True flies are insects of the order Diptera (from the Greek di = two, and ptera = wings). The most obvious distinction from other orders of insects is that a typical fly possesses a pair of flight wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax. (Some species of flies are exceptional in that they are secondarily flightless.) The only other order of insects bearing two true, functional wings plus any form of halteres are the Strepsiptera, and in contrast to the flies, the Strepsiptera bear their halteres on the mesothorax and their flight wings on the metathorax.
Reproduction and development
The genitalia of female flies are rotated to a varying degree from the position found in other insects. In some flies, this is a temporary rotation during mating, but in others, it is a permanent torsion of the organs that occurs during the pupal stage. This torsion may lead to the anus being below the genitals, or, in the case of 360° torsion, to the sperm duct being wrapped around the gut and the external organs being in their usual position. When flies mate, the male initially flies on top of the female, facing in the same direction, but then turns around to face in the opposite direction. This forces the male to lie on his back for his genitalia to remain engaged with those of the female, or the torsion of the male genitals allows the male to mate while remaining upright. This leads to flies having more reproduction abilities than most insects, and at a much quicker rate. Flies occur in great populations due to their ability to mate effectively and in a short period of time during the mating season.
The female lays her eggs as close to the food source as possible, and development is rapid, allowing the larvae to consume as much food as possible in a short period of time before transforming into adults. The eggs hatch immediately after being laid, or the flies are ovoviviparous, with the larvae hatching inside the mother.
Some species of flies act polygamously, meaning they mate with multiple partners. One such example of a fly that mates polygamously is the common fruit-fly, Drosophila melanogaster.
Larval flies have no true legs. Some dipteran larvae, such as species of Simuliidae, Tabanidae, and Vermileonidae, have prolegs adapted to such functions as holding onto a substrate in flowing water, holding onto host tissues, or holding prey. Roughly speaking, some anatomical distinction exists between the larvae of the Nematocera and the Brachycera (see Classification section, below); especially in the Brachycera, little demarcation is seen between the thorax and abdomen, though the demarcation may be very visible in many Nematocera, such as mosquitoes (see image, both here and in the mosquito article); in the Brachycera, the head of the larva is not clearly distinguishable from the rest of the body, and few, if any, sclerites occur. Informally, such brachyceran larvae are called maggots, but the term is not technical and often applied indifferently to fly larvae or insect larvae in general. The eyes and antennae of brachyceran larvae are reduced or absent, and the abdomen also lacks appendages such as cerci. This lack of features is an adaptation to food such as carrion, decaying detritus, or host tissues surrounding endoparasites.
Nematoceran larvae generally have visible eyes and antennae, though usually small and of limited function.
The pupae take various forms, and in some cases develop inside a silk cocoon. Despite the myth that flies only live a day (which may have either arisen from confusion with the mayfly or the fact that a fly inside a house may starve to death in a few days), most adult dipterans can live about one month.
Maggots
Maggots found on corpses are useful to forensic scientists, specifically forensic entomologists. Maggot species can be identified by various means such as their anatomy and by matching their DNA. Maggots of various species of flies visit corpses and carcases at fairly well-defined times after the death of the victim, and so do their predators, such as beetles in the family Histeridae. Thus, the presence or absence of particular species of fly maggots and other scavenger insects provide evidence as a basis for estimation of the time since death, and sometimes other details such as the place of death.
Some species of maggots are bred commercially; they are sold as bait in angling, and as food for carnivorous pets such as some fishes, reptiles, and birds.
In maggot therapy, larvae of certain flies in the family Calliphoridae are used to debride necrotic wounds.
In food production, certain cheese varieties, such as casu marzu, are exposed to flies known as cheese skippers, members of the family Piophilidae. The digestive activities of the fly larvae soften or liquefy the cheese and modify the aroma as part of the process of maturation.
0 komentar: