Sept., 1905.] Bueno : Notonecta of North America. 149 



for separating them. I have used this method in the diagnostic tables 

 following, being of the opinion that in general, proportional measure- 

 ments of the hardened chitinous skeleton will be found to be constants 

 in the majority of insects, and being more permanent than other 

 characters, give an at all times reliable standard for the separation of 

 species. This theory has not had the test of extended practical ex- 

 perience, except in this group, where hundreds of measurements have 

 born out its efficiency. 



Analytical Tables. 



Family NOTONECTID/E. 



Rostrum 3- to 4-jointed, first pair of legs inserted on the posterior margin of the 

 pronotum, scutellum large. 



Key to the Subfamilies. 

 Hind tibiae and tarsi ciliated, abdomen keeled, hairy, eyes very large, conspicuous. 



Notonectince . 



Hind tibia; and tarsi apparently not ciliated, abdomen neither keeled nor hairy, 



rostrum 3 -jointed, eyes small Pleince. 



Subfamily NotoNECTIN.f;. 



Key to the Genera. 



Eyes not contiguous at base, posterior femora not reaching the apex of the hemelytra. 



Pronotum not very transverse, wings present, hemelytral area distinct. 



1 (2) Last segment of the antennae much shorter than penultimate, hind tarsi 



without claws Notonecta. 



2(1) Last segment of the antennae much longer than the penultimate, hind 

 tarsi with cla ws Buenoa. 



Genus NOTONECTA Linne. 



Synopsis of Species. 

 1(7 and 10) Small species, subrobust. 



2 (5) Vertex twice or less than twice the synthlipsis. 



3 (4) Vertex l 1 /^ to two times the synthlipsis ; width of pronotum one and 



three quarters times the length ; width of scutellum one and one 

 half times the length ; length of insect 9.4 mm. to 11 mm. indica. 



4 (3) Vertex twice the synthlipsis ; width of pronotum one and four fifths 



times its length ; width of scutellum one and one fifths times its 



length; length of insect 10.2 mm howardii. 



5 (2) Vertex more than twice the synthlipsis. 



6 Vertex two and one half times the synthlipsis ; width of pronotum twice 

 its length ; width of scutellum one and one fifth times its length ; 



length of insect 10 to 13 mm undulata. 



7 (I and 10) Small slender species. 



8 (9) Vertex three times the synthlipsis; width of pronotum twice its length ; 



