﻿TOUR ON THE TABLE-LAND OP MOUNT ARTHUR. 55 



gleam of sunshine would enable the black insect to dry its wings, 

 fly away, and propagate its species before the white one was nearly 

 developed, and consequently there would be a continual selection 

 in favour of the darkest varieties. This theory, I believe, is the true 

 explanation of the singular prevalence of melanic species at high 

 elevations, and may of course be equally well applied to those 

 dark varieties and species of insects which have, hitherto, been 

 almost invariably taken in the arctic regions. That there is a 

 marked tendency to a darker coloration in the Lepidoptera from 

 the Mount Arthur district as we ascend in altitude, I do not 

 think anyone can for a moment dispute, who examines the 

 representative collection now before the Society. 



For those wishing to learn further particulars in connection 

 with this most interesting subject, I must refer them to the 

 abstract of Lord Walsingham's paper contained in the 'Entomo- 

 logist' (Entorn. xviii. 81). 



In conclusion, I should like to give a very striking instance 

 of protective colouring, which I observed when on a previous 

 visit to the Table-land in 1888. While gathering some small 

 branches from a birch tree, I discovered a beautifully variegated 

 larva imitating exactly the delicate hues of the lichen-covered 

 twigs. After feeding on the birch leaves for a few days it spun 

 up, and emerged a very grey form of Declana roccoce on June 7th. 

 I have often seen the larva of this insect, as before mentioned 

 (' Transactions,' N.Z., p. 190, 1888), round Wellington, where, 

 however, it does not in the least resemble the curious caterpillar 

 found on the table-land. This circumstance, I think, gives us a 

 hint as to the means by which alpine insects may have assumed 

 some of their peculiarities. 



In connection with my previous visit to the table-land in 

 1888, I should also mention that it was three weeks later in the 

 year than in 1889, and I noticed great differences in the insects 

 observed. For instance, in February, 1888, Stathmonyma anceps 

 was very abundant ; Erebia pluto, scarce ; Rhyssa antipodum, one 

 taken and three or four seen; Cladopais mirus, very common. In 

 January, 1889, 1 found S. anceps was rare, E. pluto very abundant, 

 and of R. antipodum and C. mirus I neither saw or captured a 

 single specimen. This shows that there is a rapid succession of 

 insect life on the mountains, which can only be properly studied 

 by numerous and prolonged visits of entomologists. 



Wellington, New .Zealand. 



