46 



The scales are of two kinds — a long and narrow, and a broader 

 and short kind placed alternately. In large numbers of transparent 

 species the long narrow scales have become hairs standing up away 

 from the membrane, and the broader scales which are shaped like a 

 fan, become greatly reduced in size, so that they have the appearance 

 of the letter Y. 



The situations where one finds Ithomiids is very varying, as might 

 be surmised from the very difi'erent elevation. Bates found in the 

 Amazon region that they were always present in the darker, denser 

 portions of the forest, especially in the humid ai-eas. He says, also, "I 

 found the numberof species to increaseintravellingfroniEastto West, 

 from the Lower Amazon to the eastern slopes of the Andes. They 

 were rare in the somewhat drier country which borders the Lower 

 Amazon about the middle course." This account is doubtless true 

 of the Amazon, and probably all low lying similar regions, as 1 can 

 testify myself from experience in British Guiana, but it is now 

 known that with difi'erent altitudes different conditions prevail with 

 those species that inhabit them, but a moist atmosphere seems to 

 be a necessity for their existence. In 1862 there were only 2B3 

 species known, and they were very largely lowland species ; but now 

 there are 950 known forms, from every elevation up to 10,000 feet 

 at least. 



I have left it till now to speak of the remarkable neurational 

 structure of Ithomiine imagines. All the species of the sub-family 

 are structurally diti'erent sexually in the hindwing, while the fore- 

 wing remains the same. In some genera such as in Ceratinia there 

 are species that resemble species of Xapeoj/ejies, where the males can 

 with certainty be differentiated by the neuration if not by colour or 

 pattern, but the females are in some cases hardly distinguishable at 

 all. A good example is to be found with Ceratinia antea and 

 Xapeoi/enes (/li/cera, both from Ecuador. The genera to which these 

 belong are genetically very close, but where strong resemblance 

 is found between species of less closely related genera they can 

 always be separated in both sexes by the structure. In all the 

 larger forms belonging to the most generalized types, such as are to 

 be found in the genera Olyras, Athesis, Entresis, Mdiiuca and 

 Mechanitis, as well as in Dircenna, Ceratinia, and Napeogenes, the 

 great characteristic is that the cell of the hindwing of the male is 

 longer than in the female. The upper discocellular in the male is 

 produced towards the costal margin, forming as it were an extra 

 angular piece to the cell. In Ohjras and Melinaa the difference is 

 small, in Athedsi and Mechanitis it is more marked, but in [>ircenna, 

 Ceratinia and Xapeoj/eiies it is very great. In Ceratinia and 

 Napeogenes the cell of the male is almost extended out to the apex 

 of the wing, so that vein 7 becomes almost non-existent, but 

 Ceratinia differs from Napeogenes in having a veinlet in the cell 

 which is absent in Napeogenes. In the female of Olgras, veins 6 and 

 7 are either united, or very close at their origin, while the male 



