Dipterans With Biting Mouthparts
As the name implies, these dipteran flies possess mouthparts adapted for puncturing the skin and obtaining blood meals. Feeding is achieved either through piercing-sucking mouthparts or by lacerating the skin and feeding from the resulting pool of blood. The mouthparts typically form a prominent proboscis equipped with sclerotized terminal structures used for skin penetration and withdrawal of the blood meal.
In some groups, such as black flies, sand flies, biting midges, mosquitoes, horse flies, and deer flies, only females take blood meals. In others, including stable flies, horn flies, buffalo flies, tsetse flies, sheep keds, and hippoboscid or louse flies, both males and females feed on vertebrate blood.
Dipterans With Nonbiting Mouthparts
As the name implies, some dipteran flies possess mouthparts adapted for sponging or lapping food from surfaces rather than piercing the skin. They feed on materials such as saliva, tears, mucus, wound exudates, and other liquid organic matter. Their mouthparts typically form a proboscis terminating in enlarged spongelike pads (labella) covered with fine hairs that facilitate fluid uptake from surfaces. Nonbiting dipterans include face flies, head flies, filth-breeding flies, and eye gnats.
Dipterans That Produce Myiasis
Larvae of certain dipteran flies can infect the skin, subcutaneous tissue, body cavities, or organs of living vertebrate animals, resulting in a condition known as myiasis. The two types of myiases are based on the extent of host dependence. In facultative myiasis, thefly larvae are usually free-living; however, in certain circumstances, these larvae can adapt themselves to a parasitic dependence on a host. In obligatory myiasis, the fly larvae are completely parasitic, ie, they depend on the host to complete the life cycle. Without the host, obligatory parasites will die.
The distinction between facultative and obligatory myiasis-causing flies is one of the most important concepts in veterinary entomology:
Obligatory myiasis-producing flies (eg, Chrysomya bezziana and Cochliomyia hominivorax) require living hosts for larval development. Their larvae feed on living tissue and cannot normally complete development in carrion or decaying organic matter.
In contrast, facultative myiasis-producing flies (eg, Lucilia sericata, Lucilia cuprina) can complete their life cycles without a living host. Their larvae commonly develop in carrion, decomposing organic matter, feces, or soiled wool. These flies only opportunistically invade wounds, fleece, dermatitis lesions, or necrotic tissue in animals.
This distinction has important implications for the management and prevention of myiasis. Because obligatory myiasis-producing flies (eg, Chrysomya bezziana and Cochliomyia hominivorax) depend on living hosts for larval development, they are responsive to area-wide control and eradication programs, including approaches using the sterile insect technique.
In contrast, populations of facultative myiasis-producing flies (eg, L sericata, L cuprina) persist in the environment on carrion and other decomposing organic substrates, even when access to susceptible animal hosts is decreased. Consequently, blowfly control in sheep focuses primarily on decreasing susceptibility to strike through measures such as crutching, breech management, prevention of fleece contamination, and prompt wound management, rather then attempting to eliminate fly populations from the environment.
In addition, accidental myiasis (referred to here as pseudomyiasis) occurs when fly larvae are inadvertently ingested or otherwise enter an animal without establishing a true parasitic infection and are subsequently recovered from the GI tract, feces, or other body openings.
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