CREOPHILA. 97 



at the posterior pole of the egg. The chorion and vitellftie mem- 

 brane adhere to each other quite firmly at particular places, more 

 especially about the true micropyle, so that the openings pass 

 through both membranes. The micropyle of the bluebottle flies 

 gives us the clearest insight into the penetration of the seminal 

 filaments into the egg, and it is particularly to be recommended 

 for the study of this process. It occurs at the superior pole of the 

 egg, which is rendered as uneven as the rest of the chorion by 

 facets and pores, and in its centre. The albuminous mass of the 

 egg covers the micropyle and the superior pole. The eggs are 

 usually laid in this state, but sometimes the larva has already 

 become completely developed in the egg, so that it is frequently 

 excluded whilst being examined under the microscope, whence 

 arises the supposition that the eggs are hatched in two hours. 

 The larva bears two blackish-brown points at the extremity of 

 its abdomen, and has a very complicated oral extremity ; its mar- 

 gin is divided in a radiate form, and it has six spiracles on the 

 abdomen. In eight days it attains its normal size without 

 changing its skin, and becomes converted into a cask-shaped 

 pupa by mere thickening of the skin ; from this the fly escapes 

 in a few days. The fertility of this fly is so great, that 

 Reaumur counted 20,000 maggots in an oviduct 2" long. The 

 larvas of this fly cause the so-called " living wounds " to which 

 Pruner, for example, refers. They especially prefer the orbits 

 and ears, but also every part of the body where there is the 

 least abrasion or discharge. To the naked eye such places 

 appear as if beset with headless nails, which rise and fall with 

 the extension and contraction of the animals whilst sucking. 

 Pruner thinks that in such wounds we have to do with the Iarva3 

 of Sarcophaga carnaria ; I have arranged them here on account of 

 the black points on the abdomen. In ulceration, and when their 

 position is superficial, we distinctly see the white body of the 

 larva, which is 2'" in thickness ; the head sits, with its booklets, 

 in the bottom of the wound, which usually secretes no pus, but 

 only a bloody, watery fluid, and has a bluish, pale, and after the 

 removal of the animals a favus-like, spongy appearance. The 

 black hinder parts and the respiratory orifices are directed 

 outwards. 



Treatment. The best is the careful removal of the animals 

 with the forceps. Enticing them out with milk does not suc- 

 ceed, according to Pruner ; touching them with a weak infusion 



7 



