Diptera Ephemeroptera

DIPTERA Introduction

Flies are one of the most recognized pests in the urban environment. The fore wings of dipterans are developed, but the hind wings are reduced to small knobbed structures called halteres. Adult flies are active during the day, sometimes at dawn or dusk, and are usually attracted to the odors from sites suitable for larval feeding and development. The larvae are known as maggots, and although this is the primary feeding stage, it is often in a different habitat from the one visited by adults.

Domestic and peridomestic habitats attract fly species that feed as adults or larvae on decaying organic material. Many of these species came from populations in natural habitats separate from the urban environment. Food storage indoors often results in small amounts of ripe and decaying substrate that attractadultflies. Female fungus gnats and fruitflies can detect alcohols, acetic acid, and other volatile compounds from these materials, and follow the odor to an oviposition site. Dead and decaying organic matter is quickly identified as an oviposition site by adult scatopsides, sepsides, and phorids. Adults of several fly species are found indoors in the fall and winter. These include overwintering cluster flies and face flies that spend the winter in attics, wall voids, and other rooms. Chlorpoids and other small flies that occur in large numbers at windows in the fall do not overwinter, butare gathered in large numbers by prevailing winds and are carried in through open windows. Female mosquitoes use building basements and other protected sites to spend the winter, emerging sometimes to take a blood meal.

Peridomestic habitats and their organic substrates attract flies from populations in natural or undisturbed areas. Primitive families, such as the midges, chironomids, and bibionids, utilize wet organic matter as a breeding habitat, and sites with this substrate can be found scattered in urban environments. A large number of mosquitoes have adapted to breeding in standing water collected by domestic containers outside urban buildings. The original habitats for some species offlies have disappeared, or they have been abandoned in favor of artificial sites. Muscids, and blue and green bottle flies utilize the predictable presence of decaying garbage, carrion, and feces from domestic dogs and cats in urban environments.

Mouthparts of the adults are variable. Most species have sucking mouthparts; some blood-feeding groups have what can be considered as a piercing-sucking or piercing-lapping arrangement. In others the adults feed by sponging and lapping liquids from surfaces. In some of the primitive and advanced flies the mouthparts are nonfunctional, and the adults may live a short time. The immatures are the primary feeding stage for most species and usually have well-developed chewing mouthparts.

Eggs are usually deposited directly on the food source of the immature stages; the females of some species deposit live larvae. Hatching usually occurs in 1-3 days, and larval development is completed in 1-3 weeks. Larvae generally utilize a temporary food source, and complete development while conditions remain suitable. Larvae are generally legless and in most groups they are somewhat wormlike. The immature stages of some of the aquatic families, such as mosquitoes and blackflies, are unusual. In the primitive families of flies the larval head is well developed, usually sclerotized, and the mandibles move laterally. In the higher flies the head of the maggot is not sclerotized and indistinct, and the mandibles or mouthhooks are internal and move vertically. The mouth-hooks in higher flies are accompanied by largemuscles and they can be used effectively to scrape food into the mouth, and in some species they aid in locomotion, on a substrate or through the air.

There are usually four larval instars, but in higher flies the last instar is indistinct and completed within the puparium. The pupal stage of the primitive flies is exposed, but in the higher flies the pupal stage is passed in the last larval skin, the puparium. Full-grown larvae usually move a short distance away from their food substrate to molt and form the puparium, a process called pupariation (butinaccurately called pupation). The fourth instar is nonfeeding and within about 24 h molts to the pupal stage. The adult emerges from the puparium through the anterior end.

Pest status may be restricted to one stage or shared by both the adult and maggots. Mosquitoes, black flies, and deer flies are pests by their feeding habits, and their ability to transmit disease organisms. Other species are pests merely by their presence indoors or outdoors. Species in domestic habitats are associated with decaying plant or animal material, and the larvae are saprophagous. Pest status of a few species is based on their presence in large numbers, such as overwintering cluster flies, face flies, or lovebugs swarming over roads and around buildings. Species inhabiting peridomestic habitats also achieve pest status by large numbers, as a nuisance or because of the blood-feeding habits of females.

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