282 
14 
15 
DRAGONFLIES OF NORTH AMERICA 
Last abdominal segment of male with no bifid process.......... 
oes BSA LSR ae OS he Rane rans so an eon nat Ee Enallagma, p. 311 
Last abdominal segment of male with a bifid dorsal process. .... 
SS CRESS RNS CIEE AOR ONS Oe Sr Zoniagrion, p. 342 
Fore wing stigma of male bordered by the costa; hind tibia of 
female with external black stripe............ Ischnura, p. 342 
Fore wing stigma of male removed from costal margin; hind tibiae 
of femaie wholly pale) so. v.20 pal, oh eee Anomalagrion, p. 357 
Nymphs* 
Gills half as broad as long: no mental setae................. 2. 
Gills not more than one third as broad as long: mental setae 
presente) aid ett we inal va~ eq: ona hha tee) eee 3. 
hateral setae tad hour. lapiccateoeat laa) eee pel aa Argia, p. 286 
Lateral setae 0 (occasionally 1)............. Hyponeura, p. 284 
Hindangles of head angulate’. ji.) (.. a: 4d 52 tae eects eee 4, 
Hind} anglevof ead rounded .).'....... 0. oo oc ee eee 5. 

Fic. 45. The nymph of Amphiagrion. 
Gills widest in middle, one third as broad as long.............. 
dose GIL Bird UO ARR is Oe cca in Amphiagrion, p. 304 
Gills widest toward the distal end, one sixth as broad as long... 
Pa AOE AR TUNG SC a RUT avM aero me NU me Chromagrion, p. 309 
Mental setae T or 22.3 7 ei ee ee ae ce ee 6. 
Mental setae 3 or more! 20 0 8 2 Oe a eee as 
Mental setae ta. 0, icles ars cate hee) eee oer N ehalennia, p. 306 
Mental setae 2. i) OL, i) A Se ees 8. 
* From Guide to the Study of Fresh-water Biology, by James G. Needham 
and Paul R. Needham. 
