LEPIDOPTERA. 253 
trees, and devour the leaves at the moment of their development. 
In the evening these caterpillars come out of their common nest, 
and form a sort of procession; hence their name Procession Moth. 
“‘T kept some for a little time in my house in the country,” says 
Réaumur. “I brought an oak branch which was covered with 
them into my study, where I could much better follow the order 
and regularity of their march than I could have done in the woods. 
I was very much amused and pleased at watching them for many 
days. I hung the branch on which I had brought them against 
one of my window shutters. When the leaves were dried up, 
when they had become too hard for the jaws of the caterpillars, 
they tried to go and seek better food elsewhere. One set himself 
in motion, a second followed at his tail, a third followed this one, 
and soon. ‘They began to defile and march up the shutter, but 
being so near to each other that the head of the second touched 
the tail of the first. The single file was throughout continuous ; 
it formed a perfect string of caterpillars of about two feet in length, 
after which the line was doubled. There two caterpillars marched 
abreast, but as near the one which preceded them as those who 
were marching in single file were to each other. After a few rows 
of our processionists who were two abreast, came the rows of three 
abreast ; after a few of these came those which were four abreast ; 
then there were those of five, others of six, others of seven, others 
of eight caterpillars. This troop, so well marshalled, was led 
by the first. Did it halt, all the others halted: did it again 
begin to march, all the others set themselves in motion, and fol- 
lowed it with the greatest precision. . . . That which went on in 
my study goes on every day in the woods where these caterpillars 
live. . . . When it is near sunset you may see coming out of any 
of their nests, by the opening which is at its top, which would 
hardly afford space for two to come out abreast, one caterpillar. 
As soon as it has emerged from the nest, it is followed by many 
others in single file; when it has got about two feet from the nest, 
it makes a pause, during which those who are still in the nest con- 
tinue to come out; they fall into their ranks, the battalion is 
formed ; at last the leader sets off marching again, and all the 
others follow him. That which goes on in this nest passes in all 
the neighbouring nests; all are evacuated at the same time.” 
