Cifleoj'tcra of ihc Madeira Islaiuh. G91 



tativcs of the same species in Europe or elsewhere. If it 

 were true that all the Madeira inseets (exceptinj^ those 

 introduced by man) had arrived by flight, ue should have 

 to assume that the many flightless beetles had descended 

 from ancestoi's with unusually strong Hying powers, the 

 dis^tance between the Madeiras aud the mainland beiug nearly 

 400 miles. One has only to contemplate these beetles {e.g., 

 many of the characteristic Tenebrionidse) to see that this 

 cannot well be the case. In Porto Santo 1 found the large 

 Blaps gages, L. (or gigcis^ supposing gages to have been a 

 misprint), said to be the bulkiest of all the Madeira Is. 

 beetles. It has the elytra fused together, and thus was 

 chosen as a typical example to illustrate Darwin's theory, in 

 the exhibit at the British Museum (Natural Plistory), at the 

 time of the Darwin Celebration in 1909. Its distribution 

 on the Madeira and Canary Islands, and even the remote 

 Grand Salvage, is remarkable enough, but the very same 

 species occurs on the mainland, in Europe and Morocco. 

 As a matter of fact, we must doubtless suppose that the 

 ancestors of many of the endemic types of beetles reached 

 the islands on floating trees and similar objects, a few per- 

 haps on the bodies of birds. In this process there would 

 be a strong selective influence; the sedentary or apterous 

 insects would hold on, while more volatile forms would 

 leave their support and perish in the sea. The total absence 

 of Cicindelid^e could thus be explained. These animals are 

 incapable of sustained flight, but also extremely restless. 

 They could neither arrive on the wing nor remain on the 

 most favourable raft. Natural selection might thus account 

 for a preponderance of small and apterous species, in a 

 manner not contemplated by Darwin's theory. Once such 

 sedentary or flightless species had arrived, they would 

 gradually spread, and because of their habits more easily 

 break up into segregates, isolated in different districts or 

 small islands. Thus the Madeira Islands present a long 

 series of perfectly apterous Helojjs, some living only in 

 Madeira, some confined to Porto Santo. In the Desertas, 

 which appear to have been formerly united with Madeira, 

 are three species of Helops, all common to Madeira, but not 

 found in Porto Santo. But it is interesting to find that 

 one of these species, H. vulcanus, AVollaston, is on the 

 Desertas (Chao and Deserta Grande) slightly wider and 

 larger, with the prothorax distinctly modified. As Wollaston 

 calls this var. a, it must stand as typical vulcanus in nomen- 

 clature, and his var. S, from Madeira, mav be called var. or 



15^ 



