A GUIDE TO THE STUDY OF BRITISH WATERBUGS. 297 



— Less robust; narrower across inter mediate coxav, 



abdomen not depressed on each side of central 



keel 6. thoracicus, Scbumm. 



4. $ . Sixth abdominal segment armed beneath 



with two strong teeth ; 2 seventh abdominal 

 segment (first " genital ") transverse, im- 

 pressed beneath at base . . 10. odontoga'ster, Zett. 



— $ witbout the teeth ; $ seventh abdominal 



segment not transverse .... 5 



5. First segment of posterior tarsi more than twice 



as long as second ; base o{ pronotum more 

 angular, posterior lobe strongly keeled ; species 

 8-13 mm. long ...... 6 



— First segment less than twice as long as the 



second ; base of pronotum less angular, pos- 

 terior lobe more feebly keeled ; species 6^- 

 1\ mm. long. .... 9. argentatus, Schumm. 



6. Large species, 12-13 mm. long. Large yellow 



tubercle on metasternum ; anterior femora 

 black above ; mesopleura very wide ; sub- 

 marginal flavescent line on pronotum not con- 

 tinued on to anterior lobe ... 7. gibbifer, Schumm. 



— Smaller, 8-10 mm. ; no metasternal tubercle 



(or, if present, small and black) ; anterior 

 femora pale, with two black lines ; mesopleura 

 narrower ; submarginal line continued on to 

 anterior lobe . . . . . .8. lacustris (Linn.) 



4. G. asper (Fieb.) ?. 



= G. thoracicus, Flor (nee Schumm.) ?. 



= G. lateralis, Schumm ?. 



I have not been able, up to the present, to settle the synonymy 

 of this species. G. asper (Fieb.) and G. lateralis, Schumm., 

 whether synonymous themselves or not, are readily separable 

 from G. thoracicus and G. costce by the fact that in the first two 

 the venter is channelled {canaliculate), in the last two keeled 

 (carinate). Of the European species with carinate venter, I seem 

 to have two in my collection. 



No. 1 represented by a single male from Pitlochry. To this 

 species are referable three apterous females from Mr. Saunders's 

 collection (one now in mine!). I have not seen specimens from 

 any other country than Scotland, the records being from Pit- 

 lochry, Loch Galby, and Forres.* 



No. 2 represented by a winged female from Hungary, given me 

 by Dr. Horvath. I have seen specimens of this from Gibraltar. 



:;: I know the country around Forres fairly well, and I much doubt that 

 this species was really taken there. I expect Norman included in the term 

 "Forres" individuals taken as far afield as Granttown and other likelier 

 places. 



