438 TRANSFORMATIONS OF INSECTS. 
rapidity, with the aid of the iong middle feet, which act like oars. 
The Limnocharis attaches itself in the larval condition to the 
body of the Gerris, selecting the neighbourhood of the head in 
preference to any other spot for its point of attack. This takes 
place before and during the month of July, and then the small 
bright red larve, with great movable suckers, looking like heads, 
may be seen hanging on with their six legs, terminating in strong 
claws. When the larve are fixed they dig their suckers into the 
Gerris, and live at its expense, and are moved about from place 
to place by their restless and unwilling entertainer. Having 
attained at last the size of a pin’s head, the larve detach them- 
selves, and sink down through the water, and crawl over the 
Adult. Larva. 
Hydrachna geographica. (Magnified.) 
weeds and bottom slowly, and seek a hole or a crevice, down 
which they plunge. There the metamorphosis takes place, and 
the six-legged larve become motionless nymphs. The nymph 
stage lasts fifteen days, and then a small brilliant red eight-legged 
adult Limnocharis emerges. 
The globular water mite called Hydrachna geographica may be 
taken as the type of the genus Hydrachna; but M. Duges has 
given such interesting details respecting a closely-allied species, 
FHlydrachna globula (Hermann), that we do not hesitate to take 
advantage of them, especially as they convey most correct impres- 
sions concerning the metamorphosis.* 
The true ydrachne are distinguished by their beaks being as 
* Dugeés, Op. Cit., p. 161 ef seg. 
