10 STRUCTURE OF CERTAIlSr DIPTEROUS LARViE. 



these there are the fruit-flies, whose larvae hve in apples, cherries, 

 gooseberries, and oranges, and the pomace-flies that hover around 

 grapes, pears, and other fruits. 



There are also other Diptera wliich do not occur m the intesti- 

 nal canal, but which may deposit eggs in wounds, or m the nose 

 or ears. The screw-worm is a notable insect of this class, and each 

 year one or more cases reach the bureau of this species afi"ecting 

 the nose or ears. The larva of the ox warble or bot-fly (Fli/poderma 

 lineata Villers) also sometimes occurs in man. The eggs of this 

 species are deposited upon the hairs of cattle and licked off by the 

 animal, develop m the stomach, and the larvae bore upward to the 

 back, there to cause the "warble." If some of these eggs drop into 

 the milk pail there is a chance that they wHll be swallowed by a per- 

 son. So there are various cases recorded, mostly of children, where, 

 in the winter time, a larva is observed under the skin, usually in the 

 neck or shoulders, and upon removal proves to be the larva of the 

 bot-fly in its second stage. 



Many of the muscid and sarcophagid larvse deposit eggs or larvae 

 upon dead animals. Although these animals are usually too far along 

 in decomposition to serve as food, yet in some cases these eggs are 

 deposited in time to be taken when the flesh is eaten. In most cases, 

 however, such flesh is cooked enough to kill the contained maggots. 



The larvae of the Muscidae often occur m manure as well as on decay- 

 ing vegetable and animal matter. Prof. Portchinski, of Russia, has 

 studied a number of Russian species of these coprophagous and 

 necrophagous Diptera, and his several papers are the most valuable 

 heretofore produced upon them. Unfortunately for us these papers 

 are published in the Russian language. The late Baron von Osten 

 Sacken gave a summary of one of them in English; and of another, 

 most valuable from the systematic point, the writer has been able to 

 secure a translation of several portions. In this paper ^ he gives 

 descriptions of the larvae, as well as their habits, and tells how to dis- 

 tinguish the allied forms. He has used several of the characters 

 which will be used in tliis paper, especially the posterior stigmata and 

 the anal tubercle. He has not touched on the fruit-flies, however, 

 nor has he given any generalizations for the separation of the larvae 

 of the various families. 



Several other naturalists have studied individual species of the 

 Muscidae or Sarcophagid ae, and in some cases published extremely 

 valuable papers upon them. Thus Lowne has worked up the blowfly, 

 Hewitt the house fly, Blanchard the screw-worm, Portcliinski the 

 Sarcophila wohlfalirti, and Newstead the stable fly. In the Annales 



' Biologie des raouches coprophagues et necrophagues. <Hor. Soc. Ent. Ross., vol. 26, pp. 63-131. 1891. 



