HYDROPHIL. Q7 
Common error, and ascertained the real structure 
of the animal, which 'he has clearly and satis^ 
factorily explained. 
The larvm of the Hydrophils are supposed to 
remain about two years before they change into 
pupm or chrysalides. When the larva is arrived 
at its full growth, it secretes itself in the bank of 
the water it inhabits, and having formed a con- 
venient cavity or cell, lies dormant for some time, 
after which it divests itself of its skin, and appears 
in the form of a chrysalis, in which state having 
continued for some time longer, it again delivers 
itself from its exuvirn, and appears in its complete 
or beetle form. When first disengaged from the 
skin of the chrysalis, it is of a pale colour, and 
very tender ; but in the space of a few hours the 
elytra or wing-cases acquire a degree of strength 
and colour, which gradually grows more and more 
intense, till the animal, finding itself sufficiently 
strong, comes forth from its retreat, and commits 
itself in its new form to the waters. 
The male is distinguished from the female by 
the structure of the fore-legs, which, as in the genus 
Dytiscus, are furnished, near the setting on of the 
feet, with a sort of horny, concave flap or shield ; 
tlie legs of the females being destitute of this part. 
The structure of the hind-legs is finely calculated 
for the animal’s aquatic mode of life, being fur- 
nished on the inside with a series of close-set 
filaments, so as to give a sort of finny appearance 
to the legs, and to enable the animal to swim with 
the greatest ease and celerity. It may be added, 
' V. VI. p. I. 7 
