THE CANADIAN ENTOMOLOGIST. 71 



(Linn.) My genus Hydrometra is easily distinguishable 



from Gerris in the following characters : Head drawn out into a long, 

 cylindrical snout, recurvant and in a longitudinal groove the beak. 

 These insects have the body very narrow, slender and linear, the head 

 very long and slender, carrying at the extremity of the elongate snout 

 two setaceous four jointed antennae. The eyes are large and globular 

 and are situated near the middle of the snout; Linnaeus mistook them for 

 tubercules. The thorax is long and cylindrical, the tegmina are very 

 short and narrow and lie on the back, not occupying more than the 

 interval between the second and third pairs of legs. The abdomen is very 

 long and slightly larger than the anterior portion of the body ; it is 

 cylindrical and has two longitudinal keels, one on each side of the 

 border. The legs are very thin and long, the middle pair being nearer 

 the anterior pair than to the posterior. Hydrometra loves aijuatic 

 places, and runs with some agility on the surface of the water, but not 

 very rapidly. It is this habit that gives them their name Hydrometra 

 (water measurer).' When Latreille first established this genus it con- 

 tained but two species, one from Europe, H. stagnorum, and another 

 from the West Indies, the first serving as the type. 



Cimex stagnorum (Linn.), Latreille's type, was placed by Linnaeus, 

 who described it, in his heterogeneous genus Cimex, which included 

 many widely different Hemiptera. Later naturalists in dividing up this 

 genus placed H. stagnorum in various genera, such as Gerris and Emesa, 

 until it was rescued by Latreille and placed in a genus by itself, which its 

 unique characters well merited. Later, Burmeister,* setting aside 

 Latreille's work, proposed the generic name Limnobates for this insect, 

 and this name is frequently to be met with in comparatively recent books. 



The United States, like Europe, has up to the present but a single 

 species, and this ( H. lineata) was first described by Thomas Say.f I 

 quote the following : " H. lineata. Fuscous ; hemelytra dull whitish 

 with black nervures. Inhabits United States. Body fuscous or brown, 

 more or less deep ; hemelytra dull whitish or dusky, with black nervures ; 

 tergum pale, quadrilineate with black ; two of the lines on the edge and 

 the interval between the two inner lines, dull whitish or bright yellow > 

 the incisures of the segments more or less black ; beneath and feet obscure 



* " Handbuch der Entomologie" (1839), Vol. II., No. 1, p. 210. 

 t The complete writings of Thomas Say on the Entomology of North America. 

 (Leconte's Edition J, \'ol. 1., p. 361. 



