hungerford: aquatic hemiptera. 31 



AAAA. Living within the water — Concluded. 



CC. Swimming in normal position. 



D. Clinging to vegetation or swimming through 

 the water with a steady motion. 



Naucoridse. 



DD. Resting on the bottom, rapid, darting swim- 

 mers. Corixidse. 



PARASITISM. 



Very little has been recorded regarding the parasites of the 

 water bugs. All of them, in all of their active stages, are sub- 

 ject to the attacks of the Hydrachnids. These little water 

 mites attach themselves to the bug and remain until adult, 

 when they molt their last nymphal skin and become free swim- 

 ming. These parasites are often very abundant upon a host, 

 so abundant that they inhibit growth and interfere with the 

 progression of the insect. They are particularly numerous on 

 Ranatra and sometimes disarrange the normal functioning of 

 the caudal air-filaments, as shown in figure 10 on plate XVIII. 

 Corixid nymphs have been noted to show a stunted growth 

 and diificulties in molting, due to the presence of these para- 

 sites. Under the discussion of the biology of the Corixidse is 

 given an account of the seasonal abundance of Hydrachnids. 



According to Kirkaldy, who was a careful student of aquatic 

 Hemiptera, the water mites lay their eggs in spring in in- 

 cisions in soft stemmed aquatic plants or on the underside of 

 leaves. The young larvae are pale red, and possess six legs, 

 each of which is six segmented. They fasten themselves to 

 water insects by means of sharp hooks at the end of their 

 palpi. Once fixed the head and mouth parts stretch until they 

 become separated by a neck from the main body, the transpar- 

 ent skin of which rapidly swells and elongates to form a bag, 

 with the more solid dark red parts visible anteriorly. The 

 elongated maxillse penetrate and extend beneath the chitinous 

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

 The legs curl up and become useless and are more or less with- 

 drawn. The larva gradually passes into the pupa stage within 

 this bag, which becomes more and more swollen and rounded 

 posteriorly, and finally bursts to release the adult eight-legged 

 mite. This swims actively about for a time, but before at- 

 taining maturity fixes to some plant and undergoes another 

 molt without material change of form. Soars, 1901, discusses 



