Order DIPTERA 
Flies 
The Diptera constitute one of the largest orders of insects. The 
majority of species differ from other insects to which the term 
“fly” is applied, such as the sawflies, stone flies, and dragonflies, 
by the fact that they possess only one pair of wings, the fore- 
wings. Their hindwings are reduced to small knobbed structures 
called halteres. The majority of species are soft-bodied and small 
to minute in size. The larvae, commonly known as maggots, are 
legless and vary in form from slender and elongate to stout and 
cylindrical. The pupae may be free, loosely enclosed, or held im- 
mobile in the last larval skin. In the latter case it is known as a 
puparium. 
Many species of Diptera are destructive pests and are of great 
economic importance. Blood-sucking forms such as the mosquitoes, 
black flies, punkies, horse flies, and others are serious pests of 
man and animals. Some of these as well as some of the scavanger 
species, such as the house fly, are important vectors of the causa- 
tive organisms of such serious diseases as malaria, yellow fever, 
filariasis, dengue, sleeping sickness, and dysentery. A number of 
others are important pests of agricultural crops; a few are pests 
of trees and ornamental plants; and many are important parasites 
or predators of injurious species of insects. 
Several native and introduced species are highly effective para- 
sites of some of our most destructive tree-defoliating insects, espe- 
cially of the order Lepidoptera. A few aquatic species, some of 
which are nuisance pests in the adult stage are economically im- 
portant as fish food in the larval stage. 
Several comprehensive treatments of the order Diptera have 
been published. Curran’s revision (181) of Williston’s Manual 
(769) is especially useful in the classification of adults. Brues, 
Melander and Carpenter (114) published a key to families. Stone, | 
et al (695) issued a catalog of the species occurring in North 
America north of Mexico. 
Family CULICIDAE 
MOSQUITOES 
Mosquitoes are important pests of man and animals. Not only 
are their bites extremely annoying, but they transmit many of the 
most serious diseases of man and animals, such as malaria, 
dengue, yellow fever, and encephalitis. As nuisances, they often 
seriously interfere with public enjoyment of parks, vacation sites, 
and other recreational areas. Woods workers, fishermen, hunters, 
vacationers, and hikers are also hounded by them. The health of 
domestic animals and wildlife suffers with serious losses of 
weight and disease. 
A total of 22 genera and 117 species of true mosquitoes occur in 
the United States and Canada. (693). The larvae and pupae live 
in standing or slowly moving bodies of water that range in size 
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