246 MR. H.W. BATES ON BUTTERFLIKS FROM PANAMA. [June 23, 



the lower radial (or discoidal) is not visible across the wing — a cha- 

 racter which places it in the section Hymenitis. 



17. Ithomia (Cerattnia) leucania, n. sp. PL XXIX. fig. 2. 



$ . Fore wing above with the basal third orange-tawny ; costal 

 edge dusky at the base ; on the outer edge of the basal tawny part 

 there are two large subtriangular black spots, namely, one in the 

 middle of the cell, and one between the median nervure and its first 

 branch ; to these spots succeeds a short discoidal white cross belt, 

 separated into two elongate spots ; apical portion of the wing black, 

 crossed in the middle by a flexuous white belt, beginning on the 

 costal edge, and ending at a distance from the outer margin near the 

 middle ; besides which there is a submarginal row of seven large 

 white spots. Beneath, the same. 



Hind wing, above, orange-tawny, with a discoidal indented stripe 

 and the outer border (narrowly) black ; the border has a row of 

 white submarginal spots, which are partly indistinct. Beneath, the 

 same, except that the root of the wing has a yellow spot. Antennae 

 yellowish ; base black. Collar and wing-lappets orange-tawny. 

 Thorax marked with yellow. Expanse 2" 4'". 



This species might perhaps be more correctly treated as one of 

 the numerous local forms of Ithomia {Ceratinia) ninonia, in the 

 same way as /. panamensis is placed as a race of I. iphianassa ; but 

 the grouping of the different races of I. Jiinonia would lead to the 

 classing together of so many forms, graduating from the slight variety 

 to the well-segregated species, that the combined set would be almost 

 equivalent to a subgenus. I have described the way in which a great 

 part of Tropical America is peopled by these derived species and 

 semispecies in a former treatise (Linnean Trans, vol. xxiii. p. 524) ; 

 to the list there given the present new local form may be added. 

 The general practice of descriptive naturalists, especially ornitholo- 

 gists, is to treat every local form, however slight may be its distin^ 

 guishing characters from its nearest relatives, under a separate head, 

 in the same way as the more distinct species, leaving the impression 

 that all the successive forms numbered in order under a given genus 

 are neatly circumscribed species. This might be done to a certain 

 extent in the group of forms to which Ithomia ninonia belongs ; for 

 many of the local races, notwithstanding their close alliance to the 

 type, seem to be tolerably constant. But in one part, at least, of its 

 area the species presents so finely graduated a series of varieties that 

 the separation into these distinct local forms or assumed species is 

 impossible ; the whole must be considered as one variable form. If, 

 however, it be considered so, the facts of variation exhibited are such 

 as to compel us to infer that all the other more distinct local races, 

 allied to it, have been derived from the same stock ; for the varieties 

 show in some districts a tendency to segregation, in one of them 

 being more abundant than the others. Protean species, like I. ni, 

 nonia, are not uncommon in entomology ; and the close study of their 

 varieties with reference to their geographical positions throws great 

 light on the formation of races and species. Did none such exist. 



