Now for the choice of the season. Larvæ are to be found all the year round. Early in the spring, as soon as the buds are bursting, some break out of the eggs recently laid by the moths that appear in February and March. Later on, during April and May, a host of both butterflies and moths are busy arranging for their broods. Then, throughout the whole of the summer, thousands of caterpillars of all sorts and sizes are to be met with everywhere. And finally, during the bleak winter months, you may amuse yourself by digging the hybernators out of their hiding places where they rest themselves till the spring sun again calls them out to refresh them with the young and tender leaves of a new year. Thus, unless you are merely intending to search out certain species you happen to require, there is not much difficulty in settling on the season.
The day selected should be dry, for your work lies among the herbage of banks, meadows, and woods, and nothing is more unpleasant than wading through a wet and dense vegetation, or beating down on yourself a shower of large drops from the branches of trees and shrubs.
Having reached the hunting ground, the first thing to do is to look out for signs of the presence of larvæ rather than for the larvæ themselves. Healthy vegetation with sound leaves must be passed by as untenanted; but the presence of partly eaten foliage immediately arouses suspicion.
A little experience will soon enable you to distinguish between the ravages of larvæ and of slugs, snails, wasps, &c. Some of the smaller larvæ certainly eat out clean holes like those cut by Hymenopterous insects, but as a rule they bite away at the edges, leaving the midrib and the larger veins standing out almost naked.
By looking well into the edges of the eaten leaves, it is easy to see whether the marauders have been recently at work. If they are dried up and discoloured, it is not of much use to search; but if still green and moist, you may feel almost sure that the hungry larvæ are not far off.
In this case you will carefully turn over the leaves to examine the under sides, and also the leaf stalks and branches or stems; but you must be prepared for all kinds of protective mimicry. Little green caterpillars will be seen lying on the midrib or
veins, so straight and so still that they are scarcely perceptible. Others are snugly tucked in a depression of a leaf with the same result. Then we must also be prepared for the artful little tricks of the larvæ of Geometræ ([p. 268]), by which they imitate stalks and twigs so closely that a sharp eye is necessary to discriminate between the two.
While thus searching we may meet with the cast skin of a caterpillar. This gives us fresh hopes, and so we continue our careful examination. At last, on grasping a leaf in order to turn it over for inspection, we feel something hairy or something soft and smooth. But lo! it is gone. It is one of those numerous caterpillars that feign death and drop to the ground on the slightest sign of danger. We search below for it, but the density of the vegetation renders this hopeless, and we are just about to start off in search of a more productive locality when we espy a quantity of the excrement of larvæ lying on a little bare patch of ground close by. This gives us a new idea. Here is another indication of the presence of the creatures we require, one that we can put into practice; and by-and-by we learn that in many cases this is really the surest sign of their whereabouts.
We look at these little pellets of excrement, and gain at once some idea of the size of the larvæ that produce them. Then we observe whether they are fresh and moist, or dry and stale. If the latter, it is not of much use to examine the leaves above; but if otherwise, there is little doubt of our meeting with larvæ, as the present position they occupy is so truly marked. The leaves just over them are carefully examined, either by turning them over as before described, or, if the height of the foliage admits of it, by placing our heads below and looking upward.
If we find that the larvæ are some of those that endeavour to escape by feigning death and allowing themselves to drop at the slightest disturbance, the net is always kept beneath the leaves we are touching in order to intercept them in their downward journey.