6 INSECTA MADERENSIA. 



edges of the Cui-ral das Freiras, and on the northern limits of the Paul da Serra, 

 — near the extreme head of the Ptibcii'o do Inferno ; and it has been, likewise, 

 captured by Mr. Kousset on the Pico d'An'ibentao, above Fimchal. It is an 

 insect of wide Em-ojiean distribution, ranging from Lapland to the Mediterranean 

 shores; and, licnce, its comparative rarity in oiu* island group would seem to 

 imply that it has there reached, in aU probability, one of its most southern loca- 

 tions, — an hypothesis which the consideration that, whUe in higher latitudes it is 

 confined mainly to the lowest elevations, its normal Madciran limits are apjoarently 

 from about 1500 to 6000 feet above the sea, would go far to corroborate. By a 

 reference to the above diagnosis, it will l)e seen that the typical European state of 

 the D. sigma does not occur at all in Madeu'a proper, l)ut only in Porto Santo. 

 True it is that the modifications in the several islands present but slight diS'er- 

 ences inter se ; nevertheless, being constant, I would lay particular stress upon 

 them, since they go very materially to prove that the effects of isolation on 

 external insect form are even more important, if possible, than those of latitude. 

 That this is the case, in the present instance, appears clear from facts so minute 

 as these. Por, out of the many specimens which have come under my observation 

 from various countries of Europe, if there is one point more constant than another 

 in this otherwise A^ariable species, it is, I believe, vmder all circumstances, its im- 

 maculate prothorax. Now while this, we may almost say essential, character 

 obtains ia Porto Santo, in Madeii'a it does not hold good : the prothorax there is 

 invariably infuscate in the centre ; and on a small adjacent rock it is entii'ely dark. 

 Nor let any one suppose that details apparently so trivial are beneath oui' notice, 

 or the mere result of chance, since it is by the observation of such-like points, and 

 by marking theu* development according to the cu'cumstances of the several lo- 

 calities in which they obtain, that we arc alone able to appreciate thcii' importance, 

 and so to form, in a A\'idcr and geographical sense, a correct estimate of theii" 

 value. 



5. Dromius arenicolus, WoU. 

 D. latus ater nitidus, elytris substriatis, lateribus, gutta elongata obliqua humcrali fasciaquc trans- 

 versa, subapicali pallidis, tibiis tarsisquc piceis. 

 Long. Corp. lin. 1^—2. 



Habitat sub lajjidibus in locis arenosis Portus Sancti, prsesertim per cram maritimam, tempore vernali 

 \'ulgatissimus. 



D. broad, deep black, shining, sometimes with an obscure seneous tinge. Head broad. Prothorax 

 short, subcordatc, much narrowed behind. Ehjtra rather faintly striated, with the lateral 

 margin, an elongated obhque humeral \itta or stria (confluent with it), and a transverse fascia a 

 little before the apex, very pale testaceous. Wings obsolete. Tibite and tarsi piceous. The pale 

 jiortions of the elytra are sometimes indistinct, though never absent ; and occasionally they are 

 altogether confluent. 



