hungerford: aquatic hemiptera. 41 



field, stretches out its raptorial front legs before it, and gives 

 long strong, propulsive strokes with the other two pairs, 

 moved sychronously. ^Vhen not pressed they paddle slowly, 

 alternating the middle and hind legs." 



Of the Notonectidse the little Plea, living midst the tangles 

 of pond vegetation, makes but short excursions from stem to 

 stem by "short little clipping strokes" of its limbs. These 

 limbs on superficial examination appear but slightly fringed 

 with hair, but careful study will reveal them about as delin- 

 eated in figure 2, plate XXM. All their limbs end in strong 

 claws. The other genera, Notonecta and Buenoa, have hind 

 limbs obviously set apart for rowing. They are flattened and 

 bordered with close rows of long hairs. These collapse on the 

 return, spreading with the pressure of the pulling stroke. The 

 tarsal claws of the hind limb are so small that they are scarcely 

 discernible amidst the fringe of swimming hairs. These rear 

 limbs, the height of efl^ciency for propulsion in the water, 

 are suffered to be dragged upon the land, the other limbs 

 already ungainly in their modification for prehension, afford- 

 ing it an awkward means of getting about. 



The greatest diversity of limb structure is undoubtedly 

 possessed by the Corixids. The middle limbs are long, lean 

 structures, ending in long, slightly incurved claws. These 

 are employed only in grappling the irregularities of the bottom 

 of the pool, thus holding their owner to their accustomed 

 foraging grounds. The hind limbs fashioned like those of 

 the back-swimmers, are even quicker in their execution. In- 

 deed no water insect has greater agility and darting propensi- 

 ties than has the water boatmen. 



PREHENSION. 



Kirkaldy once stated that "all of the water forms (with the 

 possible exception of Corixidse) are raptorial." He later modi- 

 fied this to except the Hydrometra, the front legs of which are 

 not thickened, stating that "although doubtless they are em- 

 ployed for holding the food during feeding, they cannot be 

 said to be noticeably modified for raptorial purposes." In 

 fact, the writer has found that Hydrometra habitually spears 

 its prey from beneath the surface film, and retains it by 

 means of the tremendously long, flexible mandibular stylets 

 which are strongly and retrorsely barbed at their tip. (See 

 plate XXIX, fig. 3.) 



