THE SENATORIAL DRYOCAMPA. 
405 
anterior extremity, ends behind with a long forked spine, 
and is surrounded, on each ring, with a notched ridge, the 
little teeth of which point towards the tail. Three of the 
grooves or incisions between the rings are very deep, thus 
allowing a great extent of motion to the joints, and these, 
with the notched ridges, and the long spine at the end of 
the body, enable the chrysalis to work its way upwards in 
the earth, above the surface of which it pushes the fore part 
of its body just before the moth makes its escape. 
Dryocampa^ oak or forest caterpillar, is a name originally 
applied by me to certain insects, found sometimes in great 
numbers on oak-trees, which then suffer very severely from 
their ravages. Of these caterpillars there are several kinds, 
resembling each other in shape, and in the form and situation 
of the thorns with which they are armed, but differing in 
color, and in the moths produced from them. They live 
together in swarms, but do not make webs; their bodies are 
cylindrical, remarkably hard and stiff, naked or not hairy, 
and have, on each ring, about six short thorns, or sharp 
points, besides two on the top of the second ring, which are 
long, slender, and threadlike, but not flexible, and project 
in the manner of horns. 
The most common of these 
Fig. 198. 
» 
caterpillars (Fig. 198) in 
Massachusetts is black, with ^ 
four narrow ochre-yellow stripes along the back, and two 
on each side. It is found in swarms of several hundreds 
together, on the limbs of the white and red oaks, during the 
month of August. The eggs from which they proceed are 
laid in large clusters on the under side of a leaf near the 
end of a. branch. The caterpillars are hatched towards the 
end of July, but sometimes earlier, and at other times later. 
At first they eat only the youngest leaves at the end of the 
branches and twigs, and, as they grow larger and stronger, 
proceed downwards, devouring every leaf, to the midrib and 
foot-stalk, from one end of the branch to the other. They 
