Siphunculata and Hemiptera 277 



g. Ocelli present; beak four-segmented. Ochterid^ and 



Nerthrid^. 



gg. Ocelli wanting; antennae more or less hidden in a groove. 



h. Anterior coxa inserted at or near anterior margin of the 



presternum; front legs raptorial; beak three-segmented. 



BELOSTOMlD.aE (with swimming legs),NEPiD/E, Naucorid^. 



i. Metastemum without a median longitudinal keel; antennse 



always four -segmented. 



j. Beak short, robust, conical; the hairy fleck on the corium 



elongate, large, lying in the middle between the inner 



angle of the membrane and the outer vein parallel to 



the membrane margin; membrane margin S-shaped. 



k. The thick fore femur with a relatively deep longitudinal 



furrow to receive the tibia. Several American 



species (fig. igf.) . . .Belostoma ( = Lethocerus Mayer) 



kk. The less thickened fore femur without such a furrow 



B. griseus. Benacus Stal. 



jj. Beak slender, cylindrical; the hairy spot on the corium 



rounded lying next to the inner angle of the membrane. 



k. Membrane large, furrow of the embolium broadened. 



Z. aurantiacum, fluminea, etc Zaitha 



kk. Membrane very short; furrow of emboUum not 



broadened. Western genus. . . ; Pedinocoris 



ii. Metasternum with a long median longitudinal keel. South- 

 western forms Abedus ovatus and Deniostoma dilatato 



hh. Anterior coxae inserted at the posterior margin of the 

 presternum; legs natatorial. Back swimmers (fig. 19 b.) 



■ NOTONECTID^ 



i. Apices of the hemelytra entire; the three pairs of legs 

 similar in shape; beak three-segmented; abdomen not 



keeled or hairy Plea Leach 



ii. Apices of hemelytra notched; legs dissimilar; beak four- 

 segmented; abdomen keeled and hairy, 

 j. Hemelytra usually much longer than the abdomen; 

 fourth segment of the antenna longer than the third 



segment; hind tarsi with claws Bueno Kirk. 



jj. Hemelytra but little longer than the abdomen; fourth 

 segment of the antenna shorter than the third seg- 

 ment; hind tarsi without claws (fig. 19b) . .Notonecta L. 

 ff. Antennae longer than the head; or if shorter, then the eyes and 

 ocelli absent, 

 g. Eyes, ocelli, and scutellum wanting; beak three-segmented; 

 head short; hemelytra always short; membrane wanting. 



Insects parasitic on bats Polyctenid^ 



gg. Eyes present. 



h. First two antennal segments very short, last two long, pilose, 

 third thickened at the base; ocelli present, veins of the 

 hemelytra forming cells. Dipsocorid^e ( = Ceratocombi- 

 D^) including Schizopterid.e. 



