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Marvels of the Universe 



similar to that which constitutes the insect's external armour. The\^ are, in fact, 

 in miniature of our wire-lined rubber gas-tubing, and their structure is a 



exact counterparts 

 safeguard against "short 



circuit." The elastic inner coil keeps the tube open even when it is subjected to pressure, as by the 

 bending of a joint through which it passes ; at the same time, the flexibility of the tube is preserved. 

 Now, in the case of the adult Diving Beetle, the breathing-holes do not occupy their normal 

 position along the sides of the body. They open upon the back, beneath the wing-cases. Moreover, 

 the two terminal pairs of breathing-holes are much enlarged, while the wing-cases fit so perfectly 



upon the abdomen that an air-tight space is 

 ^ formed between them and the back of the insect. 



When the Diving Beetle wishes to take 

 breath, it simply poises itself in the water with 

 the hinder part of its body protruding slightly 

 above the surface. It then curves the tip of its 

 abdomen somewhat, when the air rushes into 

 the four big breathing-holes, and fills the space 

 between the wing-cases and the back. The 

 chink is then closed tightly, and the beetle is 

 once more ready for a diving excursion. Ex- 

 periments made by Dr. Sharp, the eminent 

 authority on insect life, revealed the fact that a 

 male Diving Beetle comes to the surface to take 

 breath once in every eight minutes and twenty 

 seconds on an average, and remains poised for 

 about fifty-four seconds. The longest interval 

 that it was observed to pass without breathing 

 was nineteen minutes, although the female 

 insect, being less active in habit, rises less fre- 

 quently than the male. 



We have still to speak of the Diving Beetle's 

 head. Its most important features are the eyes, 

 the mouth, and the feelers. The latter are deli- 

 cate, jointed appendages, which, so far as can be 

 gathered, may be likened to the whiskers of a 

 cat in that they serve the beetle's sense of 

 touch, and are possibly of special service at 

 night, or when the insect is foraging in murky 

 water. The mouth consists of a whole set of 

 useful implements. First, there is the upper 

 lip — a hard plate hinged to the solid armour of 

 the head. Immediately behind this are the jaws, 

 which move sidewise, and not with an up-and- 

 down motion, as is the case with the higher ani- 

 mals. After this comes a second pair of jaws, 

 less powerful than the first, but highly sensitive. 

 Each is made up of several parts, each carries a 

 jointed feeler. So that these secondary jaws are 

 well suited for holding food, examining it, and 

 passing suitable portions towards the gullet. 

 Indeed, they may be likened to a pair of 



Photo by] 



[ll.trnhl n.isiin. 

 THE DIVING BEETLE AND GRUB. 



The appetite of the grub is insatiable; it is always in 

 search of prey. Its flat head is supplied with sickle-shaped 

 jaws, which are traversed by a hollow tube leading to the 

 closed mouth. By this means the blood is sucked out from the 

 victim and goes to nourish the victor. 



