236 RHOPALOCERA MALAYANA. 



spots on the under surface of the wings, and wliich in the figure here given appear 

 greenish.* 



Genus DRUPADIA. 



Drujmdia, Moore, MS. 



This genus is allied to Cataparihna iu having only three subcostal nervules to the anterior wings and 

 in possessing three tail-like appendages to the posterior wings. The differential points exist most strongly 

 in the posterior wings, which are convex at base and then strongly oblique to apex, which is subacute ; the 

 posterior margin is oblique to apex of middle median nervule, when it is more produced and contains a 

 tail-like appendage at the apices of the second and third median nervules and of the submedian nervure ; 

 the abdominal margin is very strongly cleft near anal angle ; the costal nervure does not extend to about 

 apex as in Catapmcilma, but terminates on costal margin at about two-thirds of its length ; the subcostal 

 nervules bifurcate a little beyond middle of cell, and the first and second median nervules have an 

 apparently common origin a little before end of cell ; the internal nervure is straight and terminates just 

 above the excavation of the abdominal margin. The palpi are robust and porrect, the second joint clothed 

 with coarse adpressed hairs projecting fully two-thirds of its length beyond the eyes ; the third joint is 

 slender compared with the second joint, but robust compared with the corresponding joint of many other 

 somewhat allied genera. Legs moderately robust. 



Drupadia superficially reseml)les the following genus {Bidiiaiuhi), and as arranged by 

 Mr. Moore it included the species which here stands as the type of Biduaiula. The 

 resemblance, however, is only superficial, as one genus possesses three subcostal nervules to 

 the anterior wings, and the other genus is provided with four. 



The extent of its geographical distribution cannot at present be estimated till the 

 whole of the LijcwiudLC are properly monographed, t 



1. Drupadia moorei.; (Tab. XX., fig. 21 <? , 20 and 30§ $ .) 



Sitlion Moorei, Distant, Ann. & Mag. Nat. Hist. ser. 5, vol. x. p. '24G (1882). 



Male. Anterior wings above very dark and glossy fuliginous-brown, with an irregular reddish spot 

 or suH'usion situate at end of cell and bases of the median nervules : posterior wings bright and somewhat 



* The stnicturc iind nature uf these silvery spots have lately been investigated by Mr. Geo. Dimmock (' Psyche,' vol. iv. 

 pp. 64 and t)6), and he has not only shown that " Leydij,' was the tirst, in 1855, to call attention to the presence of air between 

 or beneath tlieir cliitin layers as a cause for certain silvery spots and scales on insects," but has treated the question more 

 exhaustively, and has argued (taking the silvery spots of Argynnis idalia as an example) that these spots not only contain air, 

 but are " simply milk-white by transmitted light." " The difference is that there must be in the silvery scales a polished surface 

 towards tlie observer. Ground glass does not appear silvery, but what is the surface of the smoothest polished plate of glass but 

 finely gi-ound glass ? Ground glass diflers from polished glass only in degree ; in ground glass the scratches are so coarse and 

 so abuudaut as to turn most of the hght-waves into the glass again! where they are lost. In polished glass the scratches are still 

 present, but have become so small that even the waves of liglit are large in proportion to them, and so the light-waves reflect 

 as if from a theoretically flat surface. But something more than a polished glass is needed to reflect much light, for most of 

 the light passes through the glass; something non-transparent must be behind the glass. In the common mirror it is a 

 mercury amalgam; in the butterfly's silvery scale it is a layer of cavities filled with air. This layer of cavities is not 

 transparent for the same reason that ground glass is not. If we treat the scale with chloroform it has an analogous effect 

 to that of treatiug the back of a common mirror with nitric acid, thus dissolving off the amalgam. In both cases a non- 

 transparent body is converted into a transparent one, and a mirror, which, whatever be the materials of which it is made, 

 if approximately perfect, has a silvery appearance from the amoinit of reflected light, is reduced to a slightly reflecting surface, 

 r.ut let the scale dry again from its bath, as Fischer apparently did not do, and the mirror will again appear. Both silverj' 

 and milk-white colorations are then only optical efl'ects produced by reflected light." 



1 It is greatly to be desiderated that ^ some competent entomologist would give a monographic catalogue of the 

 Lycicnida', in the manner of the late Dr. Stal's ' Enumeratio Hemipterorum,' iu which a key to the whole genera would be 

 given, and in which some principle of variation in nature would be admitted. Our British Museum has a magnificent 

 collection, and its staff of endowed ofticials may ultimately produce this necessary work, for which other students, as a rule, 

 possess neither the time nor material. 



; Named after Mr. Frederick Moore, wlio in coniunctU)n with Dr. Horsfield, published the 'C.at.Lep.Mus.E.I.C.,' and has 

 since written a ' Lepidoptera of Ceylon.' 



5 This figure was taken from a much mutUated specimen, with the taildike appendages to the posterior wings .almost 

 destroyed. 



