174 THE UNIVERSITY SCIENCE BULLETIN. 



A. Species over 6 mm. long — conchided. 



C. Head, including the large eyes, nearly as wide as the 

 pronotum in the male, a little narrower in the female. 

 Body robust; legs stout, interocular space not very nar- 

 row behind. Length, 7.5 to 9 mm. 



B. carinata Champ. 

 CC. Head, including the large, somewhat flattened eyes, dis- 

 tinctly narrower than the pronotum in both sexes; legs 

 rather slender, and, like the greater part of the body, 

 pale in color. Length, 6.5 mm. B. albida Champ. 



BB. Pronotum almost unimpressed^ though lateral carinte are well 

 marked in some males. Length, 6.7-8.1 mm. 



B. margaritacea Bueno. 

 AA. Species less than 6 mm. long. 



B. Eyes large and prominent; shape slender. 



B. 2ylutycnemis Fieb. 

 BB. Eyes large, but not prominent; shape more convex. 



B. elegaiis Fieb. 



The above table is adapted from Champion and from Bueno to sepa- 

 rate the species given in Van Duzee. Kirkaldy evidently did not recog- 

 nize either of Champion's species, for he says of B. albida Champ. 

 "Wahrscheinlich mit A. platycnemis identisch" and A. carinatus Champ, 

 he makes a synonym of his own B. antigone. The writer has been in- 

 terested in providing a- means of determining the bugs which he may 

 meet in his biological studies. He feels that such guides should have been 

 provided by those best acquainted with the groups, but where no keys 

 are available he has improvised them from the literature and such ma- 

 terial as has been authoritatively identified for him by such workers as 

 Bueno, Barber, Gibson, Parshley, etc. If the keys include synonyms and 

 false statements the reader is referred to Van Duzee's Catalogue and to 

 the descriptive literature. The writer wishes most heartily that there 

 were more papers dealing with the taxonomy of the aquatics, such as 

 those of Uhler, of Bueno, and of Barber. 



Bnenoa carinata Champion. 1901. 

 Biologia Centrali Americana, vol. 2, p. 372, 1901. 



"Elongate, robust, smooth, shining; head and pronotum sordid white, 

 the color of the latter modified by that of the mesonotum showing 

 through; the scutellum usually black in front and rufo-testaceous or 

 testaceous behind, sometimes entirely pale; the elytra sordid white, the 

 colour modified by that of the metanotum and the apex of the abdomen 

 showing through, these parts being usually black and the rest of the 

 upper surface rufo-testaceous or testaceous; the under surface, antennae, 

 and legs testaceous, the venter black, the terminal segment and some 

 spots on the connexivum excepted, the posterior femora beneath, and 

 sometimes the anterior and intermediate tibiae externally, each with a 

 dark streak down the middle. Head (with the large eyes) nearly as 

 wide as the pronotum in the male, a" little narrower in the female; 

 interocular space not quite twice as wide on the vertex as at the base, 

 considerably narrowed beneath, the vertex sulcate down the middle. 

 Pronotum about as long as the scutellum in the male, slightly shorter 



