BUTTERFLIES AND MOTHS. 311 



"in proportion to tbe body, it seems probable that the Insect 

 "would more frequently have been struck or pierced in a vital 

 "part, and thus the increased expanse of the wings may have been 

 "indirectly beneficial." 



Display. — The bright colors of many butterflies and of some 

 moths are specially arranged for display, so that they may be 

 readily seen. During the night colors are not visible, and 

 there can be no doubt that the nocturnal moths, taken as a 

 body, are much less gaily decorated than butterflies, all of 

 which are diurnal in their habits. But the moths of certain 

 families, such as the Zygsenidas, several Sphingidse, Uraniidas, 

 some ArctiidsB and Saturniidas, fly about during the day or 

 early evening, and many of these are extremely beautiful, being 

 far brighter colored than the strictly nocturnal kinds. A few 

 ' exceptional cases, however, of bright-colored nocturnal species 

 have been recorded.'* 



There is evidence of another kind in regard to display. But- 

 terflies, as before remarked, elevate their wings when at rest, 

 but whilst basking in the sunshine often alternately raise and 

 depress them, thus exposing both surfaces to full view; and al- 

 though the lower surface is often colored iri an obscure manner 

 as a protection, yet in many species it is as higTily decorated 

 as the upper surface, and sometimes in a very difllerent manner. 

 In some tropical species the lower surface is even more brilliantly 

 colored than the upper.'" In the English fritillaries (Argynnis) 

 the lower surface alone is ornamented with shining silver. Never- 

 theless, 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 en- 

 tomologists 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 butterflies 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 



14 For instance, Lithosia; but Prof. Westwood ('Modern Class, of 

 Insects,' vol. ii. p. 330) seems surprised at this case. On the relative 

 colors of diurnal and nocturnal Lepidoptera, see ibid. pp. 333 and 392; 

 also Harris, 'Treatise on the Insects of Nev^r England,' 1842, p. 315. 



'5 Such differences between the upper and lower surfaces of the wings 

 of several species of Papilio, may be seen in the beautiful plates to 

 Mr. Wallace's 'Memoir on the Papilionidae of the Malayan Region,' 

 m 'Transact. Linn. Soc,' vol. xxv. part i. 1865. 



