266 INSECT TRANSFORMATIONS. 



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 dis- 

 play 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 clomL'stica) belongs to the first division, the 

 natural food of its larvaj 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 be 

 primarily directed, rather than having recourse to fly- 

 waters. 



Another common insect (^Bibio Jwrbilanus, Mei- 

 gen) lives in the larva state in cesspools, along with 

 rat-tailed larva3,&c. The maggot of the bibio is very 

 peculiar in form. They are hatched from eggs with 

 shells as hard as Paris plaster, deposited on the adja- 

 cent walls, and frequently upon the pupa case which the 

 mother has previously quitted. Like the larvsp of the 

 crane flies above described, this one moves itself chiefly 

 by means of its mandibles, and therefore it can make na 

 progress on a piece of smooth glass. Its skin, it may 

 be remarked, is so exceedingly hard and tough, that 

 it is no easy matter to kill it.* We have introduced 

 this insect here, however, chiefly for the purpose of 

 refuting an erroneous popular accusation against 

 it, which is supported by the high authorities of 

 Ray and Rt'aumur. Our great English naturalist 

 calls it the deadliest enemy of the flowers in spring, 

 and accuses it of despoiling the gardens and fields of 



* Swauimcidain, x, 212. 



