1. CARCASS BEETLES: (Trogidae)
Carcass beetles or hide beetles have distinctive warty or bumpy appearance.
They are called as hide beetles because they can hide themselves from predators
by covering their body with dirt and become motionless when they are disturbed.
They are found worldwide, family Trogidae includes 300 species with 4 genera.
They are 2.5-20 mm in length. Their shape is oblong to oval, with flat abdomen.
Their color ranges from brown to gray or black with dense setae.
They are found in dry environments instead of moist environments
They are scavengers and are among the last species to visit and feed on carrion.
They are most often found on the dry remains of dead animals.
Both adults and larvae feed on feathers, fur, and skin. Some species are found in
bird and mammal nests.
2. BODY CHARACTERISTICS
The head of these beetles is bent downwards and covered by the pronotum.
Their body shape is oblong to oval with a flat abdomen.
The antenna of hide beetles are usually short and clubbed.
The hardened elytra is covered with small knobs giving the beetle their rough
appearance. Elytra meet along the midline of body and cover the entire abdomen.
It bears well-developed wings. They also have heavy limbs and spurs.
Trogidae larvae are a creamy yellow/white in color, except at their caudal end
which darkens as it accumulates with feces.
Their heads are dark and heavily sclerotized.
The abdominal segments of hide beetles have at least one or more transverse rows
of setae.
4. LIFE CYCLE
After impregnation of the female by the male, the
female lay the eggs and the larvae hatches out.
Trogidae larvae have 3-5 instars.
During decomposition of a carcass, the beetle leave
its nest to feed on the carrion.
Both larva and adult can be found feeding on the dry
remains.
At the site of the carcass, an impregnated female will
dig small, vertical columns underneath the carcass to
lay her eggs allowing the larvae to locate food after
hatching.
5. FORENSIC IMPORTANCE
They can be the first in succession on burned and charred bodies.
After the burned skin is eaten away by the Trogids, the corpse allows
colonization by other forensically important insects that help determine
accurate Post mortem interval estimates.
Various species of Trogidae have been used by museums to clean up skeletons by
eating any remaining dried material left on the skeletons leaving them clean for
display. This method of bone-stripping has been used by some museums for
many years as it is the most effective method.
6. CARRION BEETLES: (Silphidae)
Silphid was described first in 1962 by Pearson.
They are commonly known as large carrion beetles, sexton beetles, carrion
beetles or burying beetles. About 200 species are found in the temperate regions
world.
The name carrion beetles shows their association with carrion, fungi,
decaying organic matter, and dung.
Families differ from each other on the basis of which family uses parental
care and which type of carcasses they prefer.
In forensic study they are used to help estimate a post-mortem interval (PMI).
They can feed carrion during all stages of decomposition (fresh, bloated, decay,
and dry).
Silphinae feed on maggots present on detritus until they are removed.
7. BODY CHARACTERISTICS
Silphid beetles are dark in color consisting of gold, black and brown.
The antenna is 11 segmented and is capitate (ending in a capped club). Subfamily
Silphinae show little to no care for their young and breed on large carrion.
Nicrophorinae breed on small animal carrion and will bury themselves and their
food to rear their offspring in a bi-parental manner.
Flight-capable species feed on vertebrate carcasses, whereas flightless species
will feed on soil invertebrates.
The larvae are black and appear armored.
Adults are 12-22 mm long. The pronotum is primarily a pale yellow with a black
spot in the center. Elytra are entirely black while in the northern portion they
have a yellow rear tip. The elytra are shorter than the body of beetle, leaving the
tail end slightly exposed.
8. LIFE CYCLE
The life cycle takes 26-58 days.
The larva undergoes 3 instars and develop in carrion within 10-30 days.
Larva venture away from the detritus to pupate in 3rd
instar.
Pupation takes 14-21 days. During this stage the wings become fully developed
and sexual maturity is reached.
Newly hatched adult is called as imago.
Oviposition is done near the carcass. It takes 12-48 hours for the eggs to hatch
into larvae.
At the height of breeding season pairs of beetles may compete for the carrion.
When there is large number of males are present in carrion, they try to boost up
their reproduction by emitting pheromones.
10. BEHAVIOUR
Mutualism: The beetle is known to engage in mutualistic phoresis with mites of
genus Poecilochirus. Upon arrival at a carcass, these mites drop from the beetle
and begin eating the eggs and larvae of the flies that preceded the beetles. They
eventually return to the adults and be transported to the next carcass.
Competition: Flies are major competitor of Silphiade for detritus. If a carcass is
infested with maggots, many of the Nicrophorinae abandon the carcass while
members of Silphinae feed on maggots. They are more active at night, nocturnal,
which help them to reduce competition with other organisms.
Parental care: The parental care exhibited by Nicrophorinae subfamily. Adult
regurgitate food into the mouths of the young larvae until they are mature. Adults
bury small animal carcasses and lay their eggs on it.
11. Defense: They have bright colors of their elytra, which serve as a warning to its
predators. They secrete a chemical from rectal glands which consists aliphatic
acids and terpene alcohols.
Locomotion and navigation: They are able to travel great distances to
find carcasses to breed and feed on. The hind wings are membranous and are
modified for flying or swimming. When an animal dies, hydrogen sulfide and
some cyclic compounds are released. Silphidae use their sense of smell to locate
carcasses from a long distance by chemoreceptors on their antennae, which are
adapted to detect these chemicals.
12. FORENSIC IMPORTANCE
They are very useful to determine post-mortem interval in medicocriminal
entomology. Time of death can be estimated on the basis of number of instars
present and stage of its life cycle.
When a pair of burying beetles comes across a carcass, they immediately work on
burying the body within few hours.
Members of family Silphidae are typically the first of the coleopterans to come in
contact with carrion.
Silphidae larvae are opportunistic predators that will feed on dipteran eggs,
larvae, and on the carcass itself. This presents a problem in the determination
of post-mortem interval (PMI) because Silphidae are known to eradicate other
species from carrion. By eliminating the first colonizing species Silphidae can
give an incorrect PMI.
13. ROVE BEETLES: Staphylinidae
Staphylinidae is the largest family of beetles, with over 54,000 species known
worldwide and probably over 75% of tropical species still undescribed.
Staphylinidae occupy almost all moist environments throughout the world.
They feed on decomposing fruits, decaying trees, drifted plant materials on banks
of rivers and lakes, and dung, carrion, and nests of vertebrate animals. larvae prey
upon mites, other insects, and small worms.
Many inhabit caves, underground burrows of vertebrate animals, and smaller soil
cavities, even of burrows that they (a few of them) excavate.
The larvae and adults have long, curved mandibles which are used for chewing.
They feed on carcasses (from the hours after death to the advanced stages
of decomposition), as well as on maggots that tend to be on dead animals.
14. BODY CHARACTERISTICS
The antennae are thick, beaded, and 11 segmented.
Larva is 20–25 millimetres long and are cylindrical and stout.
Most have short elytra, exposing several abdominal segments and cover the first
few abdominal segments. The adult is a shiny black color and 12–18 mm long.
They are slender with short elytra and powerful abdominal musculature that
renders them very flexible, thus able to enter narrow crevices.
The body appear longer when under moist conditions and alive, but shorter when
dried and dead.
They have needle-like jaws that close across in front of head and large, prominent
eyes.
Soil-inhabiting (Leptotyphlinae) and cave-inhabiting species are eyeless. Species
present in mountains, the soil, caves, and seashores are winglessness.
15. LIFE CYCLE
Eggs are white, spherical, spheroidal, or pyriform (pear-shaped). Female can lay
500-600 in total life span.The mated female deposits a cluster of eggs near a
source of food for her offspring.
Larvae are campodeiform/ staphyliniform. Rove beetle larvae typically inhabit
moist environments, such as in soil covered by decaying leaf litter.
Pupa is formed in moist leaf litter or in the soil.
Prepupae of Steninae, spin a silken cocoon. Pupae are obtect, pigmented, and
sclerotized in subfamily Staphylininae, but exarate, white, and unsclerotized in all
the other subfamilies. The immature stages develop rapidly, in a few days to a
few weeks, and the adults are long-lived.
When the adults emerge, they are very active, especially at night.
17. ECONOMOIC IMPORTANCE
Scydmaeninae and Oligota (Aleocharinae) as predators of
mites, Erichsonius (Staphylininae) as predators of soil-inhabiting
nematodes, Odontolinus and some Belonuchus,
Hesperus and Platydracus (Staphylininae) as predators on mosquito larvae and/or
pupae in water-filled flower bracts. Heliconia (Staphylininae) on adult dung-
inhabiting scarab beetles.
Rove beetle can infest in houses.
Some Belonuchus and Philothalpus (Staphylininae) occur in decaying fruits, and
eat fly larvae; adults of some Platydracus (Staphylininae) occur in carrion and eat
fly larvae and adults.
Biological control of fly larvae and other invertebrates have observed.
Staphylinids, including Tachyporus (Tachyporinae) as predators of cereal aphids,
and Aleochara as predators of root maggots (including augmentative use).
18. FORENSIC IMPORTANCE
Creophilus maxillosus can be used in investigative forensic entomology to
calculate the time of colonization or post mortem interval (PMI), both of which
usually prove helpful in general crime scene investigation.
Both larvae and adults of Creophilus maxillosus feed on the organic remains of
carrion as well as nutrient-packed diptera larvae.
They compete with maggots in carrion and their colonization continues
throughout the later stages of decomposition.
