362 Mr. T. Vernon Wollaston on 



XXV. On the Atlantic Cossonides. By T. Vernon Wol- 

 laston, Esq., M.A., F.L.S., &c. 



[Read Feb. 4th, 1861.] 



I PROPOSE, in this paper, to lay before the Entomological Society 

 an enumeration of all the members of the Rhynchophorous sub- 

 family Cossonides which have hitherto been detected in the 

 Atlantic islands ; and it will be perceived, by a glance at the 

 following pages, that no less than forty of them have, up to the 

 present date, been discovered in those various oceanic groups. 

 But, as neither the Azorean archipelago nor that of the Cape de 

 Verdes have as yet been investigated, it is certain that many 

 additions will eventually be brought to light. In St. Helena, too, 

 it is far from unlikely that others will be found — particularly 

 of the anomalous genus Microxylohius, of which six exponents are 

 recorded below. From the Madeiras, which have been now so 

 carefully explored, and in which as many as nineteen of these 

 Xylophagous Curculios have already been observed, we cannot 

 expect much further material ; whilst the fifteen Canarians may 

 be safely regarded as a near approximation to the entire number 

 inhabiting the neighbouring archipelago. The single species from 

 Ascension, as will be gathered from the remarks, is perhaps a 

 mere accidental importation into that island ; though its close 

 affinity with the Mesoxeni, and the fact of its being absolutely 

 congeneric with the British Pentar thrum, would render it at all 

 events probable that the insect is essentially an Atlantic one. 



Touching the Madeiran and Canarian groups, of which alone 

 I feel enabled to speak with any amount of precision, no one who 

 has laboured in them practically can have failed to be struck with 

 the important part which the Cossonides play in the several 

 districts and altitudes of those mountain-islands. Whether in 

 the few sylvan regions which still remain (and where a large 

 proportion of them do the work of destruction amongst the mag- 

 nificent Laurels which so eminently characterize the Atlantic 

 flora), or whether on the exposed rocky slopes (where the 

 gigantic Euphorbias nourish a fauna of their own, and the stalks 

 of shrubby plants afford unfailing sustenance for these Riiynco- 

 phorous borers), or even beneath stones on the open serras of a 

 lofty elevation, we find them strangely ))re(loniinant, and oc- 

 casionally in such profusion (though individually rather than 

 specifically) that the various rotten stems appear to be almost 

 alive with them. 



