IMPERFECT SOCIETIES OF INSECTS. 303 
his immediate followers succeed in the same line, the head of the second 
touching the tail of the first : then comes an equal series of pairs, next of 
threes, and so on as far as fifteen or twenty. The whole procession moves 
regularly on with an even pace, each file treading upon the steps of those 
that precede it. Ifthe leader, arriving at a particular point, pursues a 
different direction, all march to that point before they turn. Probably in 
this they are guided by some scent imparted to the tracks by those that 
pass over them. Sometimes the order of procession is different ; the 
leader, who moves singly, is followed by two, these are succeeded by 
three, then come four, and so on. When the leader,—who in nothing 
differs from the rest, and is probably the caterpillar nearest the entrance to 
the nest, followed, as I have described, —has proceeded to the distance of 
about two feet, more or less, he makes a halt ; during which those which 
remain come forth, take their places, the company forms into files, the 
march is resumed, and all follow as regularly as if they kept time to music. 
These larvae may be occasionally found at mid-day out of their nests, 
packed close one to another without making any movement; so that, 
although they occupy a space sufficiently ample, it is not easy to discover 
them. At other times, instead of being simply laid side by side, they are 
formed into singular masses, in which they are heaped one upon another, 
and, as it were, interwoven together. Thus, also, they are disposed in 
their nests. Sometimes their families divide into two bands, which never 
afterwards unite.1 
The processionary caterpillars of the fir (those of Cnethocampa pityo- 
campa), like the preceding, live ina common silken net placed at the extre- 
mities of its branches, on which they feed ; and when they leave one tree 
to proceed to another, they also move in procession, but with this striking 
difference, that they all range themselves in a single file, the head of each 
so exactly touching the tail of that before it as to form apparently one vast 
caterpillar of from fifteen to twenty feet long, and thus traversing by a 
continuous and occasionally slightly jerking motion, without ever breaking 
their line, the path they have chosen. What is singular is, that if the first 
caterpillar of the file be touched with the hand or a stick, it shrinks and is 
visibly agitated, as if it feared to be stung by an Jchneumon, and the last of 
the file, even if composed of six hundred, makes at the same instant, as 
well as every intermediate individual, the same movements, as if struck by 
an electric shock. — The individuals of another processionary caterpillar, 
the perfect insect of which Mr. Ewing had not been able to rear, he informs 
us march in circles, or rather ovals, and, when young, follow one another 
round and round for hours together !* 
T have nothing further of importance to communicate to you on imper- 
fect societies : in my next I shall begin the most interesting subject that 
Entomology offers ; a subject, to say the least, including as great a portion 
both of instruction and amusement as any branch of Natural History 
affords ;—I mean those perfect associations which have for their great 
object the multiplication of the species, and the education, if such a term 
may be here employed, of the young. ‘This is too fertile a theme to be 
Confined to a single letter, but must occupy several. 
: Tan, &c. 
1 Reaumur, ii. 180, 
2 De Villiers, Ann. Soc. Ent. de France, i. 201. 
3 Westwood in Trans, Ent. Soc, Lond, ii, proc, lv. 
