HUNGERFORD: AQUATIC HEMIPTERA. 195 



flexed a splendid crib for the retention of these little animals. Some- 

 times a half dozen or more are detained thus at one time. We have at- 

 tempted to illustrate this device on plate XXIV, showing the limbs open in 

 one drawing and flexed in another. They sometimes attack other insects, 

 such as Corixids, but rely almost exclusively upon the little organisms 

 named. 



Behavior. These insects do not rest at the top as does Notonecta 

 undulata, but may be seen swimming slowly, or even poising in mid- 

 water some distance beneath the surface. They do in fact seem in better 

 equilibrium in the water than the Notonectse. They come to the sur- 

 face and expose the venter of the abdomen by the spreading of the 

 guard hairs, as do the other back-swimmers when in poorly aerated 

 waters. 



The males possess stridular areas upon the inner faces of the femora 

 and tibiae, and also on the sides of the face at the base of the beak. 

 These are shown in the drawings on plate XXIV. The tibial structure 

 is borne on the inner face of a spur near the base of the anterior tibia. 

 When the fore limbs are brought up to the head, it will be seen that 

 the stridular areas of the limbs meet those on the base of the beak. 

 See the figure on plate XXIV. The production of sound is doubtless the 

 purpose of these structures. European workers have recorded Notonec- 

 tids as capable of producing chirping sounds. Miall quotes Redfem 

 to the effect that Notonecta makes a noise like the word "chew" repeated 

 three times. 



The Egg. 



Size 1.125 mm. long by .406 mm. in its widest diameter. The size 

 increases somewhat with the development of the embryo within, which 

 causes a bulging of the stem in which the egg is inserted. 



Shape. The egg is elongate oval when seen in surface view with the 

 cephalic end the more pointed. (Surface view — the side, a portion of 

 which is exposed to view as the egg lies embedded in the stem.) In 

 lateral view it appears nearly straight in the outline of its upper sur- 

 face, while the lower is quite strongly curved. 



Color. Pearly white when first laid — the surface hexagonally reticu- 

 late as in the eggs of Notonecta. A smooth and shiny elongate oval 

 area occupies the anterior half of the upper surface. This is the portion 

 exposed and is margined by a whitish band which marks the union of 

 the egg with the surface of the stem when "in situ." As the embryo 

 develops, the entire egg becomes deep greyish yellow and the red eye 

 spots and other red markings show through the chorion. The part 

 exposed becomes dark amber in color and very shiny in appearance. 

 The surface appears reticulate under magnification. 

 First Instar Nymph 



Size. Body length, 1.85 mm.; body width, .625 mm.; head width, .5 

 mm.; distance between eyes, .156 mm. Fore limb: femur, .25 mm.; 

 tibia, .35 mm.; tarsus, .25 mm. Middle limb: .387 mm., .333 mm., and 

 .275 mm., and hind limb, .625 mm., .630 mm., and .625 mm. for femur, 

 tibia and tarsus respectively. 



