hungerford: aquatic hemiptera. 167 



KEY TO GENUS NOTONECTA LINN. 



Rearranged from Bueno's Notonecta of North America, 1905. 



A. Small species, subrobust. 



B. Vertex* twice or less than twice the synthlipsis.f 



C. Vertex 1^^ to 2 times the synthlipsis; width of pro- 

 notum 1% times length; width of scutellum 1% times 

 the length; length of insect 9.4 mm. to 11 mm. 



N. indica. 



CC. Vertex 2 times synthlipsis; width of pronotum 1% 

 times its length; width of scutellum IVs times its 

 length ; length of insect 10.2 mm. N. howardii. 

 BB. Vertex more than twice the synthlipsis; vertex 2^/2 times 



synthlipsis; width of pronotum 2 times its length; width 



of scutellum IVs times its length; length of insect 10 mm. 



to 13 mm. N. undiilata. 



AA. Small, slender species. 



B. Vertex 3 times synthlipsis; width of pronotum 2 times its 

 length; width of scutellum IVs times its length; length of 

 insect 8.2 mm. to 10.2 mm. N. variabilis. 



BB. Vertex more than 3 times synthlipsis. 



C. Vertex 6 times synthlipsis; width of pronotum 1% 

 times the length; width of scutellum IVi times the 

 length ; length of insect 8 mm. to 8.8 mm. 



TV. raleighi. 



CC. Vertex 6 to 8 times synthlipsis; width of pronotum 

 1 % times its length ; width of scutellum 1 Va times its 

 length; length of insect 10.7 mm to 12 mm. 



N. iihlef-i. 



AAA. Medium sized, robust species. 



B. Vertex at least 3 times synthlipsis. 



C. Vertex 3 to 41/2 times synthlipsis; width of pronotum 

 21/^ times its length; width of scutellum 1^/2 times its 

 length; length of insect 11 mm. to 14 mm. 



N. mexicana. 



CC. Vertex 3 times synthlipsis; width of pronotum 2 

 times the length; width of scutellum IVt times its 

 length; length of insect 12.1 mm. to 14.4 mm. 



N. irrorata. 

 BB. Vertex less than 3 times the synthlipsis. 



C. Vertex 2 to 2^^ times the synthlipsis; width of pro- 

 notum 2 times its length; width of scutellum IVs 

 times its length; length of insect 12.1 mm. to 17 mm. 



N. lutea. 



* Vertex — distance between the eves at the front. 



t Synthlipsis — distance between the eyes at base of the head, at the most constricted 

 part. 



