LACHNEIDES. 447 



clinging to the place on which she had so carefully arranged them. 

 The posture, the colour, the brown band, even the white spot 

 harmonized in so extraordinary and unexpected a manner with its 

 position and surroundings that even after the creature was discovered 

 he was amazed at the deception. 



With one exception, the much- vexed question of the specific identity 

 of Lasiocampa quercus and L. callunae, the British species of this super- 

 family are well-defined, and, as may be expected from the great geographi- 

 cal range of most of these insects, they offer considerable variation, 

 but possibly the variation in the habits of a widely distributed species 

 in its earlier stages is as interesting as the variation in the appearance 

 of the imago, and it is this difference of habit that has led to the 

 suggestion that L. callunae is specifically distinct from L. quercus, 

 although it is not generally known that Trichiura crataegi and its var. 

 ariac offer an almost parallel instance of racial habits being exhibited 

 throughout the whole period of the insects' existence, and we have in 

 those species an excellent illustration of how isolation by diverse 

 habits may aid in the differentiation of species from a common stock, 

 whilst it is evident that the racial peculiarities of L. quercus and callunae 

 and T. crataegi and ariae have gone far towards the necessary point, 

 although they have not yet reached it by becoming thoroughly 

 differentiated. In Scotland, and on the high-lying moors of England, 

 Ireland, and Wales, the imagines of L. quercus emerge in June (or 

 thereabouts), lay their eggs, the larvse hatch out, and feed up to about 

 the third stadium 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 callunae there are occasional individuals that emerge 

 from the cocoon in the August of the same year in which the larva; 

 have pupated, and thus only take one year instead of two for their 

 ecdyses. Throughout France, and reaching well up into England as 

 far as Yorkshire, in the lowlying parts of the country, imagines of L. 

 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 L. 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 callunae. Thus in one brood it is possible to get part with 

 the habits of one form and part with the habits of the other. In the 

 cold season of 1888, almost all larvae of L. 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 callunae 

 habit at once under unfavourable conditions. It appears that in 

 the southern lowlying districts 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 France all are 

 L. quercus, and have the quercus habit. In the mountains of France 

 and Piedmont we have found the larvae at considerable elevations, and 

 here the callunae habit again prevails. 



