For educational purposes:--
Information on the basics of Entomology
An Introduction To The Study of Entomology 1
Kingdom: Animalia, Phylum: Arthropoda
Subphylum: Hexapoda: Class: Insecta: Order: Diptera
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The Diptera -- <General Characteristics> <Juveniles> -- have only one pair of functional wings, hence their name meaning "Two-wing". The hind pair of wings is reduced in size to highly sensory stumps or halteres. The mouthparts are usually suctorial but sometimes piercing or biting, and elongated to form a proboscis. The prothorax and metathorax are small and fused with the large mesothorax. They have a complete metamorphosis. The larvae are often worm-like and always without legs. Their head is usually small and retracted. The pupa is either free or enclosed in a puparium that is made of the hardened last larval skin. [For terminology please refer to: Glossary]
This is a very large and specialized order of insects. The adults are mostly diurnal, feeding on the nectar of flowers, but a number are predaceous living on other insects (e.g. the robber-flies), while some, e.g. tachinids, are parasites. Several families have acquired blood-sucking habits, the representatives of which are of great importance because they harbor and transmit pathogenic organisms, causing such diseases as malaria, sleeping sickness, elephantiasis, yellow fever and some cattle fevers.
The food tube is formed mostly by the conjoined labrum-epipharynx and the hypopharynx, and at the lower end of the labrum where the latter structures do not reach the full distance. The overlapping sides of the labial groove form a food tube. In this way food collected at the median part of the pseudotracheal membrane to which the pseudotracheae converge is brought into contact with the food tube and so with the pharynx.
Calliphora feed largely on fluids, but in the presence of soluble solid food the groove solution is affected by regurgitating alimentary fluid onto it. In other cases the prestomal teeth can abrade temporarily dried surfaces and so bring the regurgitated fluids more effectively into contact with the food material. When the labellae are completely retracted food enters the wide-open food tube irrespective of the pseudotracheae and the passage is then large enough for semisolid food or even the eggs of helminths to enter (Borradaile & Potts, 1958).
It has been suggested that in the evolution of the Diptera there has been a trend towards surface fluid feeding involving the loss of piercing stylets. However, there are forms, closely related to the blowfly type in which mandibular and maxillary stylets are lacking, but which can pierce the skins of mammals, using the labium., e.g., the tsetse fly Glossina and the stable fly Stomoxys. In these cases the labium has become so rigid that it cannot be folded under the head. Therefore, with its contained labrum-epipharynx and hypopharynx, it extends stiffly forwards. The labellar apparatus is reduced and consists of three small, stout lobes that bear rasping teeth, some of which represent the prestomal teeth of Calliphora
Diptera larvae are among the most specialized of all insects. Legs have been entirely lost, and the head and spiracular system have undergone varying degrees of reduction. Thus the most generalized larvae are at the same time eucephalous, i.e. with a complete head capsule, and peripneustic, i.e. with the lateral spiracles on the abdomen, e.g. Bibio. In the most specialized forms, the acephalous larva's head capsule is absent, e.g. Musca. Such acephalous larvae may either be amphipneustic, with only prothoracic and posterior abdominal spiracles, or metapneustic, where only two spiracles exist at the posterior end of the body. The first instar larva of Musca is metapneustic, subsequent instars being amphipneustic.
The Suborder Orthorrhapha includes those flies which are liberated by means of a longitudinal split in the mid-dorsal line of the pupal case Such flies do not have a ptilinum. Many of these, the Nematocera, have slender antennae and usually pendulous maxillary palpi. Their larvae are eucephalous with transversely biting mandibles and their pupae are free. To this series belong the crane flies the larvae of which often damage cereal crops by devouring their roots. The Culicidae are the gnats and mosquitoes, the piercing proboscis of which has already been described. Their wings that are fringed with scales further distinguish them. Both larvae and pupae are aquatic, the former being metapneustic, the latter propneustic (with anterior spiracles only). With the blood-sucking habit of these flies has evolved an association with certain organisms that when, transmitted to humans, cause disease. Anopheles is concerned with the transmission of malaria. Stegomyia transmits the pathogen of yellow fever, while Culex fatigans, a widely distributed tropical form, is a carrier of the threadworm Wuchereria bancrofti, the cause of elephantiasis.
From this great assemblage of
flies the Tabanidae or gadflies, the mouthparts of which reference has
already been made, are of stout build and possess large eyes occupying a
great part of the head surface. Though a few transmit disease organisms (Chrysops
dimidiata, as the vector of the nematode worm Loa loa, is
responsible for calabar swelling in the natives of West Africa), the majority
are harmful chiefly through the annoyance that their bites cause. Tabanid
eggs are usually laid on the leaves of plants overhanging water and their
carnivorous larvae are either aquatic or ground-dwellers.
The robberflies (Asilidae) are large hairy flies with a proboscis that is pointed to the rear. They feed on all kinds of insects that they paralyze with their salivary fluid, and their legs, which are strong and equipped with powerful claws, are well adapted for grasping the prey. The Empidae, flies of more slender build, exhibit similar habits. Their larvae are terrestrial as are also those of the preceding tabanids.
The Suborder Cyclorrhapha are flies that emerge from a pupa which is enclosed in the last larval skin or puparium, and the commonly transverse or circular split in the latter, for release of the adult, gives the name to this suborder. Therefore, it is really a characteristic of the larvae that establishes the position of these flies in the classification.
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All species of Diptera have two wings, the hind ones being reduced as remnants to halteres, which vibrate in flight to act as a kind of gyroscope. This aids them in very rapid and agile flight. There are many aquatic larvae and their size ranges from minute to 16 centimeters long. The larvae are maggots with very few appendages. There is much mimicking of wasps and bees found in the order. The Diptera are important for their annoyance to or feeding on humans and animals, being disease carriers and some species are also injurious to plants.
The order is especially homogenous and is divided into to principal groups:
1. Nematocera have antennae with distinct segments varying from 5-30. Most larvae have a distinct head capsule, and the tentorium is developed so that the mandibles are opposable.
2. Brachycera have antennae with a reduced 3-4 segments. The head capsule is very much lost, and the larvae are worm-like maggots. The mouthparts are developed as hooks and function by moving up and down.
Mouthparts. -- There are three types found in adults: (1) nectar-feeding or sucking, (2) sucking-lapping or sponging and (3) true blood sucking that are rasping sucking. Simplified diagrams of these types are shown in the following:
Sucking (mosquito) Sponging (housefly Rasping-sponging (horsefly)
Larval Spiracular Arrangement. -- The spiracles of dipterous larvae may be arranged in either of four ways: (1) peripneustic,-- lateral spiracles on the abdomen. (2) amphipneustic-- only prothoracic and posterior abdominal spiracles present, (3) metapneustic-- only two spiracles are retained at the posterior end of the body. (4) propneustic -- lateral spiracles on the thorax.
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The following discussion includes only the most common or important families of Diptera. For greater detail please refer to Borror et al. (1989), and for an expanded treatment of Diptera taxonomy with 125 families noted please see < 207 Families>. Additional information on <Habits>, <Adults> and <Juveniles> is included when available.
Nematocera = "long antennae."
Culicidae. -- <Habits>; <Adults> & <Juveniles> -- The mosquitoes are identifiable by having scales present as patches on their wings. Only the female mosquito is capable of sucking blood. The eggs are laid in water and the pupae are capable of locomotion. There are two groups: The Anophelines and Culicines:
The wings are spotted with definite patches of scales. Their feeding position is at a 45-degree angle with the surface. The aquatic larvae feed horizontal with the water film due to short terminal spiracles. Members of the genus are the sole vectors of malaria. They have long palpi and the eggs are laid singly.
The wings are not spotted and mostly entirely clear. The feeding position angle is primarily horizontal with the surface. The aquatic larvae have developed an elongated siphon and feed hanging down from the water surface at an angle. Members of the genus include the common pest mosquitoes, which carry many viruses such as yellow fever, dengue, encephalomyelitis and the filarial worm. They have short palpi and the eggs are laid in masses.
Tipulidae. -- <Habits>; <Adults> & <Juveniles> -- The crane flies, which contain the largest number of species in the order, are recognized by their long, spindly legs. They have the appearance of giant mosquitoes, but there are no biting mouthparts in the adults.
There is a distinct V-shaped suture between the scutellum and scutum, and the adults lack ocelli.
Their habitat is primarily in damp areas with abundant vegetation, the larvae feeding in dead and decaying vegetation. The larvae of most species are aquatic or semi aquatic, and a few species feed on living plant tissue and thereby may cause damage to crops. There are even a few predatory species. Adults derive their nourishment from nectar.
Psychodidae. -- The moth flies and sand flies have abundant scales on their wings. They are small to very tiny insects with a large number of hairs on their bodies. When at rest adults may hold their wings roof like over the body.
The habitat is in moist shady areas but can also be found in drainages or sewers. Adults may occur in bathrooms that they enter via sink drains. Larvae inhabit decaying vegetable matter, moss, mud or water.
Chironomidae. -- <Habits>; <Adults> & <Juveniles> -- The midges also appear as very large mosquitoes, but they do not bite humans or animals. The male antennae are usually conspicuously plumose. They are one of the most abundant and important foods for fish in freshwater habitats worldwide. Most species are small and resemble mosquitoes but lack scales on their wings and are without a long proboscis.
The larvae of most members are aquatic, but several species also occur in decaying vegetable matter, under tree bark or in moist soil. Most are scavengers. Aquatic species usually form tubes or cases in which they are protected. Some species are red in color from the hemoglobin in their blood, hence their name, "bloodworms." The larvae may exist at varying depths in water, and they swim by whipping their bodies similar to that of mosquitoes.
Chironomids pose an annoyance because of the male's swarming habits. However, they are an important food source for freshwater fish and other aquatic inhabitants.
Simulidae. -- The black flies or buffalo gnats are biting flies that draw blood, especially around the head region of humans and animals. Their color is generally dark and they have short legs, broad clear wings with 4-5 veins. Their thorax is enlarged so that they appear hunch-backed. The females are bloodsuckers and can become vicious biters. Their bites may cause swelling or bleeding. In some parts of North America blackflies become so numerous that their attacks on livestock can cause death. Even humans have succumbed. Indeed, in areas of heavy infestation some communities hold "Blackfly Festivals" in late springtime to "celebrate" the end of the worst season of their occurrence.
They are associated with moving streams where the larvae develop underneath submerged stones to which they attach themselves with a disk like sucker at the rear end of their body.. The larvae possess gills, attachment hooks and characteristic respiratory horns.
Blackflies are vectors of animal diseases, especially of poultry, in some parts of the world. Diseases include onchocerciasis caused by a filarial worm, which may result in partial or complete blindness.
Ceratopogonidae (Heleidae). -- <Habits>; <Adults> & <Juveniles> -- The biting midges, punkies and no-see-ums are biting flies, with the Genera Culicoides and Leptoconops being especially problematic. Most species are very small and stout, with rather broad wings that they hold flat over their abdomen when resting. They are very pestiferous due to their habits of sucking blood from animals including other insects. The bites often result in painful swellings. Some species may be recognized by their spotted wings.
The primary habitat is along the seacoast and the shores of lakes and rivers. The larvae are aquatic or semiaquatic in the sand, decaying vegetation or mud and in tree holes containing water. Breeding along the seacoast is possible in the intertidal zone. Their habit of remaining close to the larval developmental sites allows one to simply move a short distance away to avoid being attacked.
One important species, the Hessian Fly, Mayetiola destructor (Say), attacks wheat stems in the larval stage. It was introduced into North America during the Revolutionary War with the Hessian insurgents. It is an important pest of wheat, barley, rye and some wild grasses. Injury is caused when the larvae burrow into stems, which results in stunted grain and sometimes in the death of the plant. The puparia overwinter in the grain. There are one or two generations per year. Control has involved planting wheat so that it germinates after danger of infestation is past, deep plowing grain stubble and reducing volunteer grain.
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Brachycera = "short antennae" includes larger flies with large eyes.
Tabanidae. -- <Habits>; <Adults> & <Juveniles> -- The horse flies and deer flies are vicious biters, and they inject toxic saliva into their hosts. The larvae are aquatic and predaceous. The adults may spread diseases such as tularemia and anthrax. Control measures involve draining swampland where the flies breed.
Bombyliidae. -- <Habits>; <Adults> & <Juveniles> -- The bee flies mimic bees in their appearance. Their bodies are fuzzy and they have fast flight habits. They are beneficial as their larvae are predaceous on many insect pests of economic importance.
Asilidae. -- <Habits>; <Adults> & <Juveniles> -- The robber flies are predators of other insects both as larvae and adults. They have what looks like a beard underneath their mouthparts. Adults can catch their prey on the wing.
Syrphidae. -- <Habits>; <Adults> & <Juveniles> -- The flower flies and syrphid flies adults are heavy bodied and have larvae that are predators of aphids especially. The larvae that frequent liquid animal dung are distinguished by having a rat-like tail. The wing has a spurious vein that is not a true vein, but is very useful in distinguishing species.
Adult syrphids are widespread in most habitats where they frequent flowers especially. Their habit of hovering around plants often gives them appearance of wasps or bees, especially those that are brightly colored.
The larvae have variable habits and appearances. Many species are predators of aphids while others occur in the nests of social insects such as termites, ants and bees. Other species inhabit decaying vegetation and rotting wood or polluted aquatic habitats. The maggots sometimes cause intestinal myiasis in humans.
Drosophilidae. -- <Habits>; <Adults> & <Juveniles> -- The pomace flies or small fruit flies have been used extensively in research on genetics. They have a very rapid life cycle, good taxonomic characters and giant chromosomes. They are especially attracted to fermenting plant juices. Their size is small, only 3-4 mm. in length and usually yellow in color.
Their primary habitat is around decaying fruits and vegetation, where they can cause some damage. The larvae live in decaying fruits and fungi where they feed primarily on yeasts that are present. Several species are parasites of Lepidoptera caterpillars and mealybugs.
Anthomyiidae. -- <Habits>; <Adults> & <Juveniles> -- The root maggots feed on roots up the crown of plants, which allows rots to enter the plants. The damage is especially severe in cold wet springs. Adults are attracted to decaying organic matter. The adults lay their eggs around the bases of plants and the larvae resemble housefly maggots. They overwinter in puparia.
Three very important species are the seed corn maggot, Hylemya (Delia) platura (Meigen), which is a pest on any vegetable seedling, the onion maggot, Hylemya antiqua (Meigen) that is a pest primarily on onion, and the cabbage maggot, Hylemya (Delia) radicum (Wiedemann) that primarily attacks cruciferous plants.
Control has involved the incorporation of insecticide into the soil, the chemical treatment of seed, the removal of culled vegetables from fields and the placement of cheesecloth over seedbeds.
Chloropidae. -- (Oscinidae) -- <Habits>; <Adults> & <Juveniles> -- The chloropids and eye gnats are small shiny black or yellow and black. They occur commonly in meadows and grassy places. They feed on grass stems and thus can be pestiferous on cereal crops. Some species are also scavengers and a few are predators or parasites.
The genus Hippelates has members that breed in decaying vegetation and animal dung and are strongly attracted to human and animal secretions. They have been noted to vector yaws and pinkeye diseases of humans. Considerable research has been done in California to combat this group of chloropids, either culturally, chemically or biologically (see ch-20.htm)
Tephritidae (Trypetidae). -- The fruit flies are a group that has many economically important species. The apple maggot and Mediterranean fruit fly are just two examples. The tephritids are fruit and vegetable feeders that may spread bacterial diseases to the fruit on which they feed. Their picturesque wings, which bear dark areas, identify the adults. Many species have been attacked with biological control because of the great difficulty in using other means of containment. (see bc-44.htm)
The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) has been imported repeatedly into North America and was twice eradicated in 1926 and 1956. It attacks citrus and other fruits in subtropical areas. Although California has experienced an incipient population through the 20th Century, there has never been damage to fruit reported there. Climatic limitations have been thought to be the reason for this. Nevertheless, there have been repeated eradication attempts with no data other than a reduction in bait trap collections following widespread insecticidal treatments.
The Oriental Fruit fly, Dacus dorsalis Hendel, invaded Hawaii during World War II. It caused widespread damage to fruits growing on the islands. Biological control projects have been launched to control this pest (see ch-82.htm)
The Walnut Husk Fly, Rhagoletis completa Cresson, invaded California from Texas causing widespread damage to the walnut industry. Parasites from the Davis Mountains area of West Texas have been imported for biological control (see efl231).
Muscidae. -- The house flies, face flies, horn flies, stable flies, tsetse flies and little house flies are all serious pests of humans and animals. The family may be identified by fleshy lobes, called squamae, located underneath the halteres on the sides of the thorax. Many species are also identified by chaetotaxy (arrangement of hairs on the body)
The importance of this family as serious pests and vectors of diseases has led to several biological control projects to contain them (see bc-37.htm).
The housefly, Musca domestica L. lays its eggs in decaying vegetable matter or animal excrement. . The legless larvae are maggots with mouth hooks, caudal and thoracic spiracles. Their filthy habits of regurgitating saliva and food cause them to be vectors of typhoid, cholera, and dysentery. etc. Either feces or regurgitations cause the flyspecks often found on surfaces. Houseflies have been the target of biological control in California and elsewhere (see ch-50.htm)
Tsetse flies, Glossina spp., are confined to the African Continent where they are vectors of trypanosomes that cause sleeping sickness and related diseases of humans and animals. These large, noisy flies may cause severe bites on humans with resultant swellings. In East Africa they are especially prevalent around streams.
Little house flies, Fannia spp., breed in large numbers in animal dung, and are especially numerous around poultry farms where they breed in such high numbers as to invade surrounding areas causing annoyance to residents. They appear as small houseflies hovering in huge masses. They have been the target of biological control in California and elsewhere (see ch-50.htm)
Calliphoridae. -- <Habits>; <Adults> & <Juveniles> -- The blowflies, bluebottle flies and screwworm flies are flesh feeders. They lay masses of eggs in dead animal carcasses. The presence of these flies is indicative of a dead animal.
Screwworm flies are attracted to wounds and some species are parasitic and able to penetrate living flesh. They are especially prevalent in southeastern North America. Females lay their eggs in wounds and the larvae invade surrounding tissue. They are especially serious pests of sheep.
Screwworms were periodically effectively reduced in number by the liberation of males that have been sterilized with radioactive cobalt. The females, which copulate just once, cannot produce progeny if their mate is a sterilized male. The flies were even completely eradicated from one island by the deployment of this technique.
Medication of wounds on animals is effective in control, but it is necessary to be on continuous alert for new wounds.
Wool maggots are attracted to soggy and wet wool, especially around the rump area. Precautionary control measures involve clipping the wool.
The maggots of some screwworm species are able to clean-up dead flesh from wounds and thereby cause rapid healing, especially for very deep wounds.
Sarcophagidae. -- <Habits>; <Adults> & <Juveniles> -- The flesh flies are similar to Calliphoridae, but they are usually black or gray with stripes on their thorax. Adults feed on sweet foods such as flower nectar, fruit juice and honeydew.
Their larvae show diverse habits, but most feed on animal material, with many being scavengers. Some species are scavengers, some are parasites of other insects and a few are parasites of vertebrates that develop in skin wounds.
Tachinidae. -- <Habits>; <Adults> & <Juveniles> -- The tachinid flies are a large family with representatives widespread in almost every habitat. They are valuable in natural control because their larvae are parasitic on other insects.
Tachinids tend to lay their eggs on the body of their host. The larvae then burrow into the host to feed internally. They leave the host to pupate. Some species that lay their eggs on plant foliage give rise to flattened larvae that are known as planidia. These remain on foliage until they are able to attach themselves to a host when it comes near. In other species the eggs must be ingested by a host caterpillar before hatching. These larvae then feed on the internal organs.
Oestridae (Gastrophilidae). -- The warble flies and botflies lay their eggs on the hair of the rear legs of animals. The larvae burrow into the shanks, pass into the intestines, burrow through the intestinal wall and eventually come to lie in the back of the animal just under the skin. This results in the hide being reduced in value because of ensuing fly exit holes in the back. Pupation occurs in the ground. Systemic insecticides have been used for control.
Several serious botflies, Gasterophilus spp., are discussed as follows:
Horse Botflies., -- These flies produce eggs that are swallowed by horses, after which the hatched spiny larvae attach themselves to the wall of the horse's intestines. Horses lose energy and weight following infection. The flies overwinter in their alimentary canal and the larvae mature in late winter or spring. The maggots attach themselves to the stomach lining. They detach in late spring and burrow into the soil to pupate. Adults emerge in early summer but do not bite.
Common Botflies. -- Female flies can lay over 800 eggs on hairs in the upper portion of the front legs of animals. The animal licks the area and the eggs hatch. The larvae live a short while in the animal's mouth and then are swallowed.
Throat Botflies. -- Eggs are laid on the throat, but stimulation by licking is not required here. The larvae hatch out and crawl into the animal's mouth where they feed along the gum line. Later the larvae enter the stomach where feeding continues.
Nose Botflies. -- This is the most serious of all the botflies, although it is less common. Eggs are laid on the upper lip of the animal. Moisture there induces hatching. The larvae then tunnel through the lips and into the mouth, causing severe soreness. They are then swallowed and enter the digestive tract. Control has involved keeping animals stabled during daytime, using repellent materials, sponging off areas with warm water and phenol, and providing internal dosages of carbon disulfide.
Cattle Grubs and Ox Warbles (Hypoderma spp.). -- Included are the Heel Fly and Bomb Fly. They are primarily pests of cattle, often infesting over 75 percent of a herd. The animals will lose weight, the hides are ruined and milk production falls.
During their life history in winter the larvae exist as cysts in the backs of animals under their hide. They feed on secretions from the irritations they cause. A breathing hole is cut through the hide. Maturity is in late winter. In springtime the larvae wiggle through the breathing hole and drop to the soil where they pupate. Adult flies are found in pastures through the summer and into autumn.
Adult flies lay eggs on the belly or legs of the animals, which become very annoyed by their buzzing. Bomb flies prefer to lay the eggs in sunshine on the belly and legs, while heel flies lay eggs in the shade on the heels. Ensuing larvae of bomb flies go directly to the back of animals, while larvae of heel flies migrate to the gullet area to feed, after which they move up to the back.
Sheep Nose or Bot Flies, e.g., Oestrus ovis L.) -- These attack sheep, goats, deer and rarely humans. They are responsible for nasal infections, insanity, blindness and even death. The larvae are deposited in the nostrils of animals after which they migrate to the brain area through the sinuses. They remain several months in the area underneath the horns. They then wiggle out through the nostrils and pupate in the ground. Containment involves painting the animal's nostrils with a repellant, such as pine tar, and to run sheep into dark sheds in daytime at the worst time of the year.
Hippobosidae. -- The louse flies and sheep ked eggs and larvae develop within the mother fly and are nourished from glands. The "nits" pupate immediately upon being released. The adults are either winged or wingless. The winged species are dark brown and about the size of small houseflies and are common on birds. The sheep ked, Melophagus ovinus (L.) is wingless and parasitic on sheep.
Control of these flies is relatively simple. Subjecting animals to various sprays, dips and dusts in autumn is usually adequate. Also by removing sheep from old pens and spraying the pen area with insecticides eliminates the flies.
Diptera --Biological Control Projects (11.2% of total projects)
Apple Maggot, Rhagoletis pomonella (Walsh) <ch-5.htm>
Aquatic Diptera <ch-118.htm>
Aquatic Midges <aqamidge.htm>
Bush Fly, Musca sorbens Wiedemann <ch-119.htm>
Chironomid Midges, Chironomus spp. <ch-19.htm>
Chloropid Gnats (Hippelates, Leptoconops, etc.) <ch-20.htm>
Flies in Accumulated Wastes, Musca domestica L., Stomoxys spp., etc <ch-50.htm>
Flies in Field Dung, Musca autumnalis, Musca vetustissima, Haematobia spp. <ch-51.htm>
Fruit Flies, Ceratitis, Dacus, Rhagoletis, etc. <fruit.htm>
Melon Fly, Dacus cucurbitae Coquillett <ch-73.htm>
Mosquitoes, Culex, Aedes, Anopheles, etc. <ch-74.htm>
Oriental Fruit Fly, Dacus dorsalis Hendel <ch-82.htm>
Examples of beneficial species occur in almost every insect order, and considerable information on morphology and habits has been assembled. Therefore, the principal groups of insect parasitoids and predators provide details that refer to the entire class Insecta. These details are available at <taxnames.htm>.