INSECT STUDY
CECROPIA, OR EMPEROR-MOTH
The larvæ of this, the largest of Canadian moths, may be found early in September, as they wander about in search of a suitable branch upon which to fasten their cocoons. If the pupils are not successful in finding the larvæ, the cocoons can be found after the leaves have fallen, because their size makes them conspicuous. The only difficulty in finding them is due to their being of the same colour as the withered leaves, so that they are easily mistaken for the latter.
The pupils should be directed to look carefully at what appears at first sight to be a withered leaf attached to a tree or shrub, and in this way many cocoons of various moths will be found.
Observe.—The large size—from three to four inches long; the greenish colour; the stumpy legs; movements, as walking, feeling, clinging; the rows of warts, and short, stiff spines on these; the feeding habits, biting or sucking; eggs of parasites, for frequently these are found on the larvæ.
Place the larva in a box covered with gauze, and observe the spinning and weaving of the cocoon.
From what part of the body is the silk obtained? With what organs are the threads placed in position? What part of the cocoon is made first and what part is made last? What time is required for making the cocoon? How is the cocoon fastened to the tree? What provision is made in the cocoon for warmth, for protection from birds, for shelter from rain?
Cut open a cocoon and examine the pupa, noting the mummy-like case on which can be seen the impressions of the wings developing within.
If the cocoon is kept in the vivarium in a cool place, so that the conditions may be as nearly as possible like the natural conditions, the adult moth will emerge about the first of May. In April the cocoon should be wetted occasionally, as it would be if exposed to rains; this ensures more perfect development of the insect.
Observe.—At what part of the cocoon the moth makes an opening; the slow spreading and strengthening of the wings; the size and coloration of the moth; the feathery feelers; the position of the wings and sucking mouth parts when at rest.
Require the pupils to make drawings of the cocoon, larva, and adult.
The promothea moth, whose cocoons are common on lilac bushes, may be studied in the same way as the emperor.
Reference.—Silcox and Stevenson: Modern Nature Study
DRAGON-FLY
The larvæ of this insect may be obtained in May or June by scraping leaves, weeds, and mud from the bottom of ponds and allowing the mud and water to settle in a pail or tub. The larvæ may be distinguished from other aquatic creatures by the long insect-like body, three pairs of legs, and the "mask"—a flap with pincers at the end. This mask can be turned under the head and body when not in use, or it can be projected in front of the larva for catching prey. At the rear end are three tubes, which fit together to form the breathing tube.
The pupils should observe the above features, and also the movements, seizing of prey, breathing, moulting, semi-resting or pupa stage, at the close of which the pupa climbs up a reed or stalk of grass and bursts the skin from which the adult emerges.
The pupils should put into the aquarium various kinds of insects and decide what foods are preferred by the larva and the adult.
Observe.—The size, length of body, movements in flight, lace-like wings, and insect-killing habits of the dragon-fly.
Should dragon-flies be protected? Give reasons. Are all dragon-flies of the same size, build, and colour? At what time of year are dragon-flies most numerous?
Reference.—Silcox and Stevenson: Modern Nature Study.
OTHER CONSPICUOUS INSECTS
The potato-beetle, giant water-bug, eastern swallow-tail butterfly, and promothea moth are insects suitable as types to be studied by the pupils of Form I. The giant water-bug is the large, broad, grayish-brown insect that is found on the sidewalks in May and June mornings. (For information on the eastern swallow-tail and promothea see Metamorphosis, in Butterfly and Moth Collections.)