I1EM1PTERA. 



lS 7 



Water-boatmen, they can leap into the air from the water and take 

 flight. 



There are three genera in North America. The greater number 

 of our common species belong to Notonecta. The following table of 

 the genera is from an unpublished work by Professor H. E. Sum- 

 mers : 



A. Apices of hemelytra entire ; the three pairs of legs similar in shape. Plea. 

 AA. Apices of hemelytra notched ; le^s dissimilar. 



B. Hemelytra much longer than abdomen; fourth segment of antennae 



longer than third. ANISOPS. 



BB. Hemelytra but little longer than abdomen; fourth segment of antennae 



shorter than third. NOTONECTA. 



Family XIII. — NepidA* 



( Water-scorpions.) 



The members of this family can be distinguished from other 

 aquatic Heteroptera by the presence of a long respiratory tube at 

 the end of the abdomen. This tube con- 

 sists of two long filaments, each with a 

 groove on its mesal side. By applying 

 these filaments together the grooves form 

 a tube, which conducts the air to two 

 spiracles situated at the caudal end of the 

 abdomen. By means of this apparatus 

 these insects are able to rest on the bot- 

 tom of a shallow pond, or among rubbish 

 or plants in water, and by projecting this 

 tube to the surface obtain what air they 

 need. 



With regard to the form of the body 

 two very different types exist in this fam- 

 ily. In one, represented by the genus 

 Ncpa, the body is a long-oval, flat and thin: 

 in the other, represented by the genus 

 R&natra, the body is almost linear and 

 cylindrical (Fig. 158). 



The Water-scorpions are carnivorous; and with them the first 

 pair of legs is fitted for seizing prey. In these legs the coxae 



—lianatra fusca. 



* Nepidae : Nepa, a scorpion. 



