632 INSECTS AT HOME. 



much the same manner. When the larva is full-fed, the skin 

 hardens into an oval cocoon, and the pupa is thus developed 

 within its original larval skin. 



To this enormous group belongs the Blow-Fly or Blue- bottle 

 (Musca vomitoria), which is so very familiar in our houses, and 

 is so apt to deposit its eggs upon meat that even approaches 

 decomposition. Here I may mention that the oval meat-safes, 

 like dish-covers, which are so largely sold for the purpose of 

 keeping the Blow-Flies from the meat, do entirely exclude the 

 Flies, but they do not exclude the eggs, so that the cook who 

 has covered the meat carefully with one of these safes, often 

 iinds that, in spite of her precautions, the meat is as ' fly-blown ' 

 as if it had been totally exposed to the Blue-bottles. The fact 

 is, when the mother insect finds that she cannot gain actual 

 access to the meat, she goes to the top of the cover, and lets 

 her eggs drop through the meshes of the wire gauze. 



Then there is another insect, popularly called the Flesh-Flt 

 or the Baker {Musca or Sarcophaga carnaria), which proceeds 

 in a different and more expeditious way. With the Blue-bottle 

 the eggs have to be hatched after they are deposited, but with 

 the Flesh-Fly they are deposited as maggots, being hatched 

 within the body of the parent. If the female be dissected 

 before she has deposited her young, a most curious spectacle is 

 disclosed. The abdomen is almost entirely filled with two 

 white rolls, like riband, and when these rolls are examined 

 with the microscope, they are seen to consist of a vast number 

 of tiny maggots, placed side by side in perfect order. Each of 

 these rolls contains from eight to ten thousand larvge ; and the 

 reader may easily imagine how rapid is the demolition of the 

 substances on which one of these Flies deposits her multi- 

 tudinous young. 



It was to this species that Linnaeus referred when he wrote 

 the apparent paradox that three Flies could eat an ox as fast as 

 a lion. The Fly does not even wait for decomposition, or at 

 all events can detect incipient decomposition long before it is 

 apparent to the human senses ; for I have often found that if a 

 recently-killed mouse or bird be allowed to lie in any exposed 

 place for an hour or two, vast numbers of these tiny larvae will 

 be deposited upon it, the mother Fly having taken tlie pre- 

 caution to place them under the wings, in the mouth, at the 



