TEE ACTION OF LIGET, ETC. 



371 



of-paradise, etc. — which have a remarkable and 

 hitherto-unexplained tendency to the develop- 

 ment of splendid hues, and which, if not exclu- 

 sively tropical, have their headquarters and pro- 

 duce their largest representatives within the tor- 

 rid zone. Other groups, again, attain their great- 

 est splendor beyond the tropics, e. g., the ducks, 

 the pheasants, and, among insects, the ground- 

 beetles, or Carabidae. It has, indeed, been sug- 

 gested that if the colder regions of the earth are 

 now inferior to the tropical districts in the beauty 

 of their fauna, the cause may be sought in the 

 ravages of the Glacial epoch. If the most mag- 

 nificent species were forest-dwellers, as we now 

 find it to be the case in warm climates, their de- 

 struction would be almost inevitably involved in 

 the desolation of their haunts, and the annihila- 

 tion of their food. Perhaps, too, the very splen- 

 dor of such supposed forms would render them 

 more conspicuous to their enemies, and thus ac- 

 celerate their extirpation. All such speculations, 

 however, are little more than conjectural. We 

 conclude, indeed, judging from the fossil remains 

 of insects discovered at (Eningen and elsewhere 

 (see Quarterly Journal of Science, vii., 255), that 

 certain groups, now mainly tropical or sub-tropi- 

 cal, were very extensively developed in Central 

 Europe ; but at the same time we find indications 

 that the climate, at least as far as warmth is con- 

 cerned, was almost tropical in its character. 



We may next inquire whether the relative 

 brilliance of color in various animal groups is 

 at all connected with their diurnal or nocturnal 

 habits, or with their greater or less exposure to 

 light at different stages of their development. It 

 is a truism that the diurnal Lepidoptera are upon 

 the average much more highly colored than the 

 nocturnal species, the moths. Some weight has 

 been laid on the circumstance that iu butterflies 

 both sides of the wings are freely exposed to 

 light, and that both are also adorned with a vari- 

 ety of hues, while in moths, where the under sur- 

 face of the wings is not turned to the light, it 

 generally exhibits a dull and uniform coloration ; 

 but these facts admit of much qualification. 

 Even among the small number of beetles indig- 

 enous in Britain there are some — such as Ere- 

 bia Cassiope, Coenonyrnpha Davits, and Thanaos 

 Tages — certainly less brightly colored than many 

 moths. Many species of butterflies, also, if rich- 

 ly colored on the upper surface of the wing3, can 

 boast no gay or varied tints beneath. We need 

 only mention the common peacock (Vanessa lo). 

 Again, in certain genera of moths we find colors 

 as vivid as can be met with in butterflies — e. g., 



Callimorpha, Euchelia, Chelonia, and Catocala. 

 The most remarkable feature in these genera is 

 that the chief display of color appears on the 

 upper surface of the hind-wings — a part as lit- 

 tle exposed to light as the lower surface, since 

 when the insect is at rest, in the daytime, it 

 is completely screened by the anterior pair of 

 wings. 



In the larva state it cannot be said that Lepi- 

 dopterous insects are much exposed to light. As 

 a rule the caterpillars of the diurnal as well as 

 of the nocturnal species prefer shade to sunshine. 

 It is perhaps somewhat curious that the habits 

 of the larva stand in no regular connection with 

 the diurnal or nocturnal character of the mature 

 insect. 



Turning to the Coleoptera, we find further 

 facts unfavorable to the supposed predomi- 

 nant influence of light upon the development 

 of color. Such Coleopterous larvae — and they 

 are the majority — as live in total darkness are, 

 indeed, generally of a dull, dirty gray, con- 

 trasting strongly with caterpillars which are 

 more or less exposed to light, and many of 

 which exhibit a bright and pleasing coloration. 

 This circumstance, like the etiolation of plants 

 reared up in darkness, is certainly in favor of the 

 view that light is not without influence upon or- 

 ganic coloration ; but, on the other hand, let us 

 consider the after-life of some of these dull-look- 

 ing beetle-grubs. The most gorgeous, perhaps, 

 of all Coleoptera are the Buprestidae. These 

 creatures spend the whole of their larval and 

 pupal life within the trunks of trees, and conse- 

 quently in total darkness. When mature, in- 

 deed, they sport for a time in the checkered sun- 

 light of the woodlands. But why, if light be the 

 main cause of animal coloration, should they be 

 so far superior in brilliance to the Longicornes, 

 or wood-beetles, which from birth to death are 

 exposed to precisely the same circumstances ? 

 Taking the opposite extreme, the Staphylinidae — 

 of which the common " devil's coach-horse" is a 

 familiar example — rank in appearance among the 

 dullest and least decorated of all the insect 

 tribes, whether they inhabit cold or warm cli- 

 mates ; yet these creatures, instead of leading 

 the earlier part of their life in complete and con- 

 stant darkness, are active when larvae, and may 

 be seen running about in the daylight, seeking 

 for prey. Surely, therefore, bein^r so much more 

 exposed to light than the Buprestidae or the Ce- 

 toniadae, they ought, on the theory we are exam- 

 ining, to be at least correspondingly beautiful. 

 Let us turn to the Melolonthidae, of which the 



