CHEESE MAGGOTS. 265 



not placed, as in caterpillars, along the sides, but a 

 pair near the head and another pair near the tail. 

 Now, when burrowing in the moist cheese, these 

 would be apt to be obstructed ; but to prevent this, 

 it has the power of bringing over the front pair a 

 fold of the skin, breathing in the meanwhile through 

 the under pair. Well may Swammerdam denomi- 

 nate these contrivances" surprising miracles of God's 

 power and wisdom in this abject creature." 



Like the other destructive insects above men- 

 tioned, the multiplication of the cheese-fly is checked 

 by some insect, whose history, so far as we are 

 aware, is not yet known. Swammerdam found 

 many of the maggots with other larvae in their 

 bodies ; but he did riot trace their transformations. 

 If they were the larvae of an ichneumon, it must be 

 exceedingly minute. 



It must have attracted the attention of the most 

 incurious, to see, during the summer, swarms of flies 

 crowding about the droppings of cattle, so as almost 

 to conceal the nuisance, and presenting instead a 

 display of their shining corslets and twinkling wings. 

 The object of all this busy bustle is to deposit their 

 eggs where their progeny may find abundant food ; 

 and the final cause is obviously both to remove the 

 nuisance and to provide abundant food for birds and 

 other animals, which prey upon flies or their larvae. 

 The same remarks apply with no less force to the 

 blow-flies, which deposit their eggs, and in some cases 

 their young, upon carcases. The common house-fly 

 {Musca domestica) belongs to the first division, the 

 natural food of its larvae being horse-dung ; conse- 

 quently it is always most abundant in houses in the 

 vicinity of stables, cucumber beds, &c., to which, 

 when its numbers become annoying, attention should 



