234 



less perfect. In preparing the tables of food plants I have been 

 aided by communications from Messrs. Edwards, Saunders, Gundlach, 

 Riley and others, and especially by the extensive notes of Dr. A. W. 

 Chapman. Any well authenticated additions to this part of the 

 list would be very thankfully received. 

 Cambridge, January 15, 1875. 



Table foe the Determination of the Genera op North 

 American Butterflies; based upon the Structure and 

 Ornamentation of the Wings: 



1. Antennae widely separated at their base, the space between them more 

 than equalling half the vertical diameter of the eye ; the latter overhung 

 by a curving pencil of bristly hairs, originating at the outer base of the 

 antennae (Urbicolae.) 



1. Antennae approximate at their base, the space between them not equalling 



lialf the vertical diameter of the eye ; the latter without an overhang- 

 ing pencil of bristly hairs 2. 



2. Foretarsi of both males and females provided with a pair of claws like 



the other legs (Papilioiiides.) 



2. Foretarsi of males always, of females sometimes, with but a single median 



or with no apical claw 3< 



3. Antennae not closely approximate at their base, the space between them 



generally at least twice the width of the basal joint, the outer margin 

 of the latter infringing slightly on the eye ; fore legs perfect in the 

 female (Rurales) 63. 



3. Antennae closely approximate at their base, the space between them sel- 



dom surpassing the width of the basal joint ; the outer edge of the 

 latter never infringing on the margin of the eye ; forelegs of the fe- 

 male (as well as of male) atrophied (Njraphales) 4. 



4. Some of the nervures of the fore wings swollen at the base* ; cell of hind 



wings closed (Oreades) 5. 



4. None of the nervures of the fore wings swollen at the base*; or if swol- 



len, the cell of hind wings open 16. 



5. Middle tibiae profusely armed above with long and stout spines 14. 



5. Middle tibiae unarmed with spines on the upper surface, or with but slight 



short ones 6. 



6. Median nervure of fore wings greatly swollen at the base, halfway to 



its first divarication, the swelling not decreasing uniformly from the 

 base to the divarication 7. 



•Excepting two genera which may be diatinsciiished from the Oreades by the open cell of the 

 hind wings : Mestra, in which only the costul vein of the fore wing is swollen ; and Eunice, iu 

 which both costal and median veins arc about equally swolkui. 



