224. THE HARMONIES OF NATURE. 



the wasp has contrived for her young ; and as both are produced 

 at the same time, the offspring of the ichneumon not only 

 devour the young wasps, but also the whole supply of larva) 

 which the parent had carefully provided for their support. 



Thus these active flies, which in their perfect state feed 

 solely upon the juices' of flowers, render almost the whole of the 

 insect world tributary to the wants of their larvae ; and as Ger- 

 many alone possesses above 5,000 species of ichneumonidae, 

 it may easily be imagined how terrible they must be to the 

 other insect-tribes, and consequently also how useful to man- 

 kind, by their destruction of myriads, which would otherwise 

 be left to banquet on the fruits of the earth ! The ichneu- 

 mon larvae, thus born in a living body, subsist on the juices of 

 their victim, but without absolutely destroying it in fact, the 

 animal they infest may continue to live for some time, thus 

 affording them a continued supply of nutriment ; but when the 

 ichneumons are ready to undergo their last metamorphosis, they 

 pierce the skin of their now useless victim, and each, spinning 

 itself in a small oval case, changes into a chrysalis the whole 

 number forming a group on the shrivelled body of the unfortu- 

 nate caterpillar. 



The oestri or breeze-flies likewise deposit their eggs in or upon 

 living animals, but instead of choosing, like the ichneumon- 

 flies, other insects for their victims, they ambitiously select 

 large quadrupeds for the future provision of their young each 

 species almost invariably confining its attacks to a certain 

 species of animal. The larvae of the equine breeze-fly, or bot 

 as it is usually termed, can only be developed in the stomach of 

 the horse, and it may well be asked how they are able to reach 

 these hidden pasture-grounds, so indispensable to their exist- 

 ence. But Providence has found the way by teaching the 

 breeze-fly to deposit her eggs on those parts of the horse's body 

 which are most likely to be nibbled by the animal. When the 

 eggs have remained on the hairs four or five days, they become 

 mature, after which time the slightest application of heat and 

 moisture is sufficient to bring forth in an instant the latent larva. 



At this time if the lips or tongue of the horse touch the egg, 

 its operculum is thrown open, and the young larva liberated ; 

 which readily adhering to the moist surface of the tongue, is 

 from thence conveyed with the food to the stomach, when it 



