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HUNGERFORD:. AQUATIC HEMIPTERA. 167 
KEY TO. GENUS NOTONECTA LINN. 
Rearranged from Bueno’s Notonecta of North America, 1905. 
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A. Small species, subrobust. 
B. Vertex* twice or less than twice the synthlipsis.+ 
C. Vertex 1% to 2 times the synthlipsis; width of pro- 
notum 1% times length; width of scutellum 1% times 
i the length; length of insect 9.4 mm. to 11 mm. 
3 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. WN. howardi. 
BB. Vertex more than twice the synthlipsis; vertex 2% times 
synthlipsis; width of pronotum 2 times its length; width 
of scutellum 1% times its length; length of insect 10 mm. 
to 13 mm. N. undulata. 
AA. Small, slender species. 
B. Vertex 3 times synthlipsis; width of pronotum 2 times its 
length; width of scutellum 114 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 1% times the 
length; length of insect 8 mm. to 8.8 mm. 
N. raleighi. 
CC. Vertex 6 to 8 times synthlipsis; width of pronotum 
144 times its length; width of scutellum 1% times its 
length; length of insect 10.7 mm to 12 mm. 
N. uhleri. 
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. 
: N. mexicana. 
CC. Vertex 3 times synthlipsis; width of pronotum 2 
times the length; width of scutellum 1% 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. 
+ Synthlipsis—distance between the eyes at base of the head, at the most constricted 
