68 BRITISH LEPIDOPTERA. 



"Hist. Nat.," supp. in., p. 92., pi. viii., figs. a— b (1836); H.-Sch., "Sys. Bearb.," ii.,p. 

 106(1847); ? Bell.," Ann. Soc.Ent. Fr.," (3), viii., p. 688 (i860).— Alis ant. angusteflavo- 

 fasciatis, al. post. margine late flavo,saepiusbrunnescente(Staudinger, Cat., 3rd ed., p. 

 T2i). Larva: First stadium : To the naked eye the larva appears to be of a dark 

 chocolate colour,* slightly hairy, with a broad white mediodorsal band. The 

 structure and development of tubercles are as in the larvae of the other forms and races 

 ofZ. quercus. The lateral area is seen with the aid of a lens to be dull blue with 

 traces of the oblique stripes, the dorsal and subdorsal tubercles being yellow or orange 

 as in the other varieties, but the extent to which the yellow spreads from the bases 

 of the tubercles is greatly curtailed by the white dorsal band (this is the chief 

 cause of the difference in appearance from the English forms), and the black 

 margin or border on the subdorsal side of the yellow triangles is very greatly 

 developed, and still further curtails the yellow area which is the predominant 

 feature of the larvae of the French forms var. viburni and var. meridionalis. The 

 general effect on the larva of var. sicula, of the restriction of the yellow by black and 

 white areas, aided by the black or dark brown hairs, is to produce the dark 

 chocolate ground colour of the larva ; although, if a lens be used, or the larva be 

 placed in bright sunlight, the different colours which go to make up this general 

 effect can be clearly distinguished. The head of the larva of var. sicula is shiny 

 black with a trifoliate white marking on the face, being, possibly, a further f develop- 

 ment of the marking seen on the face of the larvae of var. viburni and var. 

 ■meridionalis (October 24th, 1 899). Second stadium (well-grown): The larvae do 

 not seem to differ greatly from those of var. viburni and var. meridionalis. Still 

 there is a superficial difference, due to the size of the markings, although the latter 

 appear to be fundamentally the same§. The lateral hairs are white and curve 

 downwards ; the dorsal hairs brown or black, and mostly short on thoracic seg- 

 ments; these short dorsal thoracic || hairs are very numerous, and form the 

 commencement of the coat which, in later stages, covers the dorsal area of all 

 the segments^ (Bacot, November 7th, 1897). Almost fullgrown (? Penultimate 

 instar). — 50mm. long when at rest, 58mm. when stretched, 7mm. wide at the 3rd 

 abdominal segment ; the head comparatively small, partially retractile within pro- 

 thorax, the width pretty uniform, but the meso- and metathorax rather less 

 than the prothorax and abdominal segments, of which the 3rd — 6th are rather 



* The larvae of var. meridionalis and var. viburni. in 1st stadium, are light 

 red- or orange-yellow, with white mediodorsal band ; but those of English L. 

 quercus and of var. callunae appear as dark blue-black laivae with orange 

 triangles on each segment, and the width and flatness of the triangles 

 almost suggest yellow transverse bands. The French races appear to be rather 

 more hairy ; the colour pattern is really the same, but the British races do not 

 develop the white mediodorsal band until about the 3rd stadium, and then only 

 as a chain of spots. The great difference in the appearance of the larvae, to the 

 naked eye (other than that caused by the absence or presence of the white band), 

 is brought about by the greater or less development of the yellow and black 

 areas (Bacot). 



t I am of opinion that the larva of var. sicula is the most specialised form 

 presented by the larvae of L. quercih and its numerous varieties with which I am 

 acquainted (Bacot). 



§ More distinctly marked in the larva of var. sicula than in the larva? 01 

 the other varieties is the resemblance that the markings, formed by the junction 

 of the lateral band with the transverse central dorsal stripe, bear to those of 

 Trichiura crataegi and Lachneis lanestris, in which the interrupted lateral (or 

 subdorsal) band and its junction with the divided transverse dorsal band form the 

 most noticeable feature of the larval markings (Bacot). 



|| The thoracic segments of the larger Lachneid larvae arc of special import- 

 ance when the larvae are young, compared with the abdominal. These segments 

 are usually larger in size, and bear specially bright-coloured markings, hairs, or 

 hair-tufts. Adult characters, too, are first developed on the thoracic segments, 

 e.g., Eutricha quercifolia, Cosmotriche potatoria, Odonestis pruni, Dendrolimus 

 pint and Macrothylacia rubi (Bacot). 



t This suggests that the thoracic segments ol~ the ancestral form had some 

 special development, from which have been evolved, on the one hand, the dorsal fur 



of the larva of L. quercus, and, on the other hand, the hair-tufts of the larva ol 

 Cosmotriche potatoria, as well as the special startling colours and scale-like hairs of 

 Dendrolimus pint and Eutricha querci folia (Bacot). 



