INSECT LIFE IN INDIA AND HOW TO STUDY IT. 167 



largest part of the animals of the world ; they outnumber in species 

 all the other terrestrial animals together ; whilst compared with 

 the vertebrates their numbers are simply enormous. It is perhaps 

 owing to their size that they have been so little studied as a Class 

 and that so little is known as to the number of species at the present 

 moment living upon the earth's surface and of the habits of the 

 greater number of the known species. The largest Insects scarcely 

 exceed in bulk a mouse amongst mammals or a wren amongst 

 birds, while the smallest are almost or quite imperceptible to the 

 naked eye, and yet the larger part of the Animal matter existing 

 on the lands of the globe is probably contained in the forms of 

 Insects. 



In the waters of the globe the predominance of Insect Life 

 disappears. They practically only exist in any numbers in small 

 collections of fresh water, and then it may be for only a portion 

 of their existence ; of the larger bodies of fresh water they 

 invade the fringes only, and they are almost absent from the oceans. 



Insects may be said to be the most successful of all animals in the 

 struggle for existence, and this is probably due to the rapidity of 

 their growth owing to the peculiar relations which exist between the 

 great functions of circulation and respiration, these being of such a 

 nature as to enable the nutrition of the organs of the body to be 

 carried on rapidly and efficiently so long as a certain bulk is not 

 exceeded. 



Rapidity of growth is in the case of some Insects very great and 

 the powers of multiplication even greater still. In addition, by a 

 process known as a metamorphosis," growth and development can 

 be isolated from one another, thus allowing the former to go on 

 unchecked and uncomplicated by the latter. It was probably in 

 allusion to some of these favourable features of Insect Life and the 

 remarkable rate at which they sometimes multiply that Linnseus 

 made the statement, 



Tres muscae consumunt cadaver equi^ aeque cito ac ho, 

 not at all an improbable contingency, since it has been calculated that 

 one female of the common house fly, Musca domestica, may have 

 25,000,000 descendants during one season. 



I have said that by a process of metamorphosis growth and develop- 

 ment are isolated from one another, and thus we get the different 



