1878. | On the Transformations of the Red Mites. 145 
trated by a brief reference to a common red water mite (Hy- 
drachna belostome Riley) which we have studied. The mites of 
the typical genus Hydrachua are, in reality, the aquatic repre- 
sentatives of Zrombidium, and have a precisely similar mode of 
development. We have not had the eggs, but in Europe they are 
known to be laid in spring, in holes in soft-stemmed aquatic 
plants. 
The young larva (Fig. 60) like that of Zroméidium, is pale red, 
hexapodous, and with the legs 6-jointed, including the coxal 
joint. It has the mouth-parts retracted, and is characterized by 
two dark eye-spots anteriorly, and by the swollen second joint of 
Fig. 6. pes belostomæ; 6, newly hatched larva ; æ, larva soon after becom- 
ing fixed; c, mature ep with pupa forming within ; 2 adult ; e, its pedal claws; 
J, palpal claws sf lar 
the palpi PEE at each anterior corner. Moving about in the 
water these young larvæ fasten, often in very large numbers, to 
different aquatic insects. Water bugs of the family Belostomidæ 
-are particularly subject to attack, and especially Zattha fluminea 
(Say'), upon a single specimen of which we have sometimes 
counted over too. They are able to fasten to the bug by means 
of several sharp hooks at the end of the palpi. Once fixed, the 
head and mouth parts stretch until they become separated by a 
neck from the main body, the transparent skin of which rapidly 
=“ swells and elongates so as to form a bag with the more solid, 
dark-red parts visible anteriorly. (Fig. 6a.) The maxilla pene- 
trate and extend beneath the chitinous covering of the host, until 
they form a long pointed thread. ` The legs curl up, become use- 
less, and are more or less withdrawn, and the larva gradually 
7 z passes to the pupa state within this bag, which becomes more and 
: = more swollen and rounded posteriorly, and finally bursts to 
_ release the adult mite. This bag-like larva was looked upon as 
os Perthostoma aurantiaca, Leidy. 
