ENTOMOLOGY IN OUTLINE DIPTER A. 85 



produced alive, and, in other cases even, the female gives birth to the 

 young in the pupa form. As a rule, however, there are the usual well- 

 defined periods of the insect life. With many of the flies, as in the case 

 of meat-flies, the eggs hatch very soon after deposition, and the in- 

 sect passes through all its changes in a very short time. In this we 

 see a wise provision of nature, which arranges that the fly shall pass 

 through its young stage and reach perfection while its food is available. 

 If it were to remain long in its larval stage, its food supply would 

 putrefy, and dry up before the insect matured, and the young fly would 

 die of starvation. 



Flies are adapted to various conditions, and breecl under all circum- 

 stances. Some are aquatic, as the mosquitoes; some subterranean, as 

 the crane-flies. Many breed in dirt and filth, and some swarm in 

 cesspools, as the rat-tailed larva? the young of a Syrphus fly and we 

 have seen masses of maggots crawling in the crude oil running from 

 the wells, and apparently well satisfied with conditions which would 

 have knocked out any other form of insect life. 



One of the most terrible of the dipterous pests is the so-called screw- 

 worm (Compsomyia macellaria) . This is a common species throughout 

 a large portion of our country, and ordinarily feeds upon dead or 

 decaying vegetable matter. Under some circumstances, however, it 

 attacks living animals, and in the Southern and Southwestern states 

 occasionally becomes a terrible pest. On such occasions it lays its eggs 

 on man or animals wherever there is the slightest trace of a wound, 

 bruise, or offensive discharge of any kind. The larva? bore directly 

 into the living flesh, causing intense pain as well as suppurating sores. 

 Living larvae are produced, as well as eggs almost ready to hatch, and 

 in any opening from which there is a discharge of any kind eggs may 

 be deposited. Sleeping humans with an offensive breath, or with a 

 fetid discharge from the nostrils or mouth, have had eggs laid at these 

 points, and .larva? have made their way into the head in some cases, 

 causing the death of the individual. Eggs have also been laid in the 

 far- of uncleanly people, and the channels and passages of these organs 

 have been penetrated into the head and destroyed. Animals are 

 troubled in the same way. and where the insects are abundant their 

 attacks often become fatal. The following, which appeared in a San 

 Bernardino paper several years ago, gives a very vivid account of the 

 work of this dreaded insect: "George Madden, a Western Union Tele- 

 graph lineman, was brought to the county hospital from the desert 

 afflicted with a most loathsome complaint, actually being eaten up 

 alive by thousands of minute worms which have hatched from the eggs 

 laid in his nostrils while he was asleep. A description of his condition 

 is too revolting to be printable. Madden states that three weeks ago 

 he was employed by the telegraph company at Los Angeles and was 



