Geographische Verbreitung, ßeisen. 197 



wysus vitikollis and its var. longiilus), one of which bores out the stems of a 

 lii<hus, while the other burrows under the bark of a forest tree {Bohea). Close 

 and exclusive attachment to such different phvnts must isolate them nearly as 

 much as would the presence of a geographica! barrier. 



The extreme variability in colour and structure of many of the insects and 

 niollusca, the great indefiniteness of many forms, might be thought to be due to 

 the absence or slackness of the selecting agencies which in other lands 

 elirainate the unfit. Perkins inclines to the opinion that some other cause 

 — possibly lack of time in which to become defined as distinct species — 

 must account for this. Some of the very species that vavy most form a large 

 ]iart of the food of the endemic insectivorous birds, and must therefore have 

 been subjected to rigorous selection: so that "it would appear (he writes) either 

 that this selection has been singularly ineffective in producing uniformity of ap- 

 pearance in a species, or that the very great variability must be itself advanta- 

 geous". When a species is exceptionally wide-ranging and variable it is frequently 

 found that there are certain others, much rarer and less wide-spread, very closely 

 allied to it: these are probably "offshoots"' from it. Some interesting cases of 

 discontinuous Variation are also mentioned (p. 70). 



One more phenomenon (and one already mentioned) must be noticed — 

 that is, reduction or loss of the organs of flight. A most interesting section 

 is given (p. 48) on the flightless genera and species of insects. In many cases the 

 loss of the power of flight has probably occurred within the Islands, many en- 

 demic flightless genera being closely allied to, and probably derived from, en- 

 demic fully-winged genera. But some large flightless groups are so isolated in 

 structure that it cannot be known whether the original Immigrant forms from 

 which they are descended were fully-winged or flightless: e. g., the extraordinary 

 flightless Coleojiterous family Proterhinidae, represented by 136 endemic 

 species, and only known from elsewhere by a Single specimen from Samoa. 

 Perkins considers that all the cases of flightlessness are to be explained by 

 disuse of the organs of flight, not that these organs have been reduced by 

 natural selection owing to the danger of their possessors being blown out to sea. 

 Only in one case could this latter theory possibly be applied — the case of a 

 wingless moth, which is however closely related to fully-winged forms some of 

 which flourish in wind-swept localities near the sea. Species dimorphic in this 

 respect — that is containing both fully-winged and flightless individuals — are 

 very rare. 



The more general part of the essay is followed by a series of separate 

 reviews on different groups, Hymenoptera, Lepidoptera etc. With these it is 

 outside the scope of this abstract to deal. It is only hoped that what has been 

 written here may convey some slight notion of the highly suggestive nature of 

 Perkins' essay, and of the extraordinary interest of this unique fauna. 



Scott. 



530) Kobelt, W., Der Schwanbeimer Wald. IV. Landschaftlicbes. In: 44. Ber. 

 Senckenberg. Naturf. Ges., S. 236—265, 12 Abb., 1913. 



In diesem Scblußkapitel bringt K. noch einige Nachträge zur Fauna des Gebietes. 

 Nach Guide finden sieb hier eine Anzahl von Vertretern der pontisch-sarmatischen 

 Steppenfauna. Für die Wanzen Cainptotelus costatus H. S., Dimorphopterus spinolae Sign, 

 und Dercphysia foliacea Fall. var. biroi How. ist der Schwanbeimer Wald der einzige 

 deutsche Fundort. Ferner kommen hier vor Chorosoma schillingi Schm. und die Penta- 

 tomide Carpocoris lunulatus Goeze sowie die seltenen Geradflügler Sphingonotus cyano- 

 pterum Chpr., Phaneroptera falcata Scop. und Caloptenus italicus L. Loeser. 



