ICHNEUMON. 



her young as might be deposited elsewhere, takes care to lay her 

 eggs on those spots only, such as the knees and shoulders, which 

 the horse is sure to lick ! 



48. Ichneumon was a name given to a certain species of 

 quadrupeds, which were erroneously supposed to deposit their 

 young upon the bodies of crocodiles, the entrails of which they 

 gradually devoured. The name was transferred by Linnaeus to a 

 vast tribe of insects, whose young are destined to feed upon the 

 living bodies of other insects, on which accordingly the mother 

 deposits her eggs. The ichneumons were called by some naturalists 

 Muscce vibrantes, from the constant vibration of_their antenna?, by 

 which they were supposed, in some unknown manner, to acquire a 

 knowledge of the insects which would be fit food for their young. 

 This supposition is, however, clearly erroneous, inasmuch as many 

 species do not manifest this vibratory motion. 



49. The ichneumons are agents of vast importance in the 

 economy of Mature, by checking the too rapid increase of certain 

 species, such as the caterpillars of butterflies and moths, of which 

 they destroy vast numbers. The purpose of nature in this is un- 

 mistakeably manifested by the fact, that the ichneumons increase 

 in proportion to the increase of the species they are destined to 

 destroy. Thus Nature maintains the equilibrium in the organic 

 world as much by the operation of the destructive, as by that of 

 the reproductive principle. 



50. The ichneumon is a four- winged fly (fig. 12), which takes 

 no other food than honey ; and the great object of the female is to 

 discover a proper nidus for her eggs. 



In search of this she is in constant 

 motion. Is the caterpillar of a but- 

 terfly or moth the appropriate food 

 for her young ? You see her alight 

 upon the plants where they are most 

 usually to be met with, run quickly 

 over them, carefully examining every 

 leaf, and having found the unfor- 

 tunate object of her search, inserts 

 her sting into its flesh, and there 

 deposits an egg. In vain her victim, 



as if conscious of its fate, writhes its body, spits out an acid fluid, 

 menaces with its tentacula, or brings into action the other organs 

 of defence with which it is provided. The active ichneumon 

 braves every danger, and does not desist until her courage and 

 address have insured subsistence for one of her future progeny. 

 Perhaps, however, she discovers, by a sense, the existence of 

 which we perceive, though we have no conception of its nature, 



135 



