78 J. W. SLATER, ESQ., F.C.S., P.E.S., ON 



have their beginning in regions of tropical heat which generate 

 alike multitudes of harmless creatures, and at the same time give 

 birth and development to their numerous natural destroyers, a 

 counterpoise to the too rapid or excessive preponderance of any in- 

 dividual species being thereby effected. The parasitic lianas, and 

 other creepers which surround with their deadly embrace the 

 towering forest tree, and by degrees strangling all vitality in their 

 supporter, hasten on its decay, and ultimately themselves come to 

 an end together with the fall of the dead trunk, giant serpents, 

 huge and venomous spiders, centipedes, aud scorpions, etc. These 

 are altogether wanting in temperate regions of our globe; and 

 in Iceland no reptile of any description is to be met with, the most 

 common of our small British centipedes occurs very rarely, while 

 the circumstance of the Arachnid a only comprising ground spiders, 

 and very few (and I am not certain that there are any at all there) 

 that construct webs, tends to numbers of flies and moths that would 

 otherwise come to an end, being preserved. 



Climate and isolation are the two factors we have to take account 

 of in a review of the "struggle for existence" in ''Ultima Thule." 

 To take the second of these two circumstances first, its isolation at 

 a distance of 500 miles from the north coast of Scotland, renders 

 the chance of any new species of insect visiting its lonely wastes, 

 almost, if not altogether, an impossibility. Supposing, for argu- 

 ment's sake that during the short island summer of 10 or 12 weeks 

 an insect was imported by the periodical voyage of the Danish 

 steamer, having settled on the vessel before it left the port of 

 Copenhagen (as a solitary Painted Lady V. Cardui) was reported 

 on reliable authority to have been seen in Shore Street, Reyhjavik, 

 in the summer of 1888) the chances of its perpetuation and con- 

 tinuance are even more infmitesimal than those of its arrival. The 

 food plants of the larvseof mostof our common butterflies either do not 

 occur at all in Iceland, as for example the oak and the elm, or are very 

 rare and local as the nettle and thistle, or are very scantily cultivated, 

 as the cabbage and turnip. Any English species of butterfly more- 

 over would be seriously, if not altogether handicapped in the struggle 

 for existence in consequence of the fact that as all the so-called 

 Icelandic forest consists of dwarf scrub, willow and birch, there is 

 no hollow tree trunk wherein the imago can safely hybernate, or 

 sheltered place whereon the pupa can hangup during the inclement 

 weather. The actual severity of the climate, which, by the way, 

 varies considerably in different parts of the Island, is not the only 

 enemy to be reckoned with, but the fact of unavoidable exposure 

 to its storms of wind, rain, aud snow as well. The larvseof several 

 moths on the contrary, which occur in Iceland seek a refuge under 

 ground preparatory to undergoing their change into the pupa state, 

 and are thereby preserved from any ill-effects consecpient on 



" The dreadful pother o'er their heads/' 



