206 f September, 



Geometers and Tineids, enumerated Ly me, nearly all appear durino: 

 cold periods, and, according to my theory, would be liable to perish 

 from cold before depositing their eggs if they were able to leave the 

 food-plant for a lengthened period. Dr. Chapman contends that a 

 female benvmibed with cold would not be able to deposit its eggs. 

 This has not, so far as I am aware, l)een proved at present, but it is 

 known that females moribund from other causes can deposit their 

 eggs, and this is often demonstrated by the behaviour of half dead 

 female insects on the setting board. Dr. Chapman considers that the 

 low temperatures ruling in winter prevent, to a great extent, the 

 emanation of the characteristic odours of plants, and that if winged 

 the females would be unable to find the food-plant. I consider that 

 the wingless condition has been acquired to keep the female on the 

 food-plant, otherwise she might stray away and perish with cold before 

 laying her eggs. This is the essential difference between our two ex- 

 planations, and future experiment and investigation must determine 

 which is correct. 



Mr. Porritt's remarks as to the conveyance through the air of 

 apterous or semi-apterous females by their males are interesting, but 

 unfortunately are not supported by sufficient facts ; tlie balance of 

 evidence, as cited by Dr. Chapman, being in the reverse direction. As 

 already pointed out in my paper, it is I think fairly evident that the 

 disabilities these insects laboiu" under as regards means of dispersal 

 are largely neutralized by the fact that they all feed on very common 

 and widely distributed food-plants, and it is therefore quite conceivable 

 that the needful distribution may be sufficiently effected by the insects 

 crawling from tree to tree, either as larvae, during the summer months, 

 or as perfect females during mild periods in winter. 



I cannot in any way follow Dr. J. H. Wood's views in regard to 

 wingless Geometers. In New Zealand, several species of Geometers 

 with fully developed wings appear during the winter months, and 

 occasionally may be observed resting on tree trunks. The cold here 

 is fairly severe, a temperature of 40 degrees Fahrenheit with drenching 

 rain and hail driven by a fierce southerly gale being often experienced 

 during the months of May, June, July, and Avigust. Yet winter 

 Geometers with ample and flimsy wings occur during those months, 

 and our single species of Hybernia with its semi-apterous female is a 

 great rarity in most parts of New Zealand, although some of the 

 semi-apterous female Tineids are common during July and August. 

 I have observed tlie following species of winged Geometers in fair 



