INTRODUCTIOK 9 



attachment by the four posterior pro-legs, at a very considerable angle 

 to the twig on which it rests. This strange attitude, in association 

 with special colouring and configuration, is eminently protective, render- 

 ing the caterpillar almost indistinguishable from the twigs it frequents. 

 Many taterpillars of Noctua3, having in addition to two pairs of pro- 

 legs possessed by the Geometers only one pair (on the ninth segment), 

 approximate the latter in their mode of progression, and are commonly 

 known as " half-loopers." 



While nearly all lepidopterous larvse are solitary, or only found in 

 close proximity owing to their having been hatched more or less re- 

 cently from a cluster of eggs, there are a few among those of moths 

 which are distinctly social, constructing a common silken nest in which 

 they remain until eventually assuming the chrysalis state. The most re- 

 markable of these social larvse are those of the so-called " Processionary " 

 Bombycid moths, which not only live in community, but, when they leave 

 the nest, proceed in long columns widening from the single leader to 

 many abreast, and return, after feeding, in the same regular order.^ 



On its first disclosure by the moult of the last skin of the cater- 

 pillar, the lepidopterous Puim or chrysalis exhibits a soft moist sur- 

 face, usually of a greenish or yellowish tint, the viscid secretion upon 

 which gradually hardens into a rather thin, but hard and firm, outer 

 casing or horny shell, closely investing the entire body, and binding 

 flatly upon the breast and sides the incipient trunk (Jiaustellum'), 

 antennae, palpi, legs, and wings. It is very remarkable that in the 

 chrysalis, from the very first, these various limbs are all distinctly 

 present in outline, or in mould as it were, and are to a great extent 

 free from the body at first, though subsequently the investing secretion 

 glues them down. 



Pupae, leading an absolutely quiescent life and requiring no food, 

 present but little variation in comparison to the larvas. In form, be- 

 sides being more elongate and slender in some groups than in others, 

 the only marked difference is presented by the chrysalides of most 

 butterflies, in which the head and thorax are more or less sharply 

 angulated. The surface in some is very smooth, but in most more or 

 less granulated or pitted. Many of the angulated butterfly chrysalides 

 bear on the back of the abdomen two rows of tubercles, usually more 

 or less pointed, and in a few cases prolonged into spinous processes. 

 Some of the Bombycid pupas (Liparidce), and also that of a South- 

 African Lycffinid butterfly (D' JJrhania), have dense tufts of hair. 



The colours of pupae are considerably varied in the case of those 

 fully exposed to the light or in very thin cocoons, but limited to various 



^ A characteristic " Processionary " inhabits the eastern part of Cape Colony and Natal ; 

 it is the Anaphe Panda of Boisduval. 



Westwood long ago described a Mexican Pieride butterfly (EucJicira soeialis), the larvse 

 of which " construct a very strong parchment-like bag, in which they not only reside, but 

 undergo their change to the pupa state ; " but he has not recorded, I believe, whether these 

 caterpillars are processionary. 



