Biology

There is little information on the specific life cycle of Ceratopogonidae, especially in the Palaearctic region and their larval ecology is still unstudied (biting midges cannot be maintained in laboratory conditions).

The females lay their eggs on moist substrate or water. Breeding and larval habitats are not well known. The eggs are often joined to each other in a chain

Figure 1.8 Female Culicoides sonorensis blood feeding (Photo courtesy of P. Kirk Visscher).

of 60 to 250 eggs laid on mud, leaf litter, humus or plants near water, depending on the species.28 Incubation lasts two to 15 days according to temperature and species, but certain species hibernate (diapause) at egg stage. Larvae are important detritivores or predators in semi-aquatic and aquatic habitats of all sizes, with either freshwater, brackish water or even seawater (e.g. estuaries, mangrove or coastal ponds). The larvae are often localised in muddy habitats, in wet sites rich with organic matter of plant origin (e.g. tree holes, crab holes, trunks of banana trees, cacao, mushrooms, etc.). Some species develop well in sandy areas near the sea, which constitutes a nuisance on the beach. The larval development takes two to three weeks (in tropical regions), but can reach seven months (in temperate regions). The larvae feed on plants in decomposition. Pupae are generally sluggish and this stage lasts from two to ten days, then the adult hatches. The adults feed on flower and plant nectar; only the females are hematophagous, taking their blood meal from hot or cold blooded vertebrates. Certain species feed on hemolymph of other insects (e.g. Culicoides anophelis bites Anopheles mosquitoes in the Southeast Asia). Biting activity is variable according to species, but it is generally done during crepuscular or twilight, though some night biting also occurs. Biting behavior is usually exophagic. Swarms of biting midges will come to people for biting the head or any other exposed areas, their small oral parts do not allow them to bite into blood vessels such as mosquitoes, but they can dilacerate skin to suck the blood (pool feeding). This method of blood feeding allows the transmission of skin filariae. Their active dispersal is usually short and limited (< 500 m), but passive dispersal through wind can spread populations over large areas. Little is known about their natural longevity; Culicoides obsoletus live more than 50 days in captivity, but one month seems to be their average longevity. Adults are captured using animal-baited traps or by black light traps. The nuisance or damage of biting midges is due to their occurrence in large numbers, which affects tourism, forestry or farming (e.g. as many as 10 000 Culicoides nubeculosus per cow have been found in Denmark). The bites of ceratopogonidae are often painful with intense local rash, oedema and pruriginous reactions being able to persist up to three weeks.

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