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 1% times its 

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

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

 synthlipsis; width of pronotum 2 times its length; width 

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

 to 13 mm. N. iindulata. 



AA. Small, slender species. 



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

 length; width of scutellum 1% 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 IV^ times the 

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



N. raleighi. 

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

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

 length; length of insect 10.7 mm to 12 mm. 



N. xihleH. 

 AAA. Medium sized, robust species. 



B. Vertex at least 3 times synthlipsis. 



C. Vertex 3 to 4^/^ times synthlipsis; width of pronotum 

 2% times its length; width of scutellum 1% times its 

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



TV. mexicana. 

 CC. Vertex 3 times synthlipsis; width of pronotum 2 

 times the length; width of scutellum IVi, 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 1% 

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



N. lutea. 



* Vertex — distance between the eyes at the front. 



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

 part. 



