10 



from a common stock. It is evident that, in the case under review, 

 Z. quercus and L. callunce have gone far towards the necessary point, 

 although in my opinion they have not yet reached it by becoming 

 thoroughly differentiated. In Scotland, on the moors of North 

 England, Wales, Ireland, and the south of England, the perfect 

 insect emerges in June (or thereabouts), lays its eggs, the larvae 

 hatch out, and feed up to about the third skin before hybernation ; 

 they subsequently feed up slowly the next summer, pupate in July 

 or August, go over the winter in the pupal stage, and finally emerge 

 in the following June as imagines, having taken two years to complete 

 their metamorphoses ; but among these two-year calhmce there are 

 occasional individuals that emerge from the cocoon in the August 

 of the same year in which the larvae have pupated, and thus only 

 take one year instead of two for their ecdyst s. Throughout France, 

 and reaching well up into England as far as Yorkshire, in the low- 

 lying parts of the country, imagines of Z. quercus emerge in July 

 and August, lay their eggs, larvae from which hybernate comparatively 

 small, but feed up quickly in the spring, pupate in May and June, 

 and emerge in July and August of the same year. These are the 

 normal habits of Z. quercus ; but among the many that do this an 

 occasional individual remains in cocoon the whole winter, and does 

 not emerge until the next summer, thus taking on the habits of 

 callunce. Thus in one brood it is possible to get part with the habits 

 of one and part with the habits of the other. In the cold season of 

 1888 almost all larvae of Z. quercus collected in Kent continued to 

 feed throughout the cold summer until August, then pupated, and 

 went over the winter in this stage, adopting the callunce habit at once 

 under unfavourable conditions. It appears to me that in the south 

 the percentage of individuals that go over is a small one, but 

 gradually increases as we go north (or reach a higher altitude), until, 

 when we reach the Highlands of Scotland (or the hill-moorlands), 

 the individuals have a fixed habit, requiring two years to come to 

 maturity. In the warm parts of South France all are Z. quercus, 

 and have the quercus habit. In the mountains of France and Pied- 

 mont I have found the larvae at considerable elevations, and here 

 the calhmce habit again prevails. 



An attempt to discuss the peculiarities of each separate species 

 would occupy far too much time. I will only add a few notes on 

 three of the other species. 



Malacosoma castrensis is an exceedingly local species. It was 

 reported from Devonshire many years ago, and although it does not 

 appear to have been found there of recent years, there is no proof 

 that the species does not still occur there. On the Continent it 

 occurs all over Central Europe, swarming in some districts on weedy 

 waste places, often found high on the mountains, in pine woods, and 

 various localities of different situation and aspect. In Britain it is 

 supposed to be confined to the coast of Suffolk, Essex, and Kent, 

 and probably ninety-nine hundredths of the specimens bred and 



