HEMIPTERA 97 



FF. Beak four-jointed. 



G. Front legs fitted for grasping prey, the tibiae being armed with 

 spines and capable of being closed tightly upon the femora, which 

 are stout. In the forms with long wings the membrane is usually 

 furnished with four long veins, bounding three discal cells which are 

 often open. From these cells diverge veins which form several 



marginal cells (Fig. 165). p. 103 Nabid^e 



GG. Front legs fitted for walking. 



H. Hemelytra with cuneus; membrane with one or two closed cells 



at its base; tarsi furnished with an arolium. p. 101 . . . . Mirid^e 



HH. Hemelytra without cuneus. Membrane with four or five simple 



or anastomosing veins arising from the base; or with a large 



number of veins arising from a cross-vein at the base. 



I. Ocelli wanting. 



J. Exceedingly flat bugs. p. 108 Aradid^e 



JJ. Rather stout and heavily formed bugs. p. 104 



PYRRHOCORID/E 



II. Ocelli usually present. 



J. Head with a transverse incision in front of the ocelli, which 



are always present, p. 107 Neidid.e 



JJ. Head without transverse incision. 



K. Membrane with four or five simple veins arising from 

 the base of the membrane, the two inner ones sometimes 



joined to a cell near the base (Fig. 173). p. 105 



LyCEIDjE 



KK. Membrane with many, usually forked veins, springing 

 from a transverse basal vein (Fig. 175). p. 106 



COREID/E 



DD. Antennae five-jointed.* 



E. Tibiae armed with strong spines; hemelytra with the clavus markedly 



thicker than the membrane, p. 108 Cydnid^e 



EE. Tibiae smooth or with small spines. 



F. Scutellum narrowed behind, only rarely almost covering the abdomen. 



p. 106 Pentatomid;e 



FF. Scutellum not narrowed as in the Pentatomidae, very convex, nearly 

 or quite covering the abdomen, p. 108 Scutellerid^e 



* In some cases there are minute intermediate joints between the principal joints 

 of the antennae; for the purposes of this table these intermediate joints are not 

 counted. 



Family Corixid^e 



The Water-boatmen 



The family Corixidae includes oval, gray-and-black mottled bugs, 

 usually less than half an inch in length, which live in lakes, ponds, and 

 streams, in both stagnant and running water. The 

 characteristic form and markings of these insects are 

 shown in Figure 151. 



The beak is very short, the middle legs are very 

 long and slender, and end in two claws, while the hind 

 legs are long, flattened and fringed for swimming. The 

 water-boatmen have the body flattened on the dorsal 

 side and they swim on the ventral side in normal posi- 

 tion. 



The body of these insects, as they swim through 

 the water, is almost completely enveloped in air, which 

 glitters like a silver armor. This air is purified by contact with the fine 

 particles of air scattered through the water; so that the insects can breathe 



