mobilize for action. The same can be said for the occurrence of a corpse in a concealed location, with the realization that detection of emitted odors is slower and reaching a corpse is hindered by physical barriers such as seclusion in a dwelling, burial, or placement in an artificial container [1, 7]. Such barriers favor colonization by small-sized insects, but that is not necessarily what always occurs.

Competition for animal remains has shaped several aspects of the life history characteristics of insects that depend on the dead for survival. Nowhere is this more on display than with the reproductive strategies demonstrated by necrophagous flies. One group, the blow flies and bottle flies (Family Calliphoridae), is recognized as first responders to death [8]. In other words, many species are the earliest colonizers of carrion; often arriving within minutes of death or just after a corpse becomes detected. This generally means that adults are especially efficient at detecting and finding human or other animal remains [6]. Even in this shared pattern of early colonization by multiple species, there are several adaptations that permit various species to decrease competition with each other. For example, some blow fly species prefer large carcasses over smaller for oviposition; others demonstrate preferences for carrion placed in full sun, shade, or partial shade; and some are influenced by location on the body [7]. The latter is manifested in terms of depositing eggs in concealed locales such as natural body openings versus exposed on skin, hair, fur, or plumage. Many oviposit in exposed wounds, while others only deposit eggs on very moist surfaces such as in saturated soil or carpet under a body, or on clothing or hair/fur/plumage soaked in exuded body fluids. Even eggs and larvae are adapted for competition, as eggs hatch quickly so that neonates can begin a period of rapid and continuous feeding [9]. Larvae feed cooperatively in large aggregations (maggot masses) that maximize the rate at which larval development can proceed [10]. Maggot masses are unique microhabitats that permit larvae to thrive in carrion communities [1]. Importantly, the life history characteristics of these flies and the subtle nuisances that allow each to use a corpse differently, even if just slightly, contribute to resource partitioning. The latter is a necessity for necrophagous insects utilizing an ephemeral, patchy resource as a primary food source.

necrophagous and synanthropic insects, predictions can be made as to why and when certain insects will become associated with human habitation, stored food, or colonizing a corpse. For example, several fly species are attracted to animal remains, including humans. Deciphering which species arrive in specific biogeographical and artificial (e.g., man-made) locations to a corpse, when during the decomposition process, and how long they take to complete develop‐ ment under varying environmental conditions, these insects become useful pieces of physical evidence in the investigations of homicides, suicides, and unexplained deaths [2]. The use of insect biology in this deductive manner is the basis for forensic entomology. However, forensic entomology is much broader than just death investigations. The legal issues addressed range from insects invading food and related stored products, to infestation of human habitation, to insect attraction to and use of animal remains. The latter also encompasses cases of neglect and abuse of humans and domesticated animals, as well as wildlife poaching. These exam‐ ples broadly define the three subdisciplines of forensic entomology: stored product entomolo‐ gy, urban entomology, and medicocriminal entomology [1]. Medicocriminal or medicolegal entomology has received a great deal of attention in the past three decades because of the direct

What is the basis for insect usefulness in medicocriminal entomology? The keys are foraging behavior of necrophagous species and subsequent development of immatures on a corpse. Necrophagous insects recognize and are drawn to the odors emitted from the dead, especially from the remains of warm-blooded vertebrate animals [4]. No matter the size of carrion or location of a carcass (inside or outdoors), chemical signals associated with decomposition activate foraging in a wide range of saprophagous, predatory, and parasitic insects associated with carrion [5, 6]. This is particularly true of several families of flies. The linkage between animal death and necrophagous flies can be summed up with just one word: protein. For a female fly belonging to the families Calliphoridae and Sarcophagidae, animal tissues are rich sources of protein that are essential for producing or provisioning eggs [1]. Protein is so important to females that some males have evolved a keen chemical acuity to locate a freshly dead carcass with the goal of finding mates. The "need" for protein as well as other nutrients leads to intense competition for any type of animal remains. The fact that carrion is a finite source of nutrients, and that the occurrence (ephemeral) and location (patchy) of animal death are unpredictable, contributes to the frenzy in securing at least a portion of the nutrient prize [2]. So when a death event occurs in natural environments, many animals take notice and quickly mobilize for action. The same can be said for the occurrence of a corpse in a concealed location, with the realization that detection of emitted odors is slower and reaching a corpse is hindered by physical barriers such as seclusion in a dwelling, burial, or placement in an artificial container [1, 7]. Such barriers favor colonization by small-sized insects, but that is not

Competition for animal remains has shaped several aspects of the life history characteristics of insects that depend on the dead for survival. Nowhere is this more on display than with the reproductive strategies demonstrated by necrophagous flies. One group, the blow flies and bottle flies (Family Calliphoridae), is recognized as first responders to death [8]. In other words, many species are the earliest colonizers of carrion; often arriving within minutes of death or

impact on the human condition [3] and is the focus of this chapter.

necessarily what always occurs.

68 Forensic Analysis - From Death to Justice

Multiple groups of insects, not just calliphorids, utilize a decomposing body, arriving in waves to colonize a carcass when it is appropriate for progeny development and/or maximizes fitness of the mothers, or food/hosts is (are) abundant for predatory and parasitic species. For example, flesh flies (Sarcophagidae) can arrive in the first wave of colonizers or later during decompo‐ sition, and reduce the competition with blow flies by preferring small carrion instead of larger, depositing larvae (larviposition) instead of eggs, and the young of some species are predatory on other species [11]. Some fly species (families Phoridae and Piophilidae) do not lay eggs until the body is very dry, long after calliphorids and sarcophagids no longer have an interest in the body. Many species of beetles (Order Coleoptera) arrive early but generally after the initial wave of fly colonizers so that they can feed both on the corpse and fly eggs [12]. A few species of beetles (families Dermestidae and Cleridae) prefer dry remains, when the tissues are leathery in consistency and nearly devoid of moisture. Once the body has been reduced to bone, cartilage, and hair, insect interest wains but is not totally absent. A few moths (Lepi‐ doptera) will feed on hair and remnants of clothing, parasitic wasps (Hymenoptera) that specialize on wandering fly larvae or puparia scattered about the remains are present, and a small number of beetle species can be found searching for scraps on the bone [13]. By special‐ izing on different stages of decay, many organisms can successfully utilize the same resource, thereby forming thriving communities in a rapidly vanishing microhabitat.

Few of these "other" carrion inhabitants receive the attention of necrophagous flies. The net effect is that the potential of non-dipteran insects to serve as alternative forensic indicator species has not been examined in any detail. This chapter examines the parasitic Hymenoptera associated with carrion communities that offer potential utility to forensic investigations. The biology of the most common families of parasitic wasps is discussed in terms of how the life history characteristics relate to specific forensic applications.
