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less, with the knowledge both of the modifying 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, Woll., 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 

 undergone a change since the remote period of its isola- 

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



