Parasitic Insects, Mites and Ticks: Genera of Medical and Veterinary Importance/Houseflies and similar

House-flies, Stable-flies and similar flies (Diptera)
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Characters of a group of non-biting flies and biting flies (sub-order Brachycera)
These flies are all are brachycerans, with short antennae of a few dissimilar segments. The antennae consist of three short segments that lie in a groove in the head, and the large outermost segment has a distinct extension as an arista.

Most species in this group are free-living, but there are many ways some of them have adapted to parasitism. Adaptations of mouthparts of these flies often do not correspond with the taxonomic position of the fly. Mouthparts vary from surface sponging type (as with Musca) to a skin-piercing proboscis (as with Stomoxys).
 * Photograph shows a live Stable-fly, genus Stomoxys, with large eyes, characteristic antennae, one pair of powerful wings, and long piercing mouthparts protruding forward from head. (Photograph by Pavel Krok).

The life-cycle of most flies in this group is a simple complete metamorphosis, with eggs laid in the external habitat of the larvae such as organic waste, pupation in the same habitat, and adults parasitic on domestic animals. However, the Tsetse-flies are specialized for high survival of their larvae by rearing them one at a time.

House-flies and similar flies (Muscidae) are the familiar muscid flies common around human housing and livestock enclosures. The Eye-flies (Chloropidae) consist of several genera of small flies that cluster at the head and eyes of livestock animals, feeding on tears and mucous secretions; one example genus is described here. Stable-flies and Horn-flies (Muscidae) and Tsetse-flies (Glossinidae) are typical muscid flies in general structure and appearance, often superficially similar to Musca species. (Note that former genera Lyperosia and Haematobosca are now merged with Haematobia).

Mouthparts of Stable-flies, Horn-flies and Tsetse-flies are adapted for piercing the host's skin to feed on blood. These mouthparts are conspicuous as a stout proboscis that projects forwards; the labellum is not adapted as a sponging organ. These flies search for hosts during daytime; both females and males feed on blood.

The life-cycle of Stable-flies and Horn-flies is a normal complete metamorphosis type with free living larvae. The life-cycle of Tsetse-flies is highly adapted to blood-feeding parasitism. Both sexes feed exclusively on blood. A female takes repeated feeds to support development of one larva at one time within its oviduct. The mature larva is laid on sandy soil, where it rapidly burrows then pupates (see photograph under genus Glossina). The female repeats this larviparous method of reproduction to sustain the population.
 * Diagram of feeding at skin represents surface sponging by House-flies and others. There are no piercing elements in the mouthparts but some species have small rasping teeth within the sponge structure.


 * Diagram of feeding at skin represents the blood feeding by Stable-flies, Horn-flies or Tsetse-flies, by piercing into dermal capillaries with a stout proboscis type of mouthparts.

Glossary

 * Arista = A thin extension of the outermost segment of the antenna, it may have additional fine setae giving an appearance like a feather (7 on Musca).
 * Discal cell = An area of the wing defined by veins and forming a characteristic angular shape (6 on Glossina).
 * Empodium = A thin extension like a seta at the end of the feet, between the pulvilli (4 on Musca).
 * Hypopleuron = A specific area of the thorax of flies; in this group of flies it is without a row of setae, but with setae in Blow flies such as Calliphora.
 * Labellum = A paired organ (two labella lobes) at end of labium of the mouthparts of dipteran flies; well developed in muscid and tabanid flies where they are used like a sponge for feeding; or small and sharp as in Stomoxys where they are piercing organs (6 on Musca or 7 on Stomoxys).
 * Larvipary = Reproduction by giving birth to a mature larva which developed from an egg retained in the female's oviduct.
 * Prestomal teeth = small rasping teeth at the tip of a sponging labellum (8 on Musca).
 * Proboscis = General term for mouthparts of an insect that combine to form a stout piercing organ (9 on Haematobia).
 * Pulvillus = Pads on the ends of legs of insects and acarines, with adhesive properties (4 on Musca).
 * Tibia = Second to outermost segment on legs, may be equipped with a spur (5 on Hippelates).
 * Vein 4 = A wing vein that has a shape characteristic of genera of dipteran flies (5 on Musca).

Musca (Muscidae)
Characters: adult, lateral. 1- Eyes are large and dull red/brown. 2- Thorax does not have on its hypopleuron a row of stout setae (compare with Calliphora in  Blow flies ); thorax is dull black with four dorsal grey stripes. 3- Abdomen shows 4 visible segments (other segments are concealed at posterior); abdomen is dull mid brown. 4- Ends of the legs consist of a pair of claws, a pair of pulvilli, and a central empodium as a fine seta. 5- Wings have vein 4 curving sharply up towards the leading edge. 6- Mouthparts fold underneath the head when not in use. 7- Arista has setae on both sides. 8- Mouthparts extended for use reveal a labellum (sponging organ) and a pair of small palps. Also: arrow points to prestomal teeth between lobes of the labellum.

Hosts: Musca domestica (House-fly), M. autumnalis (Face-fly), M. sorbens (Bazaar-fly) and M. vetustissima (Bush-fly) are examples of the large number of species that feed on cattle, sheep and goats, pigs, horses, camels, humans and other mammals. Feeding is by sponging up wet secretions at the mouth, nostrils, eyes, teats, edge of wounds, and elsewhere. The ring of prestomal teeth at the end of the labellum may be used by some species to scrape at the skin surface to yield exuding liquid.

Disease: Nuisance through to severe irritation, leads to avoidance behavior. There is mechanical transmission of many types of microbial pathogens involved in mastitis. Moraxella bovis bacteria causing keratoconjunctivitis (Pink-eye) are transmitted to cattle by M. autumnalis which feed at the mouth and eyes. Musca species also transmit nematode worms: Habronema to horses, Thelazia to cattle and horses, and Parafilaria to cattle. Larvae of muscid flies typically inhabit dung piles and similar decomposing material, and the adult flies will feed on liquids there. Hence the very wide variety of potential pathogens associated with these flies.

Morellia (Muscidae)
Characters: adult, lateral. 1- Eyes are large and red/brown. 2- Thorax has its hypopleuron without a row of stout setae; thorax is black with dorsal grey stripes. 3- Abdomen shows four visible segments (other segments are concealed at posterior); dorsal abdomen is dull black, but white ventrally. 4- Wings have vein 4 curving evenly up towards outermost leading edge. 5- Ends of the legs consist of a pair of claws, a pair of pulvilli, and a central empodium as a fine seta. 6- Mouthparts when extended reveal the labellum (in form of a sponging organ) and a pair of small palps. Also: these flies are very similar to Musca but the body color and the shape of wing veins distinguish them.

Hosts: These Sweat-flies swarm around cattle and sheep seeking surface liquids to feed on.

Disease: Severe nuisance is caused.

Hydrotaea (Muscidae)
Characters: adult, lateral. 1- Eyes are large and red/brown. 2- Thorax has its hypopleuron without a row of stout setae. 3- Thorax and abdomen are dull black/green. 4- Fore-legs have a set of notches on their two largest segments. 5- Wings have vein 4 curving slightly towards outermost trailing edge. 6- Ends of the legs consist of a pair of claws, a pair of pulvilli, and a central empodium as a fine seta. 7- Mouthparts when extended for use reveal the labellum (in form of a sponging organ) and a pair of small palps.

Hosts: Hydrotaea irritans (Sheep head-fly) feeds on sheep and cattle at their mouth, nostrils, eyes and base of horns. This species has well developed prestomal teeth which they will use to scrape at the edge of skin wounds to release blood to feed on.

Disease: Irritation to severe biting-stress is caused by the feeding activity. Transmission of bacteria causing mastitis in cattle occurs.

Hippelates (Chloropidae)
Characters: adult, lateral. 1- Mouthparts are adapted for sponging. 2- Antenna has a spherical third segment which bears a prominent arista without setae. 3- Thorax and abdomen have only small setae, none of them resemble bristles; color is dull brown. 4- Vein 4 of wing goes directly to the outermost edge. 5- Tibiae of the hind legs have a prominent spur projecting backwards.

Hosts: Cattle, sheep and goats are troubled by these Eye-flies.

Signs and disease: Irritation is caused and there is potential for contaminative transmission of bacteria causing conjunctivitis.

Stomoxys (Muscidae )
Characters: adult, lateral. 1- Antenna has arista with short setae on the dorsal surface only. 2- Eyes are large and mid brown. 3- Thorax has a hypopleuron without a row of stout setae. 4- Thorax is colored black with prominent dorsal grey stripes; abdomen has a mottled pattern of grey and black dorsally, but is pale yellow ventrally. 5- Wing has vein 4 that curves evenly toward the lower outermost edge. 6- Wing has a discal cell of fairly symmetrical, trapezoid, shape. 7- Mouthparts project forward as a single proboscis when not in use; palps are much shorter than the proboscis.

Hosts: Stomoxys calcitrans (Stable-fly) and S. niger feed mainly on cattle and other bovids, preferring the legs and back. Stable-flies also feed on dogs, at their ears.

Signs and disease: Irritation leads to leg shaking and stamping. Biting-stress leads to substantial loss of production, particularly to dairy cattle when near the larval habitats.

Haematobia (Muscidae)
Characters: adult, lateral. 1- Similar to Stomoxys but approximately half that size. 2- Antenna has arista with short setae on the dorsal surface only. 3- Eyes are large and red/brown. 4- Thorax has a hypopleuron without a row of stout setae. 5- Thorax and abdomen are dull light brown. 6- Wing has vein 4 that curves evenly toward the lower outermost edge. 7- Wing has a discal cell of fairly symmetrical, trapezoid, shape; wings are held at an angle to the body when the flies are feeding forming a reflective angular shape. 8 and 9- Palps are as long as proboscis; mouthparts project forward as a single proboscis when not in use. Hosts: Haematobia irritans (Horn-fly) feeds mainly on cattle and buffalo, taking repeated small feeds during the day.

Signs and disease: These flies cause irritation, biting-stress, and avoidance behavior, leading substantial loss of production when these flies accumulate in massive numbers around cattle.

Glossina (Glossinidae)
Characters: adult, lateral. 1- Antennae have an arista with setae on the dorsal surface; these setae have additional extensions, making the arista look like a feather. 2- Eyes are dark brown. 3- Thorax has a hypopleuron without a row of stout setae. 4- Thorax and abdomen are dull light brown/grey in mottled patterns. 5- Wings have vein 4 curving in a wavy line toward the outer leading edge. 6- Discal cell of wings is distinctly asymmetric, shaped like an axe or hatchet. 7- When resting, wings are folded flat and overlapping. 8- Palps are as long as the piercing proboscis; the proboscis projects forwards when not in use.

Hosts: Cattle, a wide range of wild bovids, warthogs and other pigs sustain populations of these flies. Humans in endemic areas are readily bitten by these aggressive flies. (Tsetse-flies are commonly and correctly called simply Tsetse.)

Disease: Blood-feeding by these large flies is painful but loss of livestock productivity by biting-stress is poorly known. Tsetse-flies are notorious as the biological vectors of the Trypanosoma species of protozoa that cause nagana in cattle and sleeping-sickness in humans.

Distribution: Tsetse-flies are widely distributed in sub-Saharan Africa, but nowhere else. The species of importance to health, such as G. morsitans and G. pallidipes, mainly inhabit dry wooded savannah.
 * Photograph shows an adult female Tsetse-fly (Glossina) and a puparium that the fully mature pupa formed rapidly after being laid by a female.

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