H. Onslow 223 



Var. nigntsfKintdta. 



(»StM» I*lrtt4» IX. No. 2i).) All tho \\'\i\^ Jirr firirly M|MH-kl«M| with 

 black, which fjivt*8 tht' iiimn't a H<M»(y a|)|M>aniii<'(', timt. «'xt<inls «iv«t tht* 

 oraiigi^ fiiMciii, It is siiid that this variation is n<»t inherited, and 

 Mr IWritt has UtU\ uw that he t*ail«'(i to hrrcH a ^rratcr prrcrnta^r of 

 ajK-ximcns from uiffntsiHtrsttUi ? x niifvosparitaUt J than ho \v;ls ahl*- 

 to obUiiii fn»ni wiM larvao colloctoti in the siuno n('i^'hlMMirli<M.<l. 

 Mr li^iynor has also had a vory similar cxjx'rirnc*'. I (»ncr oht,;iin«Mi a 

 sin^lo s|)«»oinion of inffntspdrsata J^ from larvae cojlrctcd in Kent, whif^h 

 was painni to a nither<iark female from the s;ime Im^ality : out of 12 off- 

 spring only one % showed a very faint trace of melanic sut!*u.sion. 



Var. iochalca. 



(See Plate IX. No. ()().) 'Phis variety hears a certain relati(»nship 

 to the prectnling one and to vwlacea. in that they all have a melanir 

 suffusion which extends over the surface of the wing. Th<' ditV«'renc«* 

 in apfH»ar.ince is however most striking, as may he seen by reference to 

 Plat4» IX. In iochdlca the wings are suffused with a pecidiar metallic 

 hue duo to the addition of black pigment to the scales of the y«'llow 

 variety of kicticolor (i.e. chrysostrota), which caus(»s a desaturation of 

 the yellow colour. In nigrospavsaUt on the other hand, the suffusion 

 is more intense and often has a mottled appearance, especially when 

 observed through a lens. It is true that the specimen illustrated 

 (No. 29) has a white and not a yellow ground. Nevertheless, when 

 nigrosparsata is combined with lutea, the difference is if anything more 

 striking. 



(h) Distribution of black pigment in sufficsed viwieties. 



A yellow insect showing this suffusion was bred too late to be included 

 in the plate. A seiwrate illustration, however (see Plate X), shows the 

 difference between the dejx)sition of the melanic pigment in the yellow 

 variety of nigrosjxirsaki, and in a specimen (^f iochalca as they appear 

 under the micro.scope. The j>ortion of the f(n*c wing of the nigrusjxtmatif 

 illustrated is much closer to the costa than that of the iochalca, and 

 consequently the scales are smaller and narrower. A comparison of the 

 two figures shows that the scales of iochalca (see Plate X, Fig. I) are 

 a uniform buff, the black pigment being rather more abundant near the 

 base of the scales than at the tip. For this reason th<' pigmentation is 

 somewhat obscured, bec«'iuse the darkest portion is always covered by the 

 pale overlapping jxjints of the scales in the row preceding it. The wing 



