538 MR. H. W. BATES ON THE LEPIDOPTERA 



upper disco-cellular is very variable, there being a gradation from those species which stand 

 nearest to Cercdinia, which have an upper disco-cellular in both seses, to those approach- 

 ing Symenitis, in which this nervule disappears, the upper radial being then as a branch 

 of the subcostal (in the 2) or totally wanting (in the <?). 



2. Symenitis, part (Doubleday). 

 In this series of species the low^er radial and upper disco-cellular exist in the <S , 

 although the lower radial is more or less aborted, whilst in the ? the upper radial becomes 

 joined as a branch to the subcostal, its corresponding (the upper) disco-cellular being 

 wanting. The lower radial is removed nearer the costa, terminating at the apex of the 

 wing, the median branches being rather widely spread. 



3. Symenitis. 



The hind-wing low^er disco-cellular, in the extreme forms of the group, anastomoses 

 immediately with the subcostal in both sexes ; consequently both middle and upper disco- 

 cellulars are entirely absent, the low^er and upper radials being as branch and sub-branch 

 of the subcostal. The median branches are very widely spread, and the wing-cell is 

 thrown close to the fore margin of the wing. In the less extreme species, both disco- 

 cellulars exist in the c7 ; but they are very short, and the lower radial is always placed 

 nearer the subcostal than in group 2. 



The explanation of this diversity in the system of neuration of the hind wing in the 

 genus Ithomia seems to be this : — The species exhibit from one end of the scale to the 

 other the gradual determination of the nervures towards the costa. In Na/peogenes, in 

 Ceratinia, in Mechanitis, and still further in Sais, we have seen the radials brought 

 within the domain of the median nervure ; in SJiomia they show the opposite tendency, 

 namely, to connect themselves with the subcostal system of nervures — a tendency which 

 progresses through our sections 1 (^Ithomia proper) and 2, and culminates in Symenitis. 

 Symenitis, therefore, exhibits the extreme development of a plan of wing-neuration totally 

 unlike anything existing in the rest of the section Rhopalocera. 



In this direction it may be said to display the type of the beautiful order Lepidoptera 



■ in its greatest perfection. It is a curious fact that none of the delicate species comprised 



in the subgenus Symenitis are found in the Amazon plains : they seem to be confined to 



the more elevated valleys of the Andes, in Peru and New Granada, and to the higher 



tropical latitudes of Mexico and S. E. Brazil*. 



* The following described species of Ithomia belong to the Hymenitis section : — 



1. I. diaphana, Drury, ii. pi. 7. — Jamaica, St. Domingo. 



2. I. esula, Hewits. Exot. Butt. Ithomia, fig. 83. — New Granada. 



.3. I. Theudelinda, Hewits. Exot. Butt. Ithomia, fig. 146. — New Granada. 



4. I. DuilUa, Hewits. Trans. Ent. Soc. n. s. vol. ii. pi. 23. fig. 3. — New Granada. 



.5. I. Aitdromica, Hewits. Exot. Butt. Ithomia, fig. 38. — Venezuela. 



6. /. Eruca, Hewits. Exot. Butt. Ithomia, fig. 81. — Brazil, 30° S. lat. 



7. /. Moryane, Hiibner, Zutriige, figs. 869, 870. — Mexico. 



8. I. Dercetis, Doubled. & Hewits. Gen. Diurn. Lep. pi. 18. fig. 6. — Venezuela. 



9. I. Nero, Hewits. Exot. Butt. Ithomia, fig. 37.— Mexico. 

 10. I. Oto, Hewits. Exot. Butt. Ithomia, fig. 39. — Guatemala. 



