LIFE-HISTORY OF THE LOCUST MITE. 



313 



The youDg larva (Fig. 44, &,), like that of Tromhidium, is pale red, hexa- 

 podous, and with the legs 6-jointed, includiug the coxal joint. It has the 

 mouth-parts retracted, aud is characterized by two dark eye-spots aute- 



Fig. 44.— Hydeachxa belostom^.— b, newly hatched larva ; a, larva soon after • 



becoming fixed; c, mature larva with pupa forming within; d, adult; e, its 

 pedal claws;/, palpal claws of larva. (After Kiley.) 



riorly, and by the swollen second joint of the palpi showing at each 

 anterior corner. Moving about in the water, these young larvae fasten, 

 often in very large numbers, to different aquatic Insects. Water- 

 bugs of the family Belostomidce are particularly subject to attack, and 

 especially ZaUha fluminea (Say),'^* upon a single specimen of which we 

 have sometimes counted over 500. They are able to fasten to the bug 

 by means of several ^arp hooks at tlie 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 elon- 

 gates so as to form a bag, with the more solid, dark red parts visible an- 

 teriorly (Fig. 44, a). The maxillae penetrate and extend beneath the 

 chitinous covering of the host, until they form a long, pointed thread. 

 The legs curl up, become useless, and are more or less withdrawn, and 

 the larva gradually passes to the pupa state within this bag, which be- 

 comes more and more swollen and rounded posteriorly, and finally bursts 

 to release the adult mite. This bag-like larva was looked upon as an Qgg 

 by many old authors, and was made the type of the genus Aclilysia by 

 Audouin. The adult swims actively about in the water, but before 

 attaining maturity fixes to some plant, and undergoes another molt 

 without material change of form. 



Hydrachna belostom^ Riley. — Larva. — Hexopodous. Elliptic-ovoid. Pale red, 

 with two dusky eye-spots. Legs 6-jointed, includiug cox£e ; terminal joint longest ; 

 claws very small. Surface closely and evenly studded with minute points. Palpi 

 drawn beneath the head, with the second joint greatly swollen, and showing like an 

 eye at each anterior side of the body ; the three terminal joints indistinctly separated, 

 and each armed with a sharp hook. Becoming elongate and more or less pyriform, 

 •with a distinct neck when fixed. 



Papa formed within the bag-like body of larva. 



Adult. — Average length when first from pupa 1.5 mm.; globular; color dark blood- 

 brown ; body smooth ; legs with but few hairs, terminal joint truncate aud with two 

 very minute claws ; palpal claws very small and the thumb no longer. ' 



Ground-beetles. — We have seen that in the larva state several of 

 these insects attack locust-eggs. The perfect beetles are among the 



^*=:Perthostoma aurantiaca Leidy. 



