INSECTS. 357 



alone is ornamented with shining silver. Nevertheless, as 

 a general rule, the upper surface, which is probably more 

 fully exposed, is colored more brightly and diversely than 

 the lower. Hence the lower surface generally affords to 

 entomologists the more useful character for detecting the 

 affinities of the various species. Fritz Miiller informs me 

 that three species of Castnia are found near his house in 

 S. Brazil; of two of them the hind wings are obscure, and 

 are always covered by the front wings when these butter- 

 flies are at rest; but the third species has black hind wings, 

 beautifully spotted with red and white, and these are fully 

 expanded and displayed whenever the butterfly rests. Other 

 such cases could be added. 



If we now turn to the enormous group of moths which, 

 as I hear from Mr. Stainton, do not habitually expose the 

 under surface of their wings to full view, we find this side 

 very rarely colored with a brightness greater than, or even 

 equal to, that of the upper side. Some exceptions to the 

 rule, either real or apparent, must be noticed, as the case of 

 Hypopyra.* Mr. Trimen informs me that in Guenee's 

 great work three moths are figured, in which the under sur- 

 face is much the more brilliant. For instance, in the Aus- 

 tralian Gastrophora the upper surface of the fore wing is 

 pale grayish-ochreous, while the lower surface is magnifi- 

 cently ornamented by an ocellus of cobalt-blue, placed in 

 the midst of a black mark, surrounded by orange-yellow, 

 and this by bluish-white. But the habits of these three 

 moths are unknown; so that no explanation can be given 

 of their unusual style of coloring. Mr. Trimen also 

 informs me that the lower surface of the wings in certain 

 other Geometrae f and quadrifid Noctuae are either more 

 variegated or more brightly-colored than the upper surface; 

 but some of these species have the habit of " holding their 

 wings quite erect over their backs, retaining them in this 

 position for a considerable time," and thus exposing the 

 under surface to view. Other species, when settled on the 

 ground or herbage, now and then suddenly and slightly lift 



*See Mr. Wormald on this motli ; " Proc. Ent. Soc.," March 2, 

 1868. 



f See also an account of the South American genus Erateina (one 

 of the Geometrae) in "Transact. Ent. Soc," new series, vol. v, pis 

 X.V and xvi. 



