538 MR. II. W. BATES ON THE LEPIDOPTERA 



upper disco-ocllular is very vai'ia1)lc, there being a gradatiou from those species which stand 

 nearest to Cevatluia, which have an upper disco-cellular in both sexes, to those approach- 

 ing Htjwcmt'is, in which this nervule disappears, the upper radial Ijeing then as a branch 

 of the subcostal (in the $) or totally wanting (in the <S). 



2. Ilymenltls, part (Doubleday). 

 In this series of species the lower radial and upper disco-cellular exist in the c?, 

 although the lower radial is more or less aborted, whilst in the 2 the ujjper radial becomes 

 joined as a branch to tlie 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 l)ranc]ies being rather widely spread. 



3. Ilymeiiitis. 



The hiiul-wing lower disco-cellular, in the extreme forms of the group, anastomoses 

 immediately with the su1)Costal in lioth sexes; consequently both middle and upper disco- 

 cellulars are entirely absent, the lower and upper radials being as branch and sub-branch 

 of the sul)costal. The median 1)rauehes 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 cr ; luit they are very short, and the lower radial is always placed 

 nearer ihe subcostal tlian in group 2. 



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

 genus TfhoDiia seems to be this : — The species exhiliit from one end of the scale to the 

 other the gradual determination of the nervuivs towards the costa. In Napeogenes, in 

 Crratiutd, in ]fL'cJ/(u/i//s, and still further in Sa/s, we have seen the radials brought 

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

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

 progresses tlirough our sections 1 {Ithoniia proper) and 2, and culminat(>s in llijiiioiitls. 

 IIi/iiH'i/i//s, therefore, exhil)i<s the extreme develo[)m(Mit of a plan of wing-neiu'ation totally 

 unlike anything existing in the rest of the section l{ho})alocera. 



In this direction it may l)e said to display the type of the beaiitiful oi'der Lepidoptera 

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

 in the suljgeuus IL/mpDiUs arc^ found in the Amazon plains : they seem to ha confined to 

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

 tro])ieal latitudes of Mexico and S. ]■]. lirazil*. 



* The fnlliiuin:;- ilrsnibcd s[)i'ci(S of Ilhomiii bclmig to tlic Ilympnitis section : — 



1. I. <n(ip}i(iiiii, Dniry, ii. ]il. 7. — Janmicn, St. Domingo. 



■_'. /. esiihi, llrwits. Kxot. Butt. Uhomiit, tig. S.S. — New Granmla. 



Ii. /. Thrii,/rli,i,la, Ilewits. Exot. Butt. Ulwrnin, fig. N().-^Ne\v Granada. 



■I. /. Dinlliii, Ilewits. Trans. Enl. Sue. n. s. vol. ii. pi. ■_';;. fig. .'i. — \c\v (Jranada. 



U. I. .tiiilrnniirn, Ilewits. Exot. Butt. Ithomia, fig. .'{S. — Veneznela. 



6. /. EniPd, Ilewits. Exot. Butt. Ithomia, fig. 81.— Brazil, 'M)° S. lat. 



'. I. A/on/a)ir, liiilnier, Zntriige, figs. 8fi!), 870. — Mexico. 



8. /. l)rn;-ti.s, Donliled. & Ilewits. Gen. Dinrn. Lep. ])1. 18. fig. fi.— Venezuela. 



9. 7. Nero, Ilewits. Exot. Butt. Ithomia, fig. ,'?7.— Mexico. 

 K). /. Oto, Ilewits. Exot. Butt. Ithomia, fig. M!).— Guatemala. 



