FLIES. 407 



the so-called puparium. The pupae may be very active, but in all such cases the motion 

 is produced by movements of the abdomen alone, and by these means the insects find 

 their way out of the earth, or are adapted for a free aquatic life. Those that are 

 inactive are chiefly those contained in the lai-val envelope, the larvae pupigerae. 



In Europe over nine thousand species of flies are known, and altogether there have 

 been described nearly twenty-live thousand. From North America nearly four thou- 

 sand names have been given. 



As very many species are small and inconspicuous, and not a few minute, it is 

 certain that in Europe, where they are best studied, there are many yet to be found. 

 As evidence of this it is only necessary to mention that not many years ago Winnertz 

 described as new nearly one hundred and fifty species of the single genus Sciara 

 from Europe. At least seventy-five, and probably one hundred thousand species, 

 seems to be a fair estimate of this order occurring throughout the world. In their 

 geographical distribution they show few striking points of interest ; there are compara- 

 tively few genera peculiar to any one continent, and many species are widely dis- 

 tributed, some indeed almost the whole world over. They are found in all portions 

 of the earth where man has ever been, though they flourish best where vegetation 

 most abounds. In geological distribution they do not extend very far back in time, 

 the first reliable remains occurring in the Jurassic beds of Solenhofen. In the tertiary 

 times, however, remains of the order are found in large quantities ; in North America 

 many have been described by Scudder from the Rocky Mountain deposits. Wherever 

 they are found they show but little variation from the types now living. 



As a rule flies prefer the bright sunshine, or sunshiny weather, disappearing from 

 view in cloudy days and at night-time. Some, however, like the mosquitoes and their 

 allies, fly mostly at night. Their habits vary much ; the larger number live about 

 flowers, feeding upon pollen and honey ; whole families, however, are carnivorous, liv- 

 ing upon the juices of other insects or of vertebrate animals. As a whole, the oi-der 

 is a beneficial one to the human economy. While we may resent the impertinent 

 mosquito's and the troublesome housefly's molestations, and while the black-fly and 

 horse-fly may cause the death of many horses and cattle, yet the larger number 

 are purely parasitic in their habits, either in the larval or adult states, upon other and 

 usually injurious insects. Many others, too, act as beneficial scavengers of unwhole- 

 some matters, which would otherwise often bring disease and death. 



SUB-ORDER I. - - ORTHORHAPHA. 



In this division the pupae escape from the larval skin through a T-shaped orifice, 

 or rarely through a transverse rent between the seventh and eighth abdominal rings. 

 Pupae chiefly free. Adults wholly without a lunula above the antennae. 



SECTION I. NEMATOCERA. 



Antennae usually many-jointed, the joints, except the basal two, alike, often 

 fringed with hairs or bristles ; palpi often four or five-jointed and elongated. 



The family MYCETOPHILID.E, commonly called Fungus Gnats, in which the species 

 are usually small or minute, comprises about seven hundred described species, and prob- 

 ably several times as many in reality. The larvae live chiefly in fungi and decaying 

 wood or other vegetable matter. They are usually elongate and cylindrical, bare, with a 



