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 Hydrachn@ 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 ez masse in the body. There they undergo a second 
elaboration ; they assume gradually the shape of the limbs of the 
perfect Hydrachna, 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. Dugés managed to cut 
off one or two legs from some Hydrachne@ 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* Typhlodromus pyri, one of the Gamasez 
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.” 1857. 
