274 NATURAL HISTORY OF ARTHROPODS. 



margin of the membrane. The legs ai-e moderately long, slender, with still more 

 slender three-jointed tarsi, of which the basal joint is minute, and the second joint 

 much the longest. Both pairs of posterior femora, besides the tibiae, are furnished 

 with slender, short spines. The connexivum is wide, curved on the outside, and 

 sharp-edged. 



Our native species, the M. bisignata, is of a pale yellow color, with the gibbous hind 

 lobe of the prothorax lead color, marked with a yellow stripe along the middle, the outer 

 sides and tip of the scutellum, the veins and cuneus of the wing-covers, the eyes, the 

 tylus, the apical joint, points of articulation, base, a few marks on the antennae, a large 

 part of the end of the tarsi, and the tip of the tibiae are brown. It measures only a little 

 more than one-tenth of an inch in length, and tapers to a rounded point behind. The 

 unwinged individuals appear more slender than the winged ones, and often hibernate 

 in this State. On the surface of the quiet waters which they inhabit, specimens may 

 be seen at rest near the banks, or in the midst of the leaves of jDond weeds. There 

 they watch for the arrival of some hasty gnat or other small insect which chances to 

 fall into the water. This they eagerly grasp with the fore-feet and proceed to suck 

 its juices. Theil- movements are indescribably delicate and free. Nothing could be 

 lighter than their motions over the surface, walking there without making impression 

 or ripple, and moving with the celerity of a spider. Thus far it is known from ]^as- 

 sachusetts and most of the States south of it, through Florida to Texas, and thence 

 into Cuba and San Domingo. Its pale colors serve well to conceal it when resting 

 between the leaves of Potamogeton or among other projecting objects upon the sur- 

 face of the water, and it is only by stiri-ing the surface in such places that its presence 

 can readily be detected. 



Two other species appear to belong to this genus, the original one fii-st discovered 

 in France, upon which it was founded, and another from the island of St. Vincent. 

 Very near to this should be placed several more pigmies of the gronj), which deserve 

 notice here as showing the kinds of differentiation which arise within its limits. 



One of these is Hebrus, which is represented in the United States by S. ameri- 

 canus. It is of an oval, somewhat boat-shaped, deej) figure, with a nearly conical head, 

 prominent eyes, antenna about as long as the abdomen, with the second joint a little 

 shorter than the stouter, curved, basal one, the third and fourth more slender, longer 

 than the basal joint, and both about equal in length. The membrane is long, has a 

 discoidal areole of large size, bounded by coarse veins, and a space behind this 

 separated by very slender veins. The prothorax is wide, triangular behind, con- 

 stricted near the head, with prominent tumid shoulders. By reason of this segment 

 being carried back the scutellum is hidden from view. A marked feature of this 

 insect appears in the slender nails, which are placed a little way behind the tip of the 

 tarsal joint, instead of at the end. The species is dark brown, and closely pubescent 

 above, lead-colored and silky beneath, with the base and underside of the antennae, 

 coxae, lower surface of the head, sides of the breast, lateral margins and tip of the 

 venter, legs (excepting a dark stripe on the femora, the knees, and some clouds and 

 spots on the tibiae and tarsi), the outer edges of the pronotum, and surface of the 

 connexivum pale yellow or whitish. Just back of the head a narrow collar of orange- 

 yellow crosses the apex of the prothorax. The outer edge of the connexivum, and 

 also its transverse segmental sutures, are black, forming a strong relief upon the almost 

 orange-colored ground. A somewhat variable element appears in the pale fuscous 

 wing-covers, which, when pei'fectly fresh, exhibit about three whitish spots on the 



