90 



less, with the knowledge hoth of the modifyiiig effects of 

 isolation, and also of the kind of modification essentially 

 peculiar to that island, I am perfectly satisfied that it is 

 a mere local state, although a very remarkable one, and 

 has no claim whatsoever to be otherwise considered*." 

 The Pecteropus Maderensis, Woll., is of a greenish- 

 brassy tinge in Porto Santo, and much acuminated in 

 front; whereas on the Dezerta Grande it is almost 

 invariably coppery, and less narrowed anteriorly. The 

 Caulotrupis lucifugus, WoU., although ranging through 

 no very opposite phases, either of outline or sculpture, 

 " appears to possess a slight modification for every 

 island of the Madeiran Group : and hence small shades 

 of difference, which might otherwise be regarded as 

 trifling, become directly important, and cannot be 

 ignored in a local fauna, — even though a general col- 

 lector may deem it unnecessary to recognize them. In 

 real fact, however, such distinctions, when viewed geo- 

 graphically, are of the greatest interest, as serving to 

 illustrate what we have so often had occasion to com- 

 ment upon, namely the influence of isolation and other 

 circumstances on external insect formf." The Psyl- 

 liodes vehemens, Woll., is permanently paler in Porto 

 Santo than it is in Madeira proper, being almost entirely 

 testaceous. "That the species is identical, however, 

 with the Madeiran one I have not the slightest doubt, — 

 the sculpture and colour, as I conceive, having merely 

 imdergone a change since the remote period of its isola- 

 * Insecta Maderensia, p. 36. t Id. p. 310. 



