490 



McNeill 



South Seymour) lying so near larger ones that they may be 

 regarded as forming an integral part of them. The number 

 of known species is twenty-six. This number includes six 

 species which are almost certainly cosmopolitan, but excludes 

 the doubtful Vates and Gry litis given in Scudder's List. 



The Hopkins Stanford Expedition, as is obvious, has greatly 

 enlarged our knowledge of the orthopterous fauna of these 

 Islands. But it has done more. By collecting a large series 

 of individuals of the several species it has shown how potent a 

 factor isolation is in the production of species. This example 

 is especially instructive because the differentiation cannot well 

 be explained by natural selection, or by the effect of environ- 

 ment. All the indigenous species are apparently new. Of 

 these 20 indigenous species twelve are incapable of flight. Of 

 the remaining eight, one, G. solllaria, has a wingless female ; 

 another, Gryllus galapageius^ is wingless twice as often as 

 winged. Thus nearly seventy per cent, of the native orthoptera 

 are wingless. 



Of the native species nine, including the cockroach, mantis, 

 crickets, and the Liparoscelis were in all probability brought 

 to the islands on timber or in partially decayed logs, the Man- 

 tid, at least, in the egg state. Though nothing is known of 

 Halmentis^ yet judging from some of its allies, this species 

 may have been introduced in the Q.gg state, the eggs being de- 

 posited in partly decayed or at least dead timber. The Schis- 

 tocera and the Sfhingonotus were almost certainly brought 

 there by their own wings, and it seems probable that the long- 

 winged Desmopleura was introduced in the same way. As to 

 the four remaining species there is greater uncertainty. Both 

 Anaulocomera and Conocephalus have efficient wings but 

 neither are great flyers and it seems very unlikely that they 

 should have been able to keep on the wing long enough to 

 reach the islands. Nor can we readily suppose that they could 

 have drifted in tree tops, since their wings would have tempted 

 them to fly, probably thus ruining their only chance for safety. 

 All things considered, the most reasonable hypothesis is that 

 they were introduced in the Qgg state, the eggs being attached 

 to twigs or leaves. 



