116 THE CAUSES WHICH PROPAGATE 



would, when disturbed^ partially expand her wings, and at the 

 same time was produced a grating sound, which seemed to come 

 from the base of the wings. •'^ 



This braving our winter^s climate is no chance occurrence, 

 but is almost yearly observed with regard to the Peacock or the 

 Tortoiseshells, and shows a remarkable accommodation of habit 

 and persistence of species, when we consider two of this genus 

 find their limit of northward distribution in the Cheviots. 

 Doubleday describes the fallen boughs of the forest covered with 

 protective horse-shoe fungi as their origuial winter quarter of the 

 Palrearctic areas. " Last winter,'''' he says, " some large stacks of 

 beech fagots, which had been loosely stacked up in our forest 

 (Epping) the preceding spring with the dead leaves adhering 

 to them, were taken down and carted away, and among these 

 were many scores of V. lo, and of the Tortoiseshells, Urticoe and 

 Pol^chloros." 



It may be conjectured that beneath pure Italian skies the 

 portion of the year passed by these butterflies in hybernation 

 would be brief; but in more northern countries the few species 

 that gladden the landscape shrink from encountering the first 

 visits of the benumbing airs of winter. I took advantage of a 

 singular opportunity thus afforded, during a sojourn in the 

 Highlands, to investigate the capability of the Small Tortoise- 

 shell Butterfly for stridulation. On the 22nd of August, a dull 

 day, when there had been a sudden fall in the temperature, a 

 fresh brood of the Nettle Butterflies, newly sunning themselves 

 at West Loch Tarbert, hastened in from the fields to shelter and 

 remain torpid, perchance to dream. I detached one of these, a 

 female, hanging on cobwebs in an outhouse, and seated her, still 

 drowsy, on the palm of my hand. Then, with the other hand, 

 touching lightly the tails of the hind wings, I induced her to 

 depress and shut the wings successively. Each time she testily 

 performed this action I heard distinctly, as the fore-wings were 

 brought forward, when only the extreme basal portion of the 

 wings was in contact, a sound soft and refreshing, like evening 

 footsteps on the pavement, or grating sand-paper. 



In the Small Tortoiseshell, then, certainly, and in the 

 Peacock more than probably, it will be noticed, the sound 

 produced by the vexed insect must have arisen from the friction 



