78 A.A. Girault: 



fauna; in neighbouring Islands, many species are found common 

 to both while others are dif f erent, yet very similar ; similarity of species 

 is inexplicable unless due to heredity, since the latter is the only cause 

 known to produce fundamental likenesses in nature; mjgration of forms 

 has actually been proved and in modern times has frequently occurred 

 through the conscious or unconscious agency of man; species have a 

 tendency to increase and spread indefinitely; the time for migration 

 to have taken place is certainly abundant as are also the means for it; 

 Islands comparatively near continents appear to have been stocked 

 from the latter, since their fauna resemble more that of the adjoining 

 continent. All facts prove then that genera and species have originated 

 from a common stock at one place. The argument in favor of independent 

 evolutions, namely, that evolutionary factors are the same over the 

 whole earth, breaks down at once when it is remarked that the strongest 

 of these factors, heredity, is the cause of all resemblances and if it 

 were not they would be meaningless for us. 



Correlated with wide geographica! distribution we usually find 

 dom.inance, abundance in numbers of species and much variability 

 and adaptability ; also with large and widespread genera usually 

 some one of the species is dominant, very numerous in individuals 

 and very variable. Trichogramma illustrates this for the genera, 

 T. minutum for the species. Species of large genera, too, are most 

 often very much alike and I have been much surprised at this close 

 resemblance more than once both in Trichogramma and Oligosita. 



None of the genera of this family peculiar to Australia are peculiar 

 to the family, that is, differ more from the genera of other countries 

 than does any genus of the family differ from any other genus. 



10. The Striking Resemblance of Some Australian 

 and North American Species. 



Greater surprise could hardly be produced than was mine when 

 I first saw an Australian Oligosita now named in manuscript. It is 

 so much like the striking North American species sanguinea that I 

 cannot separate them at all in regard to details of structure, nor in 

 details of the brilliant red coloration. The difference between them, 

 however, is as blatant and striking as their close resemblance. It con- 

 sists of a broad and conspicuous white band across the base of the 

 abdomen contrasting with the blood-redness of the body. It so happened 

 that I had already found the species americana in Quensland and 

 consequently was looking for sanguinea, since it appears to be associated 

 with the other species. Thus my surprise was enhanced. In Australia, 

 there also occurs another species which resembles americana very much 

 and I am doubtful as to its validity. The other Australian species so 

 far Seen are not in any way peculiar excepting one, which is characterised 

 by its minuteness, by bearing a median sulcus along the thorax and by 

 being associated with minute yellow mymarids and eulophids in abun- 

 dance upon the foliage of a broad-leafed Eucalyptus in forests. 



