1889.] 



THE YOUNG NATURALIST. 



85 



much that partook of the character problematical, and which but 

 formed the base for some curious experiments and careful dissections. 



The wings of insects are chiefly intended to serve one purpose in 

 particular, viz. — to assist the creature in migrating from one spot to 

 another in search of food, and to assist in the propagation of its kind. 

 They are utilised for various other minor purposes, such as the 

 creation of sound, a cloak for concealment, and also as an effective 

 shield to ward off the attacks of numerous enemies. To each of these, 

 however, I will again refer in the proper places. 



They serve as great aids to the naturalist in distinguishing the 

 various orders, and also in discriminating between species : for such 

 is their infinite variation, that they form an efficient and almost com- 

 plete key to nomenclature, and all the existing, or I should say, known 

 orders, take their denomination from some prevailing character of 

 wing formation. Westwood classes the insect world into thirteen 

 great divisions or orders, but as we cannot at present deal with those 

 additional features that justify his arrangement, I will take them in 

 such sequence as may be alone indicated by the nature and numbers 

 of the organs of flight. 



The general structure of the wings is very similar thoughout all 

 the orders. They consist of two membranes united at their edges, 

 and traversed by a series of horny rays, which run between them, the 

 upper of which is more strongly attached to them than the lower. 

 These wing-rays or nervures, as we are accustomed to call them, are 

 hollow tubes, convex on the upper surface, flat and of a slighter 

 texture on their underside. 



Entomologists vary very much in their ideas as to the use of the 

 nervures, many being of the opinion that they are vessels for the con- 

 veyance of fluid, others that they are merely air passages. I have 

 devoted some considerable time to a probable solution of the question, 

 and it may perhaps be interesting to place the results before the 

 reader. Both theories are right, but I found certain conditions were 

 necessary to be observed in successfully conducting the necessary 

 experiments, in order to arrive at any definite conclusion. In the 

 first place, the nervures, during the life of the insect are filled with a 

 transparent gelatinous substance, which, as I shall show later on, is 

 the outcome of one of the earliest acts of the creature to provide itself 

 with the special organs forming the subject of my paper. Messrs. 

 Kirby and Spence, in their admirable work, tell us that the nervures 

 contain a spiral thread, and this is readily reconcilable with the 

 assertion of more modern writers, that they are really traversed by 



