74 BRITISH LEPIDOPTERA. 



horn dark brown or black, tipped with white, with two short 

 dark oblique stripes joining the base of it. Head, abdomen and 

 prolegs varying according to the colour of the body, thoracic legs 

 pale flesh colour ; stigmata brownish-yellow bordered with black, but 

 variable. James notes one nearly black larva at Deal, one brown and 

 two green ones at Rickmansworth.. one dark brown one at Broxbourne, 

 and Russell records that larvae taken on the banks of the Basingstoke 

 canal from water-bedstraw were in various stages, some nearly fullfed, 

 others very small; half of them were green in colour (the small ones) 

 and half black. In confinement all the green ones in moulting changed 

 to black and pupated when of that colour. Hammond describes 

 (Ent., xiii., p. 280) a form of the larva as : Light brown ; on 5th and 

 6th segments a velvety-black ocellated spot, with a kidney-shaped 

 whitish spot within the black ; on the 6th, 7th, 8th, 9th and 1 Dth 

 segments an oblique lateral stripe of lilac and white, similar to those 

 in the larva of Sphinx ligustri, but shorter ; horn very short. As 

 to the cause of the dimorphism in the larvae of this species, Weismann 

 observes (Studies in the Theory of Descent, transl. pp. 296, 301) that the 

 larvae of E. elpenor, when young, rest on the leaves, but, when 

 adult, rest by day among the dead branches and leaves of its 

 food plant, Epilobium hirsutum, and on the ground among the tangled 

 leaves and branches if feeding on E. parvifolium. The change 

 thus appears to be associated with a change in habit, and it is 

 probable that this (and similarly coloured species with similar 

 habits) first acquired the habit of concealing itself by day on the 

 ground and among dead herbage, before the original green colour 

 could have been changed into brown by natural selection. The 

 adult larvae are, therefore, sometimes browm and sometimes green, 

 because the anciently-inherited green has not yet been completely 

 replaced by the newly-acquired brown coloration, some individuals 

 still retaining the old green colour. 



Development of larval markings. — First stadium : 4mm. in 

 length, of a yellowish-white opalescent colour (directly after hatching), 

 the large and somewhat curved caudal horn being black ; so 

 transparent that (under a low magnifying power) the nervous, 

 tracheal and alimentary systems could be beautifully seen. As 

 soon as the larvae began to feed they became green in consequence of 

 the food appearing through the skin, but the latter also gradually 

 acquired a dark green colour (pi. iv., fig. 17). All the specimens 

 (20) were exactly alike and showed no trace of marking. Second 

 stadium : The first ecdysis occurred after 5-6 days. Length of larvae 

 now 9mm.-iomm., shining green, the horn becoming a little red at the 

 base, while a fine white subdorsal line extended from the horn to 

 the head (fig. 18). The head and legs green ; the segmental 

 divisions appear as fine light rings, the entire upper surface of the 

 segments also crossed by line transverse rings (as also was the case 

 in the 1st stage). At the beginning of the present stage no trace 

 of the eye-spots could be detected, but a few days after it was 

 observed that the white subdorsal line was no longer straight on the 

 4th and 5th segments, but had curved upwards into two small 

 crescents. The latter soon stood out more strongly, owing to the 

 filling up of their concavities with darker green. These are the 

 first rudiments of the eye-spots (figs. 19 and 30). A very line white 



