Worked examples of the necessary mathematics, including how to use excel to process data, coupled with lab protocols and self-assessment questions make the book an essential starting point in the subject. Assuming little prior knowledge of either biology or entomology the book provides information on identification, life cycles and ecology of insects presented in a forensic context.
Information is conveyed in an accessible style with practical tasks and suggestions for further reading included in each chapter. List of plates ix List of figures xiii List of tables xvii Preface xix Acknowledgements xxi 1 The scope of forensic entomology 1 2 Forensic entomology, DNA and entomotoxicology 12 3 Insects and decomposition 29 4 Identifying flies that are important in forensic entomology 42 5 Key for the identification of European and Mediterranean blowflies Diptera, Calliphoridae of medical and veterinary importance - adult flies 77 6 Identifying beetles that are important in forensic entomology 82 7 Sampling at the crime scene 8 Rearing insects and other laboratory investigations 9 Calculating the post mortem interval 10 Ecology of forensically important flies 11 The ecology of some forensically relevant beetles 12 Investigations in an aquatic environment 13 The forensic entomologist in court Appendices Glossary References Index Promote your book on NHBS.
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Butterflies Colouring Set 9. Flies are easily distinguished from other insects by having two fully developed, usually obvious, front wings, but with each of its two back wings modified into balancers, called halteres. These structures resemble tiny drumsticks. There has been a considerable change in fly taxonomy recently and the agreed groupings of flies arise from modern developments in taxonomy, including molecular studies.
In the older forensic text books, the taxonomy by Kloet and Hincks has been used. In this classification, the Diptera were divided into three suborders, with the third, the Cyclorrhapha, subdivided into the Aschiza, Schizophora-Acalyptratae and the Schizophora-Calyptratae. Lucilia sericata Figure 2. These insects have a long slender body, long antennae with more than six segments and a complex wing venation. The larvae of this suborder have a structurally distinct exserted head with horizontal biting mouthparts.
The pupa is not encased and so morphological structures such as wing buds are visible. The winter gnats Trichoceridae are an example of a nematoceran family which has members that are forensically relevant. They have been used to determine post mortem interval in the winter, when many other insects are no longer available. The second suborder is called the Brachycera, or short horns. They have shorter antennae than the Nematocera, with eight or fewer segments.
Their wing venation is less complex and their pupae grow inside a case which is the hardened remains of the last larval third instar coat. The male genitalia are separated into 2. The larvae have an elongated head which is combined within the first segment of the thorax prothorax. Their mandibles are divided. The Brachycera are split into groups infraorders , called the Tabanomorpha and Asilomorpha, which also made up the Brachycera under the old classification system. A third group infraorder , the Muscomorpha, is most important forensically. This group have antennae with a bristle and have three larval stages in which the morphological distinction into head and body of the larva is absent.
This group is subdivided into: In this division the depression and suture over the antenna is either absent or very indistinct. This is very long and closes, or almost closes, at a point at least more than half to two-thirds of the way to the edge of the wing. The Phoridae are of forensic note in this division. Usually, however, the anal wing cell in insects of forensic importance is short or even not there at all.
This is a feature of the Muscomorpha Schizophora, which includes the blowflies, cheese skippers and the fleshflies. This group is divided into two, depending upon whether or not there are flaps or calypters Figure 2. The Muscomorpha Schizophora Acalyptratae.
This deflates and draws back below the eyes and above the antennae. Its presence is indicated by a depression like a crease or furrow, just below the eyes, called a ptilinal suture Figure 2. Flies in this group do not have a thorax with sutures that completely divide the prothorax. The halteres are exposed and the antennae do not have a slit in segment three. Such flies are termed acalypterate. Of forensic note are the Piophilidae, Sphaeroceridae and Sepsidae. This calypter has a characteristic whitish coloured margin as in the Calliphoridae Figure 2.
The remains of the ptilinum is present as a ptilinal suture above the antennae 4. The Muscophora Schizophora Calyptratae. A division is made depending upon whether the halteres are exposed or covered. The opaque flaps concealing the halteres are termed the squamae or calypters; working from the body outwards, the proximal near flap is termed the lower thoracic squama and the distal far flap is called the upper thoracic squama.
Flies which have covered halteres also have a complete line, or suture, across the prothorax and prominent thoracic protrusions, called posterior callus, sticking out from the middle of the thorax. Such fly species may also have a slit or cleft in the second antennal segment working outwards from the head. According to Watson and Dallwitz , however, this is considered an unreliable feature for identification purposes. These flies also have a ptilinum. On the top or dorsal side of the antenna there is a feathery protuberance, called the arista, which stands out from the antennal segment.
Those flies with flaps covering the halteres and the features described above are termed calyptrate. Of particular forensic importance in this grouping are the families Calliphoridae, Sarcophagidae, Fannidae and Muscidae. Those of the female blowfly are more widely spaced than those of the male, as you look at them head-on from the front. Another important feature is occipital dilation of the eyes. To see if this feature is 2. It is possible to see if the eye is expanded. This occipital dilatation is used to distinguish some species Figure 2. The region below the eye, as you look at the fly face side-on lateral view , is called the jowl.
In Calliphora vicina, a species of forensic importance, this has a mass of golden coloured hairs on it. The families and the identification characteristics of some of the important species are described in the next section. However, to ensure that you have correctly identified a specimen, you should use keys, and have confirmed your identification using a collection of named species and the diagnostic and differential description in the handbook. Or you should ask a taxonomist to check your identification so that you are absolutely certain of the name of the species.
On this identification hangs the determination of the post mortem interval. For example, Schroeder et al. It is also recorded in the older literature as Calliphora erythrocephala Meigen. The front thoracic spiracle is orange in colour Smith, The head is black on top and the front half of the cheek bucca is reddish orange. The lower region of the face is black. There are black hairs on the jowls, irrespective of the jowl colour. The thorax is black and the top of the thorax the dorsum is covered with a dense greyish shine pubescence. There are a pair of strong bristles in a row in the centre of the thorax.
These are called the acrostichal bristles Figure 2. Like other blowfly species, this species also has a fan of bristles, the hypopleural bristles, on a plate above the coxa of each hind third leg, near the posterior spiracle. Look for this spiracle and you will spot them. The abdomen is blue with a silvery chequerboard effect tessellation Figure 2. The basicosta on the wing is yellowish in colour, although this can fade to a yellowish-brown colour. These are also large bluish-coloured blowflies. The species has a longer life cycle than the previous species and is more often found frequenting rural environments.
The hairs on the jowls and the colour of the basicosta help identify Calliphora vomitoria. The basicosta is black in colour Figure 2. The spiracle at the front anterior of the thorax is brownish in colour. Where both Calliphora vicina and Calliphora vomitoria are found together as third instar larvae, they can be separated, according to Smith , by the width of their posterior spiracles. He indicates that in Calliphora vicina the spiracles are 0. The spiracles in this species are smaller than in Calliphora vomitoria and are separated by the same, or a bigger, distance than the width of a single spiracle.
In Calliphora vomitoria the spiracles are larger, being in the region of 0. Its spiracles are separated by less than the diameter of an individual spiracle. Lucilia sericata Meigen This is commonly called a greenbottle because all the flies in this genus are a metallic green colour. In North America, Lucilia sericata is called Phaenicia sericata. Lucilia species are distinguished from other blowflies by having a ridge just above the squama, the rear wing flap hence the suprasquamal ridge , which has tufts of hair on it. Lucilia sericata has a yellow-coloured basicosta Figure 2.
One of the differences between the larvae of Calliphora and Lucilia sericata is that the oral sclerite in the head skeleton cephalopharyngeal skeleton is transparent and so seems to be absent in larvae of Lucilia sericata Figure 2. The identity of Lucilia sericata larvae can also be confirmed by looking at the Stem vein is bare in Lucilia species Figure 2. The protrusions found along the outer rim of the segment are called tubercles Figure 2.
They are named, from the top 12 noon position , the inner, median and outer lower tubercles. If the distance between the two inner tubercles is the same as the distance between the inner and the median tubercle, then this species can be identified as Lucilia sericata. This feature is characteristic of the third instar larvae. In Calliphora species these hairs would be visible under low power, being very well-developed in Calliphora vomitoria, but would not be visible under low power in Lucilia species.
Lucilia illustris Meigen The basicosta is blackish or brown in colour in this species and the arista on the antenna has up to 10 hairs on its underside. The males can be distinguished from Lucilia caesar Linnaeus males, by the presence of curved surstyli exterior structures of the genitalia Figure 2. This fly was found to be of value as a post mortem indicator in a murder in Washington State Lord et al. These flies are similar to Lucilia illustris in that they share a dark-coloured basicosta.
In males the sides of the second abdominal segment lacks bristles, when you look at the fly from the dorsal view i. They can also be a b Figure 2. In the Soham, Cambridgeshire, murder in , Lucilia caesar was found on the remains, although this was never used in court to identify the post mortem interval Hall, personal communication. Lucilia richardsi Collin In this fly the basicosta is white or yellowish, and the spacing of the eyes in the male assists in distinguishing this species from adult Lucilia sericata Figure 2. The abdominal sternites are hairy in both males and females Greenberg and Kunich, Smith indicates that the tibia of the middle leg has two anterior bristles, which also distinguish this species from Lucilia sericata, which has only one bristle the leg articulates in the posteroventral plane i.
Protophormia terraenovae Robineau-Desvoidy This species is 8—12 mm long. The fly has a greenish-blue abdomen, black-coloured legs and a dark calypter with hairs which are dark Figure 2. According to Figure 2. Phormia regina Meigen This is a smaller fly than those previously described and is a nearctic and palaearctic species. It is 7—9 mm long and has a green or greeny-olive coloured body.
Its head is large proportional to the body and is black in colour. A distinguishing feature in this species is the anterior spiracle on the thorax, which has obvious orange hair. In contrast to that in Protophormia terraenovae, the calypter is white, with white hairs. Phormia regina is commonly known as the black blowfly. Cynomya mortuorum Linnaeus This is a metallic blue-green blowfly which is about the same size as Calliphora species.
Its face and jowls are yellow to bright orange Figure 2. It is infrequently found in the south of England and MacLeod and Donnelly 2. The larvae of Cynomya mortuorum are associated with unburied corpses. Chrysomya species — Chrysomya rufifacies Macquart These are large blue or green flies. Chrysomya rufifacies is most commonly found in the orient, Australasia and the neotropics. It is metallic bluish or green in colour. The adults are 6—12 mm long, with at least the front part of the cheeks on the head being yellow or orange in colour Smith, Chrysomya rufifacies is one of the initial colonizers of corpses in Hawaii Goff, Its larvae have spines on the sides of their tubercles.
Chrysomya rufifacies is often accompanied by Chrysomya megacephala Fabricius , which is of a similar size. In contrast to Chrysomya rufifacies, the anterior spiracle of Chrysomya megacephala is orange to black-brown in colour, rather than being white to pale yellow. The front part of the cheeks bucca in this species is yellowish or orange. Chrysomya megacephala has also been identified from corpses along with Cochliomyia macellaria Weidemann , a native American species in Brazil Oliveira-Costa and de Mello-Patiu, Chrysomya albiceps Wiedemann is a third species which is found at crime scenes.
It has a yellowish or white thoracic spiracle, its abdomen has dark bands across it and its legs are dark. Larvae of Chrysomya rufifacies and Chrysomya albiceps are hard to distinguish visually. They are large and greyish in colour and have a chequerboard tessellated abdomen which is silvery grey and a thorax with three stripes down it Figure 2. Diptera, it is noted that there has been a division of the old genus Sarcophaga into a number of subgenera, resulting in a number of name changes from the early literature. It may be helpful to consider this in your reading of the earlier scientific papers].
Using the identity of the male, it is easier to confirm the identity of the female species. Help should be sought from taxonomists if these are the only family recovered from the body. The sarcophagid larvae are characterized by having a barrel-like shape with their posterior spiracles sunk into a hollow. The edge of the posterior segment has a large number of tubercles. This makes this family easy to distinguish as a larval stage. Some success has also been made in identification to species of larvae of the Sarcophagidae, using molecular methods Zehner et al. They have a head which looks spherical with bulging convex eyes and an abdominal constriction an apparent waist!
The legs of male sepsids have spines and are elongated, which makes the legs look deformed. The costa on the wing is unbroken. This family is characterized by its habit of wing-waving. There may be swarms of these flies at the crime scene, depending on its location.
Pont and Meier have revised the European Sepsidae and provide further details of their distribution as well as details of characteristics for identification. The costal vein of the wing appears broken at one point in this family. One of the most researched members of the Piophilidae is Piophila casei Linnaeus , which is a food pest on such products as cheese.
This fly is usually found on the corpse at the end of active decay and the start of the dry stages Byrd and Castner, It is a small black fly, 2. It has prominent cheeks which are more than half the eye height Figure 2. These flies have a yellow colour on their legs, antennae and on the jowls of their faces. Their ocellar bristles are found opposite the simple eye front ocellus , which are small and widely spaced. Piophilid larvae are similar to sepsid larvae, although the posterior larval region is narrower in the Piophilidae. The behaviour of Piophila casei larvae makes them easy to identify, as it is particularly characteristic.
If disturbed, the larvae bend round to grasp two small papillae on the posterior segment, using their mouth hooks. Other species of Piophilidae may also be present on corpses.
Therefore, do not make an assumption about the name of the species of piophilid which you have recovered from the body. They have a humped back and can be greyish-brown or bluish in colour. The forehead frons is usually wide, and has bristles which are very robust and upward curving. On the antenna the third 2. Phorid wings are characteristic; with veins 1—3 appearing very pronounced and crushed together.
The wing costa also has a spine at its proximal end, nearest the body of the fly. On a corpse, Phoridae can be identified by the fact that they are active flies, capable of running and jumping, and this gives them their common name of scuttle flies. Dewaele and LeClerq define their flight period as April to November. Wing veins 6 and 7 are short and do not move towards each other as they do in Fannia spp.
Their squamae are of roughly the same size, or the lower squamae may be bigger Unwin, As a rule of thumb, three DNA base pairs make a code for an amino acid. Mitochondria are the organelles in which ATP is predominantly manufactured. This allows compartmentalization of the mitochondrial biochemical processes.
The chemicals responsible for respiration electron transfer are bound to the inner membrane of the mitochondria. Knowledge of insect DNA is based on research on the fruit fly. The control region is also likely to be where the initiators for replication are located. Musca domestica is a greyish fly, about 6—7 mm in length.
It is characterized by four narrow black stripes along its thorax and a greyish or yellowish abdomen. A sharp-angled wing vein is found at vein 4 Smith, Musca autumnalis De Geer is also recorded visiting corpses Smith, According to Smith , female Musca autumnalis are very similar to female Musca domestica, but can be distinguished by a smaller frontal stripe.
In Musca autumnalis this stripe is less than twice the width of the eye, whilst in Musca domestica it is three to four times as wide. Musca autumnalis is rare in the north of England up to the borders of Scotland and is not found in Ireland. The larvae of the Muscidae are recognizable by the wiggly S-shaped slits on the posterior spiracles Figure 2. They are distinguished from the muscid flies by the much greater curve on the axillary vein vein 7; this is the vein which is nearest to the upper calypter and the species also lacks the sharp angle on vein 4, which reaches to the wing margin.
Fannia canicularis Linnaeus , the lesser house fly, is common in houses as it is attracted to light. Smith comments that this is the more common house fly until July. Benecke and Lessig recorded Fannia canicularis in a case of child neglect in central Germany. They are dull-coloured flies, 1. Their antennae are three-segmented with an arista. Vibrissae bristles are present on the sides of the mouth. The wing costa has two breaks and vein 6 is present, but does not extend to meet the wing margin.
Sphaeroceridae filter-feed on bacteria. Only a few species in this family are recorded from dead bodies. They have been noted from the fresh, bloat and advanced stages of decay the fifth wave of insects at 4—8 months after death. Grassberger and Frank recorded them on dressed pig corpses placed in an urban garden in Vienna between May and November Ammonia is an attractant for the dung-breeding flies.
Hence, voiding of urine early in decomposition can attract members of this family as much as ammonia release during later decomposition. Molecular biology has a role to play in providing an alternative means of insect identification using DNA. As in human somatic cells, insect cells contain genetic material in two places. It is also found in the cytoplasm as small circular structures in organelles called mitochondria. Both of these types of DNA are extracted in order to identify the life stages of insects, such as flies, collected from a body. Insect species identification using either mtDNA or nuclear DNA is based on the sequences of nucleotides on the chromosomes.
These sequences are called loci and are made up of an arrangement of sections of strings of base pairs of the nucleotides adenine, thymine, cytosine and guanine A, T, C and G which form the DNA molecule. The sections of base pairs which are used may be very short. To replicate the required regions of sample DNA, previously generated sections are joined to the sample DNA at known sites, to enable it to be copied.
These sections are called primers. Specific primers have been generated to identify calliphorid DNA Table 2. Some species identifications are based upon short sections loci on the DNA molecule, which can be fewer than significant base pairs. This means that, although the DNA chain degrades over time, insects which are stored, or which have dried out, can still be reliably identified using suitable primers. Both killing and preservation methods used at the crime scene, and subsequently, can influence the quality of the DNA which is recovered.
Using some preservatives can result in fragmentation of the DNA molecule. Any insect specimens chosen for DNA extraction should be taken from live cultures and killed by freezing. However, work by Lonsdale et al. Washing initially in bleach or acetone has been found to be satisfactory and does not affect the level of DNA preservation Fukatsu, ; Linville and Wells, Linville and Wells found that 2. A second precaution against contamination is to analyse the DNA from the head or thorax of the individual adult fly or the mid-section of a larva. This allows, as is necessary in all forensic work, the retention of voucher specimens in the form of the remaining body parts.
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Where possible in forensic work, the post-feeding stage should be used, or the larvae should be starved so that their gut is empty of food. This, too, prevents contamination by DNA, other than that of the particular individual species being investigated. The choice of extraction chemicals varies between laboratories. Once extracted, the fly DNA can be investigated further in one of three main ways: These will each be discussed under separate headings. If the numbers of strong peaks are few, Benecke suggested repeating the work using more primers. If the peak tops split, he suggested switching from the electrophoretic display Figure 2.
Benecke also pointed out that, to avoid getting false positives, samples from the same DNA source should never be loaded next to each other on the electrophoresis gel Figure 2. The advantages of using RAPD analysis are many. For example, because commercially generated primer beads are available, the process is quick; the room for experimental error and sample contamination during the analysis is reduced; the chemicals for RAPD analysis have a long shelf-life; and a large amount of information is recovered. Stevens and Wall used RAPD analysis to investigate variation between populations of Lucilia sericata from farms near Weybridge in Surrey and those from farms in the Bristol area.
As a control, they included specimens of Lucilia sericata from a laboratory culture at the University of Bristol. The results showed that closely related individuals of the species Lucilia sericata could be distinguished on the basis of their RAPD profiles. There are some disadvantages of using RAPD analysis of insect DNA, however, since the signatures gained for different species will not be standardized; no national or international databases exist from which to compare RAPD profiles of the insect species, and no statistical data are available in order to exclude chance when interpreting the results.
For these reasons, RAPD results are only 2. As a result, ATP is generated, using enzyme complexes called cytochromes, including cytochrome c oxidase, an enzyme complex made up of three subunits. This enzyme complex complex IV is found in the inner membrane of each mitochondrion and is the third and final enzyme for the electron transfer chain involved in mitochondrial oxidative phosphorylation. The insect mitochondrial DNA is a small circular genome containing around 16 base pairs of double-strand DNA, which comes predominantly from maternal sources Lessinger et al.
COI was originally chosen by molecular biologists to investigate genetic profiles, because it is the biggest of the three mitochondrially encoded cytochrome oxidase subunits and the protein sequence combines both variable and highly conserved regions Morlais and Severson, , quoting Clary and Wolstenholme, ; Beard et al.
Cytochrome oxidase is made up of: This is because it is rich in the nucleotides adenine and thymine and also controls replication of mitochondrial DNA and the transcription of RNA Avise et al. Mitochondrial DNA mtDNA is useful for insect species identification as it is, for the most part, resistant to degradation and its use can enable forensic scientists to provide identification of fly species within a day.
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For example, it was effectively used by Avise et al. Details of primer sequences, specifically relating to sequences of mtDNA in Calliphoridae, with the reference numbers L—7, can be accessed from GenBank Malgorn and Coquez, This information can then be used to request prepared primers from pharmaceutical companies. Ideally, primer enzymes that give a breadth of potential amplification should be used. Once extracted, the sequences of the protein-coding regions of the mtDNA, e. GenBank is a database of genetic profiles that are ratified and publicly available. Software such as Blast Search, which is accessed via the web www.
For example, Wells et al. A case study of the use of mtDNA analysis Wells et al. A live donor, who had had his liver removed for a transplant, was used in this research. A control was provided 2. DNA from both sources had the same characteristics Wells et al.
In a collection of maggots, subsequently identified as Chrysomya albiceps, was found on the floor of a farmhouse cellar in southern Italy. This was because in the interim the perpetrators had discovered that they had been betrayed and moved the corpse. Entomologically-aware police officers collected the maggots from the floor of the cellar to try to link this location with the earlier presence of the victim. The DNA content of the larval crops of the blowflies was analysed, together with material originating from the missing body.
The scientists confirmed that both samples of DNA were from the same sources. However, in this instance, restriction sites, which are fixed for a particular species, have to be determined before using the technique. This is a problem, since mutations can arise which affect the DNA signature and make its interpretation difficult. RFLP—PCR methods have been successfully used in forensic cases to assist in species identification, to allow post mortem interval determination. From these specific regions they clearly distinguished the species which are the three most common corpse-infesting flies in the Hamburg area.
DNA is not the only molecular means that has been used to characterize flies. Other chemicals, including allozymes, have been used for this purpose. These workers discriminated, on the basis of amount of hydrocarbons, between both the sexes and the three different geographic locations sampled. Differences in enzymes can be investigated by using electrophoretic techniques such as isoelectric focusing and isolating the proteins as bands on polyacrylamide gels.
Allozymes have been used in southern Australia to identify a range of blowflies commonly found associated with bodies Wallman and Adams, Four southern Australian species of fly were investigated. Using 42 allozymes, Wallman and Adams were able to show a clear distinction between the four species, both at third larval instar stage and as adults.
The main advantage of this method is its speed. Wallman and Adams were able to generate results in 3 hours, which is more rapid than is possible for DNA analysis. This method of analysis is also cost-effective and has a high level of reliability. They also point out that the method can be carried out in the field using equipment powered by portable battery packs. A disadvantage of the use of allozymes, which is often cited, is the production of weak banding patterns. Loxdale and Lushai suggest that this can be overcome by applying the sample accurately to the gel plate, investigating the buffers so that the most effective is used and keeping the reaction cool whilst electrophoresis is carried out.
Further studies need to be undertaken in order to develop this methodology, so that diagnostic markers for forensically important fly species can be reliably defined and the limits of variability can be confirmed, before this technique can have a natural place in the court room. Forensic genetic analysis of insect gut contents. American Journal of Forensic Medicine and Pathology 26 2: Molecular markers for the phylogenetics of mites and ticks. Systematic and Applied Acarology 7: Immature stages of British Calliphora and Cynomya, with re-evaluation of the taxonomic characters of larval Calliphoridae Diptera.
Journal of Natural History Eight squadrons for one target: Proceedings of the first European Forensic Entomology Seminar, 77 eafe. An alternative for the extraction and storage of DNA from insects in forensic entomology. Journal of Forensic Sciences 50 3: Mitochondrial DNA cytochrome oxidase I gene: Medical and Veterinary Entomology. Handbooks for the Identification of British Insects X 5c: Calliphoridae of Fennoscandia and Denmark. Fauna Entomologica Scandinavica Fine structure of eggs of blowflies Aldrichina grahami and Chrysomya pacifica Diptera: Identification of important fly eggs using potassium permanganate staining technique.
A Key to the Families of British Diptera. London [reprinted from Field Studies 5: A key to the adults of species of blowflies in southern Australia known or suspected to breed in carrion. Medical and Veterinary Entomology Useful websites on fly morphology and identification Look within the web page www. Other web addresses of interest include: Key to Fly Anatomy www. Beetles belong to the order Coleoptera and all share features in common. For example, they have biting mouthparts or mandibles, their antennae characteristically have 11 segments although in some species there may be fewer than this and the first section of the thorax the prothorax is usually distinctive in shape and size and can be used as an means of identifying the beetle.
The beetle exoskeleton is formed from hardened plates. The plates on the top surface are called tergites, the plates on the under-surface ventral are called sternites. The segment plates at the side lateral of the body are called pleurites the pleuron is the name for this region of the exoskeleton. Beetle adults are composed of a head, a thorax in three parts all fused together although the second and third parts are less visible dorsally and an abdomen. They have two pairs of wings; the two forewings are hardened and form a protective covering over the second, membranous pair of wings.
The prothorax is well developed and, together with the head, can be interpreted as a distinct anterior section of the body. The dorsal surface of the thorax is divided into the pro-, meso- and metanotum each plate, or tergite, is called a notum; plural nota.
The pronotum the surface of the first thoracic segment in front of the elytra is the biggest of the thoracic segments. It is made up of only one plate Figure 3. The ventral surface is correspondingly divided into three; the pro-, meso- and metasternum.
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The middle region of the thorax the mesothorax supports a pair of hardened wing cases which meet along the centre of the dorsal surface of the body. Part of the mesonotum is located between the base of the elytra, behind the pronotum; this small plate is called the scutellum. This pair of wings is folded under the elytra when the beetle is not in flight. They are generally designed for running or walking, but in some beetles, as in the Scarabaeidae, the front legs are also modified for digging Figures 3. The upper plates of the abdominal segments are sclerotized made of hardened cuticle due to the formation of a protein called sclerotin.
The lower abdominal plates the sterna are soft. A colour reproduction of this figure can be found in the colour section towards the centre of the book Beetle heads can be structured in one of several ways. They can project forwards horizontally a prognathous head , or orientate downwards a hypognathous head. Located on the head are the antennae, which carry tactile, heat-sensitive, olfactory and humidity receptors. The antennae of members of the Coleoptera vary in form. Some are thread-like filiform or plate-like lamellate , whilst others are elbowed geniculate or have club-like ends clavate.
Beetles exhibit complete metamorphosis during their life cycles and pass through an egg stage, larval stages and a pupal stage and emerge as an adult, or imago, each of which is morphologically different. Beetle eggs are frequently difficult to locate on or around the body, as unlike fly eggs they do not often appear in batches on a body. Beetle larvae have more distinctive morphological features than do the larvae of flies. For example, they have a sclerotized head capsule, and mouthparts which include mandibles are mandibulate. Larvae may or may not have legs on the thoracic region of their body.
Prolegs limbs on the abdominal region are rarely present in beetle larvae and this distinguishes them from the larvae of other orders. For example, ground beetle larvae carabids have an elongated flattened shape with well-defined legs that end in two claws. These are called campodeiform larvae. Scarab beetle larvae resemble a C—shape and these beetles tend to have a brown sclerotized head and a whitish body.
On the other hand, larvae of the dermestid family are particularly hairy on both the sides and the upper body surfaces and are recognized because of this coat of hairs. Examples of the shapes of forensically significant larvae are shown in Figure 3. Cuticle provides protection from physical damage and water loss and a rigid structure for muscle attachment, and limits growth to those times when the cuticle is newly developing.
The mechanical properties of cuticle depend on the quantity of protein present, the sequence of proteins and the degree of tanning sclerotization. Cuticle has three parts: The epidermis and cuticle together are called the insect integument. The epicuticle is the outermost layer. The outermost layer is a cement layer which prevents distortion of the next layer, a lipid—protein layer. Below this second layer is a glycoprotein superficial layer. The epicuticle does not contain chitin.
It is not capable of providing support or extending, but does provide waterproofing and protection against mechanical damage. Below this is the procuticle, which is 0. Procuticle is made up of a protein matrix in which layers of parallel microfibrils of chitin, an amino-sugar polysaccharide, are embedded to make a sheet. In the exocuticle the sheets of microfibrils are in the same plane, but each sheet may be orientated at a slight angle to the previous sheet. An alternate stacked or helicoid arrangement of microfibril sheets in the endocuticle results in it being a thicker layer than the exocuticle.
The darkening of the thinner exocuticle is due to tanning sclerotization. The basal layer beneath the cuticle is the epidermis. This single layer of cells is supported on a basement membrane which separates the exoskeleton from the main body cavity. Epidermal cells regenerate by cell duplication, or mitosis. This layer secretes the cuticle-forming chemical which is needed for moulting to take place. Types of cuticle There are two types of cuticle, soft and hard: Soft cuticle is flexible and the cuticle is thin and has little or no exocuticle.
Larvae predominantly have soft cuticle and a hydrostatic skeleton.
Soft cuticle is also important where movement is required and, for example, allows gravid females to extend their abdominal plates to lay eggs. Hard cuticle is hardened and armour-like because of the level of tanning, the positions of the microfibril sheets and hydrogen bonding between adjacent chitin molecular chains. Hardened chitin is found surrounding the spiracles of fly larvae and is present on the head and as the mandibles of beetle larvae.
It provides the strength and rigidity of the body and elytra in adult beetles. Reproduced from Munro with kind permission of Rentokil Initial plc Small, hardened structures projecting from the end of the larval abdomen are called urogomphi. They are recognizable, for example, in the larvae of Dermestidae, Nitidulidae and Histeridae.
The third stage of metamorphosis is called the pupal stage. The pupa has mouthparts which do not articulate i. This is not so in the staphylinids, where the pupa is covered by a hardened coat and the pupal appendages are held in place by secreted material an obtect pupa. In the third type of pupa c , the pupa is retained within the final larval coat; this coat is termed a puparium and the pupa is called a coarctate pupa. Reproduced from Munro with kind permission of Rentokil Initial plc Some pupae pupate in a chamber within the soil.
Others, like the scarabaeids, form a cocoon. In this instance the cocoon is made from material in the posterior section of the caecum Richards and Davies, The order Coleoptera is divided, on the basis of molecular studies, into what are treated as four suborders: Archostemata, Myxophaga, Adephaga and Polyphaga. The Archostemata is made up of three families which mostly inhabit decaying wood.
The Myxophaga are made up of four families which are aquatic or are found in wet habitats and are algal feeders. Although all insects may be of importance in forensic entomology, the remaining two suborders, Adephaga and Polyphaga, contain families of beetles which are most commonly found at crime scenes. The suborder Adephaga contains 10 families and comprises predatory beetles which inhabit terrestrial and aquatic habitats and includes the ground beetles, the Carabidae.
The Polyphaga contains families including the families Dermestidae, Scarabaeidae and Staphylinidae. The coxae of the third pair of legs the hind legs are fused to the metasternum. There are lines down the sides of the thorax called sutures the indents are positions where there is internal strengthening of the exoskeleton. An example of this is the suture between the notum and the sternum sutures are readily recognized a b Figure 3.
In the Adephaga the hind coxa is fixed immovably to the metasternum, i. It completely splits the first visible abdominal sternite. In contrast, in the Polyphaga the hind coxa is able to move, i. The majority of beetles in this suborder have thread-like filiform antennae. Larvae of insects in this suborder have legs with five segments which end in two claws only rarely is it one claw.
These larvae are mostly elongated and flattened Luff, ; in Cooter and Barclay, Most beetles in the Adephaga are predaceous; in consequence they may feed on the insects inhabiting a cadaver. The following features characterize this suborder. The hind coxa is rarely fused to the metasternum it moves, or articulates and so does not divide the first visible abdominal sternite. The thorax in this suborder does not have lines sutures across its dorsal surface.
The types of antennae in the suborder vary, so they cannot be used as an indicative feature. Polyphaga larvae are of many different shapes. They have legs with four segments which end in a claw. Some larvae in the suborder Polyphaga have legs which are reduced, others have vestigial legs, or the legs may even be absent altogether.
Polyphaga adults eat a variety of food. Some beetles are predaceous, but in the suborder as a whole many are phytophagous. Only beetles which are predators are of immediate importance to the forensic entomologist. A number of beetles visit a dead body, either because the body itself forms food and a habitat, e.
The families of insects from this suborder that are important in forensic entomology include the Silphidae, Staphylinidae, Histeridae, Trogidae, Dermestidae. The beetles of this family have antennae in which the sequence of antennal segments tends to thicken as the segments progress to the end, or the antennae are distinctly clubbed. The distance between the points of insertion of the antennae is wide. These are large, robust beetles and some, such as Nicrophorus vespilloides Herbst, have orange or red markings on their elytra. Others, such as Nicrophorus humator Gleditsch Figure 3.
If the beetle is turned over, six abdominal sternites are visible. They range in size from tiny to large. This family, however, are accomplished fliers and have strong membraneous wings packed away under their shortened elytra. This makes them look very aggressive and the action is reminiscent of a scorpion. If you see specimens reacting like this as you approach them, then you are most likely seeing a staphylinid beetle. Staphylinid beetles are predators and are attracted to the corpse to feed on the larvae of Diptera.
A number of species of rove beetles Staphylinidae have 3. Goff and Flynn recorded the presence of adult Philonthus longicornis Stephens from a 23 year-old Caucasian male in Hawaii; and Creophilus maxillosus Linnaeus , which Centeno et al. Their antennae are elbowed geniculate and the final segments of the antennae are formed into an obvious club.
Histerid legs have flat tibiae. The significant identification feature of this family, when looked at from above, is the square-cut to the ends of the elytra, which reveal the last two abdominal segments. Both larvae and adults are found on the corpse, as they feed on those insects attracted to decaying organic matter. The larvae also eat fly larvae and prey on other insects. The dorsal surface of the body appears roughened and the elytra can sometimes be hairy. The segments at the tip of the antennae are plate-like. The legs of trogid adults are not broad or modified for digging. Trogidae larvae characteristically have long, sharp claws.
Chinnery indicates that species of the genus Trox are not common in the UK. They are found at the dry stage on small carcasses and, in particular, feed on hide, fur, leather, feathers and dry matter. These beetles will also exhibit thanatosis if disturbed 3. Their antennae are made up of 5—11 segments, ending in a club made of two or three segments Peacock, Adult members of the genus Dermestes lack a simple eye an ocellus on the head. The coxa on the front leg is conical and sticks out prominently from the coxal cavity Figure 3.
The femur of the hind leg is covered by the hind coxa, which is flattened into a plate. These beetles have the capacity to pull all their appendages into the underside of their body so that nothing protrudes. Indeed, the larvae of Dermestes maculatus DeGeer Figure 3. They have one generation per year. Male Dermestes lardarius pass through four instars, whilst the female have five instars. The adults can be hairy. An example of a forensically significant member of the Cleridae is Necrobia rufipes DeGeer, the red-legged ham beetle, which can be found in association with bodies later in the decomposition sequence.
This species is a predator of fly larvae. The Nitidulidae have recently undergone taxonomic revision. The elytra are often truncated, but with rarely more than three abdominal segments visible dorsally. The fore- and mid-coxae are transversely orientated, whilst the hind-coxa is flattened. The tarsal formula for this family is most frequently 5—5—5 this means that the tarsus of each of the legs is made up of five tarsomeres. The first segment tarsomere of the tarsus is not shortened and all of the tarsal segments are more or less dilated. This family is a colonizer of corpses in the later stages of decomposition.
According to Cooter and Barclay , in the British Nitidulidae, the subfamily Nitidulinae includes two genera, Nitidula and Omosita, which are particularly associated with bones and dried carrion. All members of this family were recorded from the advanced stage of decay which occurred 13—51 days after the pig died. They can be found in a number of habitats, including grassland and forests. Carabids are members of the Adephaga because their first abdominal sternite segment is divided by the hind coxa. Their antennae are usually filiform, although some may be bead-like moniliform , and are located on the head, between the eyes and jaws.
The beetle head is prognathous. They are frequently fixed in position and, where this is the case, the beetle has only the vestiges of membranous wings. Carabid larvae are long or elongated in shape. The larva has a pair of sharp pincer-like mandibles and six simple eyes ocelli down each side of the head. The larval abdomen has 10 segments and on segment nine there is a pair of cerci. The larvae have legs which end in two claws.
Carabid larvae are very quick in their movements and tend to be nocturnal, so they may not be obvious members of the corpse assemblage. Indeed, these techniques are also used in phylogenetic investigations of beetle species, such as that undertaken to separate members of morphologically similar ground carabid beetles of the Nebria—Gregaria group, on Queen Charlotte Islands in British Columbia, Canada.
Reproduced with permission of Dr M. The families investigated included the carrion beetles Silphidae , e. Mitochondrial DNA has also been used to identify the larvae of beetle species present on a body and also for additional purposes, such as identification of the human host from the gut contents of the larvae upon whom it had been feeding. Di Zinno et al. With the longer lengths of mtDNA, they were able to obtain a greater resolution of the genetic make-up of the family, providing an increased identification profile for use by the forensic entomologist.
They showed that within the cytochrome oxidase I gene, in both Necrobia rufipes and Necrobia ruficollis Fabricius, there was a high degree of heteroplasmy which did not express itself as much in Necrobia violacea Linnaeus , another species of clerid. This variation has to be considered when interpreting a profile from a specimen from the crime scene. Less research has been undertaken on the molecular profiles of forensically important Coleoptera than for the Diptera. However, since the techniques are in place, further profiling of beetle species will expand this base as more crime scene investigations occur.
Coleoptera in criminal forensic studies: DNA techniques for forensic entomology. Boca Raton, FL; pp — The Biology of the Coleoptera.
Slough, UK; 74 pp. The Coleoptera of the British Isles 6 vols. Handbooks for the Identification of British Insects 4 Royal Entomological Society of London. An Introduction to Principles and Applications. Dung beetles and chafers Coleoptera: Scarabaeoidea , 2nd edn. Handbooks for the Identification of British Insects 5 A Practical Handbook of British Beetles. Ecology and behaviour of ground beetles Coleoptera: