Question

3. Ecological Categories Insect activity at a dead body can be divided into four major categories matching the ecological role they play. Some insects are attracted to a dead body and use the body as a source of food. Other insects are attracted to a dead body to feed on the first group, the insects that are using the body for food. "It's a bug-eat-bug-word, out there!" And some insects are attracted to a dead body to use as an extension of their habitat. Below are examples of each. (The links included direct you to optional BugGuide pages where you can read more about the insect groups.) 1. Necrophagous species: (the word necrophagous is from nekros, from the Greek meaning dead, and phagein, meaning to devour). Necrophagous insects feed on the body and are the most important species in establishing time of death because insects that find and use a dead body as a source of food arrive in a predictable sequence based on the state of decomposition of the body. These insects are referred to as indicator species. Examples: o Blow flies (Diptera: Calliphoridae) are metallic blue or green flies slightly larger than a house fly. They are also known as bottle flies. They are attracted to the odors of decay and may find a dead body within hours. The female fly deposits masses of eggs around body openings and the eggs hatch within 24 hours. The larvae feed on dead animal tissue though at times are found dung, and similar materials. When fully grown the larvae pupate on the body or in the soil under and around the body. Newly emerged adult flies will not return to the body to lay more eggs. o Flesh flies (Diptera: Sarcophagidae) are medium-sized and resemble the blow flies and house flies. Flesh flies are dull colored with black and gray stripes on the thorax and checkering on the abdomen. The flesh flies show up on a dead body slightly later than the blow flies. Flesh flies do not lay eggs. Instead the females deposit first instar larvae that were hatched internally, directly on the body. o House flies (Diptera: Muscidae) do not show up until the body is in advanced stages of decomposition. o Carrion or burying beetle (Coleoptera: Silphidae) adults may feed on decaying animal tissue, though their larvae feed on the fly maggots feeding on dead animals. They are therefore slight later to arrive on the scene than are the flies. o The larvae of carpet beetles and larder beetles (Coleoptera: Dermestidae) feed on dried organic material, including carrion. 2. Predators and parasites of the necrophagous species mentioned above are the second most important group in forensic entomology. These arrive after the first wave is wellestablished. Examples: o The larvae and adults of burying beetles (already mentioned) consume flesh, but also eat fly larvae found in the carcass. o Rove beetles (Coleoptera: Staphylinidae) prey on maggots that are feeding within carrion. 3. Omnivorous species: wasps, ants, and some beetles feed both on the corpse and its inhabitants 4. Adventive species: use the corpse as an extension of their environment, that is, primarily a place to hide. o Collembola- springtails o Spiders In some situations, based upon an understanding of the life cycle, habits and biology of these carrion-associated insects, the presence of particular species can provide not only clues to the time of death, but also to the general location of death (e.g. city vs. rural areas) and possibly whether the person died inside a building or outdoors. These clues are based upon the biological and ecological characteristics of a particular species; their life cycles, and seasonal and geographical occurrence.

The rate of development (that is, growth) of blow fly and flesh fly larvae is variable but predictable, which allows them to be used to estimate time since death. How are the age of maggots collected by a forensic entomologist at the scene, the surrounding environmental conditions, and the postmortem interval connected? This is supposed to be an easy question, even if awkwardly worded. Don't make it harder than it is. What external factor determines how quickly or slowly a maggot grows and therefore the age and the size of collected maggots?

Answer 1

Answer:- The age of maggot and postmortem interval are interlinked or we can call it connected with each other because when a person dies , as soon as person dies maggot finds it very soon by odour of the dead body and make it their food soruce and starts their developmental stage on the dead body itself. Hence forensic entomology use the method of determining the age of dead body by determining the age of maggots. Maggots age can be determined by observing their body colour and larval stage. As the fresh maggots which initially comes to dead body appear as metallic blue or green flies if the forensic entomologist find the dead body before hatchling of the eggs by maggot then they able to know that death of the person occurs is not more than 24 hours as female flies lay eggs in numerous numbers on the decaying body and hatching it within 24 hours and produce many first instar larval and the larva feeds on the decaying body and after fixed interval of time grown into second instar larva then into 3rd instar larva. The entomologist can easily determined in which larval stage maggot is reached by observing their number of spiracles present in the body . After 3rd instar they eat less and stop feeding on dead body and starts moving away from dead body and move to live in soil or clothes to pupate and then it encloses itself in she'll by loosening skill where it undergo metamorphosis to form adult fly and then the life cycle continues. When they developed into adult fly the left their shell in that place which indicates that they have completed metamorphosis. So the forensic entomologist have wide and clear knowledge about their developmental stage and time interval needed to complete each developmental stage and they determine it . And this developmental stage of maggot indicates the time period of death of person or how much time before the death occurs.

Environmental factors that affect on the development of maggot is temperature. Temperature enhance their metabolic rate and growth is speed up .