MICROSCOPIC DRAWING AND ENGRAVING. 



description, are placed in the membraneous paddles along its sides, 

 and the air is imbibed from the surrounding fluid. 



56. After this creature has remained for a considerable time in 

 the state of larva, and when it appears to become conscious that 

 the epoch of its passage into the second stage of its existence, that 

 of chrysalis, is approaching, it issues from the water and proceeds 

 to excavate for itself a hole in the ground, in which it undergoes 

 the metamorphosis by which it passes into the state of a chrysalis, 

 in which it remains for some days, after which it emerges a per- 

 fect beetle. 



The female bears on each side of the hinder extremity of her 

 body a spinning apparatus, which she uses to make the bag in 

 which her eggs are deposited, and which has been already 

 described. 



57. Dr. Groring has also left a drawing of another species of 

 dytiscus, called the water-beetle. 



This insect resembles, in the manner of its propagation and its 

 habits, that which has been above described. It is carnivorous, 

 and of a ferocious and cruel character. If it is placed in a vessel 

 with other aquatic insects, it soon devours them. 



A magnified view of it is shown in fig. 35 ; the insect, in its real 

 size, being represented in the lower figure. The drawing from which 

 this engraving was taken, was made immediately after it had cast 

 its first skin, a moment at which its internal organisation is more 

 distinctly visible than at any other period of its existence, by 

 reason of the thinness and transparency of its newly-developed 

 vessels. Its anatomical structure is more delicate and beautiful 

 than that of any other larva of the order of coleoptera, and, 

 although its weapons of attack appear less formidable than those 

 of the water-devil and some other species, the remarkable manner 

 in which its internal functions are rendered visible more than 

 compensate for this, when the insect is regarded merely as a 

 microscopic object. 



It is armed with a pair of curved mandibles, which move 

 horizontally, and are long enough to cross each other when 

 closed. They are of a fine nut colour, becoming darker towards 

 the points, which are hard and sharp. With these the insect 

 seizes its prey, and bringing it towards its mouth, sucks its blood 

 after having first pierced it. This it delights to do without 

 killing its victim, unless it is constrained to do so, by the superior 

 strength of the latter. If it seizes the larva of the gnat, or any 

 other tender insect, it brings different parts of its body to its 

 mouth, devouring it piecemeal, except the skin, which it rejects. 

 If *its prey is a strong animal, protected by an external shell, it 

 seizes it, and holds it for some time at rest, until its victim 

 86 



