10 INTKODrCTlOX. 



costu or vein 1 iiiul inner ni;irj;in may he present. The present 

 form ot' neuration arose IVoni a sy>tem of siinple loii;^itii(linal veins, 

 which by the union of their hasal portions fornu-d the present 

 hranchiiii; system ; tlais the diseocflhilars which ch)se the cell tif 

 each win^ wore formed by the junetion of the htisal portioiiH of the 

 three radial veins, tlie l»a.sal stem l)ein^' then aborted. lea\-inp only 

 an oiitwardly-directe<l tritid fork of whi.h the radials are tlie 

 extremities. The whoh* process in itn various sta;,'es may !)e clearly 

 seen in such ^generalized forms as tlie f'nsgi'/r, Psifchulit , and 

 Zijinrnhlf ; and the neuration of thr extinct ancestor of the L>pi'lo- 

 ptern must have consisted of at lea>t tifleen simple lonj^itudinal 

 veins in each winp, and probably more, as in several groups vein 1 h 

 of the hind wini: is lorked at ba.se. Vein I, the lowest radial, ban 

 become ix'rmanently con!iect<'d with tiie t wo-branclied median 

 nervure *, and vein <5, almost without exception, with the fivt»- 

 branched subcostal nervure : but the position of vein .') differs much 

 in the several ^rouj»s of families, according' to whether it retains its 

 orij^inal medial position or is attracted towards the median or 

 subcostal systems. 



The fore and hind wing.^ in th<' majority <d familie.s <»f Moths 

 are connected by the " frenulum '* di'veloped from hairs arisinj; from 

 the base of the costa of hind win,:: and fitting into the " retinaculum " 



^' ,^' * n 



■V. , 



. t\ 

 f J c n 



A 1\ 



4 



in 

 1 2 



Fig. (l. -1. (^. L*. 9- (From M<»thj» of India, vol. i.) 

 .\. Fore winp. D. Hind wing, 



/. Fn'nulum. •■«.». J^ubo«iHinl ncmiro. 



r. Ri'tiuaruluni. m.ti. .Median ncTTuro. 



(•.//. Cosud niTTurc. i n. Internal nervure. 



on the fore win*;, which consists of a fold from the underside of the 

 costa, a mcm]•ranou^ hook, or tuft of hair arisini: from the costal 

 nervure, or a tuft of hair arising from the median nervure or rarely 

 from the wing-membrane below it. The form of the frenulum is 

 of great use in determiidng sex, as in the males of all the forms 

 that possess it, it consists of hairs firmly soldered together so as to 

 form a single l^ristle, articulating with the retinaculum arising from 

 the costal nervure, whilst in the female it consists of three or more 

 bristles (in a Cossid I have found as many as nine) articulating 

 with the retinaculum arising from the median nervure. In the 



* A. Spuler, ' Zur Phylogenie und Ontogenie des Fliigelgeiiders der Schmet- 

 terlinge.' 



