318 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



CONCLUDING REMARKS 



The fauna under consideration is oceanic in its character; 

 very few of the species are wholly tropical, but are also repre- 

 sented in the more temperate regions (where they occur as 

 stragglers or as well established insects) by the identical spe- 

 cies, or the one from which they were probably derived. That 

 this fauna, inhabiting islands situated on the equator, is not 

 typically tropical, is quite to be expected, since the climate of 

 the Galapagos cannot be termed tropical but rather temperate ; 

 with much aridity, that would suggest the survival of the fittest, 

 the immigration largely of migratory forms which de natura 

 must be hardy, and the elimination of more delicate and fastid- 

 ious species which were not perpetuated there owing to the 

 climate, enemies, or lack of food-plant, for it is not improb- 

 able that some fragile species once reached the Galapagos 

 Archipelago. 



With the possible exception of the Lycsenid, Cupido parrha- 

 sioides, the rest of the species treated here are strong fliers and 

 hardy insects, and some, as Callidryas eubule and Deilephila 

 lineata, are widely distributed and of migratory habits, Phleg- 

 athontius cingulata having been caught at sea 500 miles from 

 the nearest land (Holland). 



An island of continental origin, whose fauna has not been 

 once obliterated by some catastrophe, would contain a com- 

 paratively large number of species, since in this case there 

 would have been no water for the species to cross over, and 

 barring a change of climate and a long period thereafter, the 

 flora would remain about the same as that of the mainland 

 from which it was separated, and at least a goodly number of 

 the insects would persist, whereas we have seen that the insect 

 fauna of the Galapagos is very scant. The mainland, whether 

 we consider the Mexican, Isthmian, or South American region, 

 is undoubtedly very rich in Lepidoptera, as compared with that 

 order as represented in the Galapagos. 



The inferior size of a number of the Galapagos Lepidoptera 

 as compared with the same species on the mainland, suggests 

 that the climate is largely responsible for this change ; and the 

 fact that in some cases they are subspecifically or specifically 



