The Two-winged Flies 
3°3 
ing and injurious pests of horses, cattle, rabbits, rats, etc.; the fierce robber- 
flies that prey on other insects, including their own fly cousins; the midges 
and gnats, that gather in dancing swarms over pastures and streams; the 
black-flies and punkies, dreaded enemies of the trout-fisher and camper; 
and, worst of all, the cosmopolitian mosquito, probably the most serious insect 
enemy of mankind. Only in recent years have we come to recognize the 
mosquito’s real capacity for mischief. Annoying and vexatious they have 
always everywhere been, by day and night, from tropics to pole, from the 
salt marshes by the sea to the alpine lakes on the shoulders of the mountain- 
peaks. But that the mosquito-bite not only annoys but may kill, by infect¬ 
ing the punctured tissues with the germs of malaria or yellow fever or filari- 
asis, three of the most wide-spread and fatal diseases of man—this alarming 
fact is a matter which has come to be really recognized only recently, and 
the general recognition of which has given to the practical study of insects 
an importance which years of warning and protesting by economic entomol¬ 
ogists have been wholly unable to do. 
The Diptera include about 7,000 known species in North America, thus 
ranking among the principal orders of insects in degree of numerical represen¬ 
tation in this country. About 50,000 species are known in the whole world. 
The order may be separated into certain principal subdivisions by the 
following table: 
Living as external parasites on mammals, birds, or honey-bees; body flattened and 
often wingless; the young born alive as larvae nearly ready to pupate. 
Suborder Pupipara (see p. 351). 
Not living on the bodies of other animals; young usually produced as eggs. 
Suborder Diptera genuina (see p. 304). 
Antennae with numerous (more than five) segments. .Section Nematocera (see p. 304). 
Antennae with not more than five segments, usually with three, the third sometimes annu- 
lated, showing it to be a compound segment, i.e., composed of several coalesced 
segments..Section Brachycera (see p. 327). 
Third segment of antennae annulated, showing it to be composed of several coalesced 
segments. (see p. 327). 
Antennae consisting of four or five distinct segments.(see p. 330). 
Antennae with but three segments (rarely less), the third segment with or without a 
style or bristle.(see p. 332). 
Of the two suborders the smaller one, the Pupipara, including certain 
strangely specialized and degraded parasitic flies, will be considered last. Of 
he first suborder, the Diptera genuina, the various families of small midge- 
and mosquito-like flies composing the section Nematocera (flies with slender 
several-segmented antennae) will be discussed first, as they are believed by 
entomologists to be the more generalized or simpler flies. 
