1054 FAMILY XXXIX. — NOTONECTID^E. 



legs in great part dull yellow, in the darker forms tinged with fuscous. 

 Pronotum not quite twice as wide as long, its front portion and the vertex 

 of head finely, densely rugosely punctate. Scutellum at base slightly 

 wider than its length at middle. Length, 10 — 12 mm. 



Common throughout northern Indiana, less so in the south- 

 ern counties, June — November. Dunedin and Sarasota, Fla., 

 November — April ; recorded also from St. Augustine, Lake- 

 land and Lake City, that State. This is the most common, 

 most widely distributed and most variable in color of our back- 

 swimmers. Its known range covers lower Canada, the entire 

 United States and extends south through Mexico and Central 

 America to Chile. Six color varieties have been named, but 

 all merge into one another. In Indiana it occurs more often in 

 stagnant pools filled with decaying vegetation than in those 

 with clearer purer water. Uhler (1876, 339) says that about 

 Baltimore : ''It inhabits the foulest pools, and in the dirty slush 

 occasioned by the drainage of slaughter-houses and in the slimy 

 ponds attached to our brick-yards, it revels as if in full enjoy- 

 ment of the filth." The more robust form, shorter and less 

 dense pubescence, usually more distinct black markings and 

 wider basal interocular area distinguish undulata from variabilis. 



1193 (1351). Notonecta variabilis Fieber, 1851, 53. 



Oblong, subcuneiform. Color above usually a nearly uniform pale 

 straw yellow, the elytra more thickly clothed with longer paler pubes- 

 cence than in undulata; apical third of corium often with a vague oblique 

 fuscous bar; inner margin of clavus and disk of corium sometimes with 

 darker stripes; scutellum and membrane usually concolorous, sometimes 

 with their bases dusky; under surface in great part blackish, the pro- 

 stei*num, pleurae and connexivum paler; beak and legs dull yellow, the 

 tip of former and tarsal claws black. Pronotum twice as wide at base 

 as long at middle, its front portion less densely rugose than in undulata. 

 Length, 8 — 10 mm. 



Common in the streams of the northern third of Indiana, 

 July 18 — Oct. 21 ; not taken south of Marshall County. Ranges 

 from Quebec and New England west to Wisconsin and Ne- 

 braska and southwest to Florida and Kansas. The only Florida 

 record is indefinite and may have been based on an example 

 of undulata. This species is very close to undulata and Uhler 

 regarded it as only a small variety of that form. Bueno regards 

 it as distinct, and it is readily separable by the characters given 

 under undulata. It occurs more often in clear running streams 

 than in ponds, and is seldom if ever found in company with 

 undulata. 



