ENTOMOLOGY. 371 
food is always marked by a silken carpet. Soon after birth the caterpil- 
lars, huddled together as they are, form over the whole colony a silken roof 
with one cr more openings. These openings may be compared with the 
narrow gates leading to a fortified city. Of course as the caterpillars 
grow this tent is constantly enlarged, until it becomes large enough to 
attract the attention of the most careless gardeners. The caterpillars leave 
their nest twice every day, and leave it in good marching order. I do not 
mean to say that—like soldiers—they actually keep step, but at all events 
they leave by keeping in feeling with each other. Wherever the leader 
goes there all the others go as well. As they grow older and larger their 
excursions become more extensive, the food near by being eaten, notwith- 
standing all the efforts of the infested plants to repair damages. When 
the time arrives in which to shed their old and tov closely-fitting skins, 
an operation repeated four times, all the caterpillars retreat to their 
tent, under cover of which and protected by it against rain, the process 
of moulting takes place. At last the caterpillars have reached their full 
size, and the members of the colony, once so social in all their daily oper- 
ations, now scatter, and each caterpillar tries for itself to find a suitable 
place to transform into a pupa.. Soon a sheltered spot has been found. 
If born near fences the caterpillar will select the underside of the upper 
horizontal rail, and there spin a most delicate and beautiful cocoon. 
First fastening some loose silk to projecting parts to hold the more solid 
cocoon in position, this latter is formed in a most syemtrical shape and 
so transparent as to permit us to see very clearly all the operations of spin- 
ning going on in the inside. But soon the structure of the cocoon is filled 
with a sulphur-yellow powder, so that further observations become impos- 
sible. Inside this cocoon the pupal stage is reached, and a few weeks 
later the insect leaves it as a winged and sexual being. The form, mark- 
ings and colors of the different stages of both kinds of Tent caterpillars 
are given upon the illustration before you. There is but one annual 
brood. 
The difference between the two species is not great, yet constant. 
The Orchard Tent-caterpillar (Clisiocampa americana) is found abund- 
antly every spring. It is very partial to certain plants, prefering, besides 
the orchard trees, the wild cherry, plum, and haws found in Minnesota. 
Along the edges of our prairies the large tents of these caterpillars are a 
common feature during the first warm weeks of spring. 
The Forest Tent-caterpillar (Clisiocampa sylvatica), however, is more de- 
voted to the forest trees, though by no means disdaining fruit trees, and 
in years like the past one not a single kind of native trees is free from its 
attacks. Oaks, basswood, ash, maple, elm, boxelder, poplars and wil- 
lows, are all more or less infested, nor do the smaller bushes escape injury. 
In extreme cases even the different kinds of evergreens do not escape en- 
tirely. As already mentioned, this species does not spin such a con- 
spicuous nest or tent, otherwise the habits are almost identical. Nor does 
it always undergo its moults inside or below a tent; in many cases hund- 
reds of these caterpillars were closely huddled together for this purpose, 
upon the trunk of an oak not protected by any silken covering whatever. 
Yet close observation showed that all rested upon a carpet of silk, and 
whenever a caterpillar moved it would invariably leave a fine silken 
thread behind, so fine as to be barely visible even with a strong magnify- 
ing glass. 
