The young of the dragon-fly live a groveling existence, as different as can be from that of their sun-loving parents. Their food consists of mosquito larvæ, water-fleas and the like, and their method of catching their prey is as novel as it is effective. Pupils and teacher can get plenty of good healthy entertainment out of the behavior of these awkward and voracious little mask-wearers. The first dip of the net usually brings up a supply of dragon-fly nymphs and of their more slender cousins, the damsel-fly nymphs. The latter have expanded plate-like appendages at the hind end of the body which distinguish them from the dragon-fly nymphs.
Fig. 75. The life history of a dragon-fly as seen in an aquarium.
The transformation of one of these young insects into an adult is one of the most interesting observation lessons that can be imagined for a warm spring morning. If a dragon-fly nymph should signify its intention of changing its form in my school-room, I should certainly suspend all ordinary work and attend to him alone. Each child should see if possible this wonderful transfiguration.
Floating in the water of a pond or stream one may find a little bundle of grass or weed stems, with perhaps a tiny pebble clinging to the mass. Close examination will prove this to be the "house-boat" of one of our insect neighbors, the caddice-worm. Contrasting strangely with the untidy exterior is the neat interior, with its lining of delicate silk, so smooth that the soft-bodied creature which lives inside is safe from injury. The commonest of the many forms of houses found here are those illustrated in [Figs. 76] and [77]. These will find all they wish to eat in a well-stocked aquarium. When full grown they will leave the water as winged creatures, like [Fig. 78], and return to its depths no more.
Fig. 76. Case of caddice-worm
Fig. 77. Another caddice-worm case.
