376 Mr. T. V. Wollaston on the Tarplui. 



same or contiguous tracts, almost every extensive assemblage has a 

 few exponents which are apparently quite indigenous in regions ex- 

 ceedingly remote from that which sustains the major part or 

 nucleus. 



Now Tarphms is exactly in this predicament. Centred in the 

 damp and often almost inaccessible forests and elevated Serras of 

 the Atlantic islands, off the north-western coast of Africa, the 

 various species are so sluggish in their habits, and so locally re- 

 stricted, that but few of them have succeeded in tenanting more 

 than a very small area — being frequently confined to a single 

 ravine, or an isolated mountain-slope. And so adapted do they seem 

 to be to those dense humid regions (where, as just stated, they may 

 be found attached to the sticks and fragments of wet, decaying wood 

 which strew the ground beneath trees of a fabulous age), and so 

 unable to exist in arid spots of a lower altitude, that it is impossible 

 to resist the conviction that no process of ordinary migration can 

 have ever brought them to where they now are, and that they con- 

 sequently occupy, even to this day, their actual primeval sites. As 

 might be expected from this epitome of their modus vivendi, nearly 

 every one of these islands in which the laurels still remain has its own 

 Tarphii, — merely two species out of the twenty-eight hitherto dis- 

 covered (namely, the T.Lowei, at the Madeiras, and the T.canariemis, 

 at the Canaries) having apparently colonized more than a small portion 

 of even their respective groups. If, then, these insects are so circum- 

 scribed in their several ranges, and so difficult of dispersion (whether 

 by their own means or casual ones) that they have not only failed 

 to establish themselves in the various parts of their little archipela- 

 goes, but have not extended over even their peculiar islands — where, 

 in both instances, all the conditions arc present, and comparatively 

 close at hand, which their necessities require, — it seems preposterous 

 to conclude that the representative from so distant a country as 

 Sicily can have belonged to the same community as its Atlantic 

 allies. Yet, if the desire of naturalists to maintain a hopeless thesis 

 should drive them still to that almost incomprehensible conclusion, 

 I may add that, despite the close resemblance of this Sicilian Tar- 

 phius to the Madeiran and Canarian ones — so close that they must 

 needs be regarded as undoubted members of the same genus, — there 

 is nevertheless sufficient difference between them to warrant the 

 conviction (even in those who believe in the possible existence, Avith- 

 in reasonable limits, of geographical sub-species, occasioned by the 

 long-sustained action of surrounding influences) that they cannot 

 have proceeded from the same stock. So that, whether viewed geo- 



