1903. Carpenter & Beresford. — Vespa austriaca 6° V- 7'tija. 235 



results from the Discontinuitj^ of Variation." We think that 

 we see here a new species arise b}^ the production, through 

 many generations, of an increasing number of individuals 

 {r7(fa forms) among the offspring, that are markedly unlike 

 the parents {austriaca forms). We believe that austriaca forms 

 give rise to ^tifa forms, but we have no evidence of the reverse 

 process ; and it seems that those specimens of V- rufa varying 

 towards F. austriaca must be regarded as examples of rever- 

 sion towards the ancestral tj^pe. The slight but constant 

 difference between the male armature in our two wasps illus- 

 trates Jordan's ('96) principle of ^' mechanical selection," and 

 supports Romanes' view ('97^ p. 46) that variations affecting the 

 reproductive organs, and tending to prevent intercrossing 

 between an incipient species and its parent form, arise before 

 any striking differences in the general body-structure become 

 developed. These constant differences between the male 

 armature in the two wasps and the absence of intermediate 

 individuals suggest that interbreeding never takes place, and 

 that V' rufa can never be "s-wamped" by crossing with its 

 parent form, V- austriaca. Indeed the latter is now so scarce, 

 that all danger of such -'swamping" is past. Except in Ireland, 

 and possibly in some mountainous continental localities, it 

 has been almost entirel}^ superseded by its more vigorous and. 

 robust descendant. 



References. 



'84. Andre, E.^Species des Hymenopteres d'Europe et d'Algerie. 



vol. ii. Beaune, 18S2-6 (p. 597). 

 '01. Barrington, R. M,, and Moffat, C. K. — Wasps in Co. Wicklow. 



Irish Nat., vol. x.^ 1901, pp. 197-201. 

 '94. BaTESON, W — Materials for the Study of Variatiou. London, 



1894- 

 '99. BuCKi<E, C. W. — Vespa austriaca in Derry and Donegal. Irish Nat., 



vol. viii., 1S99, pp. 163-4. 



'75. Cameron, P.— On some new or little-known British Hymenoptera. 



Proc. Nat. Hist. Soc. Glasgoiu, vol. ii., 1869-75, pp. 304-324. 



