444 TRANSFORMATIONS OF INSECTS. 



metamorphosis, for it has to undergo a moult and a structural 

 change, which, however, is not of great magnitude. These little 

 oval pear-shaped HydracJincB are not capable of reproducing their 

 kind, so they live a life of childhood for a while, and then after the 

 lapse of several weeks, their growth having been considerable, they 

 settle down upon a potamogeton leaf, and stick their beaks into its 

 cellular tissues, and hang on by their legs. This anchoring and 

 sticking in of the beak is not done for the reception of food, but 

 is otherwise a direct imitation of the procedure of the larva which 

 did the same to the water beetle. In a short time the soft parts 

 of the legs are seen to retract, just as they did in the nymph, and 

 to leave the outside skin, which still adheres to the plant, and to 

 collect en masse in the body. There they undergo a second 

 elaboration ; they assume gradually the shape of the limbs of the 

 perfect HydracJma, elongate, become thin, and harden little by 

 little. The hairs and all the details of the future skin form within 

 the old skin, which finally cracks and gives passage to the perfect 

 Hydrachna, which swims off to lead a life of courtship and maternal 

 care after its wonderful evolution. 



The skin left behind is very curious, for it is really the covering 

 of the former legs, jaws, eyes, and body. Duges managed to cut 

 off one or two legs from some HydracJincs before they began to moult 

 in the last stage of their existence, and he found that the mutilation 

 was not cured during the moult, or rather the fourth metamor- 

 phosis, for the limbs came out truncated and conical in shape. 



The common red spider of hothouses and gardens makes a 

 delicate web on the under surface of leaves, and sticks its sucker 

 into them when thus protected, and lives upon the vegetable juices. 

 Its history is not known, but another kind, belonging to the same 

 division of the spiders without segments on the abdomen, leads the 

 same kind of life and undergoes metamorphosis, 



Scheuten described* Typhlodroimis pyri, one of the Ganiasci 

 which lives upon the leaves of the common pear tree. The mature 

 spider is blind, yet it keeps in very rapid motion ; and the larva is 

 also eyeless, but the front pair of legs appear to replace the organs 

 of sight to a certain extent, for they are kept in constant motion, 



♦ "Ann. Mag. Nat. Hist." 1S57. 



