HYLOICUS PINASTRI. 285 



and streaked on the sides with brown, more or less dark ; mandibles 

 shining brown ; caudal horn black and slightly granulated. Thoracic 

 legs very pale straw-colour, and slightly tipped with brown. Prolegs 

 dull pinkish-yellow, with two grey patches on each. Escutcheon 

 dark shining brown, traversed by the fine dorsal and longitudinal 

 lines, which appear of a pale buff colour (Chaumette). Larva laevis, 

 glauca, linea laterali flava. Caput luteum. Collum luteo nigroque 

 varium. Segmenta iineis transversis 8 nigricantibus penultimo 

 cornuto ; ultimo punctis nigris, scabro. Cornu nigrum, scabrum, 

 apice bifidum (Linne, Sys. Nat., xiith ed., pp. 802-803). There is 

 a very detailed description of the larva from hatching to pupation (in 6 * 

 instars) by Hartig in Liebich's Allg. Forst-und J^ag.-J^ourn., vi., p. 177; 

 the larva is also mentioned by Ratzeburg, Forst-Insecten, ii., pp. 74 et seq. 



Variation of larva. — The adult stage of the larva of H. 

 pinastri-is very variable, as shown by the figures in various works. 

 The variations arise on the one hand from the struggle between the 

 green ground-colour and the reddish-brown extending from above, 

 and, on the other hand, from a more or less complete disappearance 

 of the associated longitudinal lines. The latter are sometimes 

 completely retained, this being the case in a caterpillar figured by 

 Hiibner (Larvae, Sphinges, iii., Legitimes C, b), where both the subdor- 

 sal and supraspiracular lines are continuous from segment 1 1 to seg- 

 ment 1, an instance which may, perhaps, be regarded as a reversion 

 to the primary form. It has long been known that, in the larva 

 of this species, the mixture of brown and fir-green, interspersed 

 with conspicuous light yellowish and white spots, causes the adult 

 larva to present a very perfect adaptation to its environment. 

 Roesel says : " After eating, the larva remains motionless, and is then 

 difficult to see because it is of the same colour as its food, since 

 its brown dorsal line has almost the colour of the pine-twigs, and 

 who is not familiar with the fact that, beneath the green needles, 

 there is also much yellow to be found." This adaptation to the 

 needles and twigs obviously explains why this larva, in the adult 

 condition, is so far removed from those of Sphinx, with which the 

 moths are so nearly related (Weismann). Thellusson states that 

 the larvae found at Woodbridge were most variable in colour, 

 some bright green, others, in their last two stadia, varying from 

 green to brown, whilst others again were quite purplish in hue. 

 Ratzeburg notes that, before pupation, the larva shrinks much and 

 often changes its colour most strikingly. 



Development of larval markings. — First instar: The larvae 

 are 6mm. in length on emergence, of a light yellow colour ; the 

 head shining black with a yellow clypeus ; the caudal horn, forked 

 at tip, is at first yellowish, but soon becomes black, no particular mark- 

 ing present, but a reddish stripe extends along the region of the dorsal 

 vessel, and the course of the spiracles is marked by an orange-red line 

 (Studies in Theory of Descent, pi. vi., fig. 53 a-b) ; as soon as 

 the young larva is filled with food it acquires a greenish streak. 

 The first moult occurs after 4 days. Second instar: Immediately 

 after the first moult there is still an absence of distinct markings, with 

 the exception of a greenish-white spiracular line ; in the course of 



* Buckler and Weismann both agree (see pp. 283-284 and 285-286) in giving 

 the larva of this species only 5 instars. 



