KACE DIFFERENCES. 251 



insect, while tlio feebler specimens were compelled to 

 content themselves wuth humbler fare. 



This is no purely imaginary case. M. Fabre himself 

 distinguishes three races — or are they species ? — of Leu- 

 cospis which live on the three species of Chalicodomas. 



** Venn du Chalicodome des galets ou des murailles, 

 dont I'opulente larve le sature de nourriture, il merite 

 par sa grosseur le nom le Leucospis gigas, que lui 

 donne Fabricius ; venu du Chalicodome des hangars, il 

 ne merite plus que le nom de Leucosins grandis, que 

 lui octroie Klug. Avec uue ratiou moindre, le geant 

 baisse d'un degre et n'est plus que le grand. Yenu 

 du Chalicodome des avbustes, il baisse encore, et si 

 quelque nomenclateur s'avisait de le qualifier, il 

 n'aurait plus droit qu'au titre de mediocre. 



The Anthrax, again, differs considerably according to 

 the species on which it has fed, those coming from the 

 cocoons of Osmia tricornis being much larger from 

 those from 0. cyanea. 



Or it might well happen that while the victim was 

 from some cause or other, say for instance the absence 

 of food elsewhere, limited to a particular district, the 

 region beyond was suited to the ancestress Sphex. In 

 that case, would she not naturally try whether she 

 could not find some other suitable food ? Tliis again, is 

 not a purely imaginary case. M. Fabre himself tells us 

 that while '•' la Scolie interrompue avait pour gibier aux 

 environs d'Avignon, la larve de I'Anoxie velue {Anoxia 

 villosa). Aux environs de Serignan, dans un sol sablon- 

 neux semblable, sans autre vegetation que quelques 

 maigres gramens, je lui trouve pour vivres I'Anoxie 

 matutinale (Anoxia matutinalls), qui remplace ici la 

 velue," 



