278 TRESPASSERS UPON THE AIR. 



tubes that penetrate every portion of the body, and 

 often cause great trouble to the dissector. They sur- 

 round and cling to all the internal organs, which they 

 envelope as if in a network of entangling meshes. 



Even in the larvse, which do not fly, this structure 

 is to be found, but it is in the flying insects that it is 

 developed to the highest extent. Not only do these 

 vessels penetrate into every part of the body, even 

 into the delicate antennge and the membranes of the 

 wings, but they are in many parts of the body swollen 

 into large vesicles, which occupy a considerable amount, 

 of space, and materially lighten the body. 



One of the most remarkable instances of these 

 vesicles is to be found in the common Stag Beetle. 



Considering the enormous size of the head and 

 mandibles in a fully developed male, it would be 

 'natural to suppose that even if the insect were able to 

 raise itself in the air at all, it would be overbalanced 

 by the weight of the fore part of the body, and must 

 fly with its head downwards. Yet, not only can the 

 insect fly with its head upwards, but I never saw one 

 fly in any other attitude, and as the Stag Beetle swarms 

 in my neighbourhood, I have had plenty of opportuni- 

 ties of watching its habits. 



The large, square head is necessary in order to 

 afford support for the muscles which move the power- 

 ful jaws. Here I may parenthetically remark, that it 

 has been said that the male Stag Beetle does not use its 

 jaws for offensive purposes, and cannot be induced to 

 bite. If that be the case, I can only say that it has 

 bitten me without being induced, for I have frequently 

 received very severe pinches from the antler-like jaws. 



