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HUNGERFORD: AQUATIC HEMIPTERA. 197 
of the male possess on the inner faces of the femora and tibie peculiar 
stridular areas. 
The tibial structure is borne on the inner face of a prominence, which 
is formed by the elevation of the inner angle or margin of the tibia n ar 
its kase into a thin but elongate spur. This spur is lacking in the 
female, and not discovered in the nymphs. (See pl. XXIV, figs. 5 and 6.) 
The Development Changes 
Head. The notocephalic margins of the eyes, which are near together 
and nearly parallel in the adult, are relatively much farther apart in 
the first instar nymph. In the newly hatched bug, the distance at syn- 
thlipsis is nearly 144 width of the head, with the margins of the eyes 
diverging broadly to the vertex. As the development proceeds from in- 
star to instar the eyes are brought nearer and nearer to their relations 
in the adult where the synthlipsis is reduced to about 7.14 per cent of 
the width of the head. 
The beak is 4-segmented and the antennz of the ata have much 
the form of those in the adults. 
Legs. The general form as in the adult. The tarsi of all legs 1-seg- 
mented and terminated by two claws. (The tarsi of the adults are 
2-segmented and end in two claws.) 
Wings. The wing-pads are very conspicuous even in the later nymphal 
instars. By the third instar the pads appear on the antero-ventral mar- 
gins of the mesothorax as little flaps, the distal ends of which reach a 
position on a line with the trochanter of the fore leg when flexed. In 
the fourth instar they are much larger, the apices attaining to a 
position on a line with the distal end of the mesothoracic tibiz when 
the limb is flexed. In the fifth instar they are still closely applied to 
the side of the thorax, but the tips of the more opaque pads reach a 
point on a line with the distal ends of the hind coxe. 
Habits of the Species. Buenoa margaritacea is the common repre- 
sentative of its genus in the ponds and pools of eastern Kansas. It ap- 
pears to prefer the open water and is in much better equilibrium in 
its watery world than the Notovecte. 
Individuals of this species may be seen in large numbers swimming 
slowly or even poising in mid-water some distance beneath the surface. 
They abound in waters teeming with Entomostraca, upon which they 
largely feed, the crib formed by the closure of the anterior two spiny 
pairs of legs being nicely adapted to the retention of such prey. Their 
dexterity in the manipulation of this device and its efficiency in retaining 
small teings may be demonstrated quite readily under the binocular, 
and affords another of nature’s illustrations of the fitness of form to 
function. 
Like others of the predatory ciass of water bugs, thev do, on occasion, 
fall upon Corixids and other forms than the Entomostraca, but not with 
the regularity of many of the others. 
Adults appear from early spring to late fall. The eggs may be found 
in May, the nymphs begin to emerge by the middle of the month, and 
