their size. The dragon-fly's eggs are laid in the water; in some instances they are simply dropped and sink to the bottom; but in the case of damsel-flies, the mother punctures the stems of aquatic plants and places the eggs within them. The nymph in no wise resembles the parent dragon-fly. It is a dingy little creature, with six queer, spider-like legs and no wings; although there are four little wing-pads extending down its back, which encase the growing wings. It may remain hidden in the rubbish at the bottom of the pond or may cling. to water weeds at the sides, for different species have different habits. But in them all we find a most amazing lower lip. This is so large that it covers the lower part of the face like a mask, and when folded back reaches down between the front legs. It is in reality a grappling organ with hooks and spines for holding prey; it is hinged in such a manner that it can be thrust out far beyond the head to seize some insect, unsuspecting of danger. These nymphs move so slowly and look so much like their background, that they are always practically in ambush awaiting their victims.

Nymph of a damsel-fly.

Outdoor Studies, Needham.

The breathing of the dragon-fly nymphs is peculiar; there is an enlargement of the rear end of the alimentary canal, in the walls of which trachea or breathing tubes extend in all directions. The nymph draws water into this cavity and then expels it, thus bathing the trachea with the air mixed with water and purifying the air within them. Expelling the water so forcibly, propels the nymph ahead, so this act serves as a method of swimming as well as of breathing. Damsel-fly nymphs, on the other hand, have at the rear end of the body, three long, plate-like gills, each ramified with trachea.

Nymphs grow by shedding the skin. as fast as it becomes too small; and when finally ready to emerge, they crawl up on some object out of the water, and molt for the last time, and are thereafter swift creatures of the air.

References-American Insects, Kellogg. Comstock's Manual

Nymph of a dragon-fly.

Seen from the side, showing the position of the great lower lip when folded beneath the head.

From Outdoor Studies, Needha m.

LESSON LXXXV

THE DRAGON-FLIES AND DAMSEL-FLIES

Leading thought-The dragon-flies are among the swiftest of all winged creatures and their rapid, darting flight enables them to hawk their prey, which consists of other flying insects. Their first stages are passed in the bottoms of ponds where they feed voraciously on aquatic creatures. The dragon-flies are beneficial to us because, when very young and when full grown, they feed largely upon mosquitoes.

Method-The work of observing the habits of adult dragon-flies should be largely done in the field during late summer and early autumn. The points for observation should be given the pupils for summer vacation use, and the results placed in the field note-book.

The nymphs may be studied in the spring, when getting material for the aquarium. April and May are the best months for securing them. They are collected by using a dip-net, and are found in the bottoms of reedy ponds or along the edges of slow-flowing streams. These nymphs are so voracious that they cannot be trusted in the aquarium with other insects; each must be kept by itself. They may be fed by placing other water insects in the aquarium with them

or by giving them pieces of fresh meat. In the latter case, tie the meat to a thread so that it may be removed after a few hours, if not eaten, since it soon renders the water foul.

The dragon-fly aquarium should have sand at the bottom and some water weeds planted in it, and there should be some object in it which extends above the surface of the water which the nymphs, when ready to change to adults, can climb upon while they are shedding the last nymphal skin, and spreading their new wings.

Observations on the young of dragonflies-1. Where did you find these insects? Were they at the bottom of the pond or along the edges among the water weeds?

2. Are there any plume-like gills at the end of the body? If so, how many? Are these plate-like gills used for swimming? If there are three of these, which is the longer? Do you know whether the nymphs with these long gills develop into dragon or into damsel-flies?

Front view of the same nymph.
Outdoor Studies, Needham.

The same nymph seen from above.

Outdoor Studies, Needham.

3. If there are no plume-like gills at the end of the body, how do the insects move? Can they swim? What is the general color of the body? Explain how this color protects them from observation? What enemies does it protect them from?

4. Are the eyes large? Can you see the little wing-pads on the back

in which the wings are developing? Are the antennæ long?

5. Observe how the nymphs of both dragon and damsel-flies seize their prey. Describe the great lower lip when extended for prey. How does it look when folded up?

6. Can you see how a nymph without the plume-like gills breathes? Notice if the water is drawn into the rear end of the body and then expelled. Does this process help the insect in swimming?

7. When the dragon or damsel-fly nymph has reached its full growth, where does it go to change to the winged form? How does this change take place? Look on the rushes and reeds along the pond margin, and see

if you can find the empty nymph skins from which the adults emerged. Where is the opening in them?

Observations on the adult dragon-flies-1. Catch a dragon-fly, place it under a tumbler and see how it is fitted for life in the air. Which is the widest part of its body? Note the size of the eyes compared with the remainder of the head. Do they almost meet at the top of the head? How far do they extend down the sides of the head? Why does the dragon-fly need such large eyes? Why does a creature with such eyes not need long antennæ? Can you see the dragon-fly's antennæ? Look with a lens at the little, swollen triangle between the place where the two eyes join and the forehead; can you see the little, simple eyes? Can you see the mouth-parts?

2. Next to the head, which is the widest and strongest part of the body? Why does the thorax need to be so big and strong? Study the wings. How do the hind wings differ in shape from the front wings? How is the thin membrane of the wings made strong? Are the wings spotted or colored? If so, how? Can you see if the wings are folded along the front edges? Does this give strength to the part of the wing which cuts the air? Take a piece of writing paper and see how easily it bends; fold it two or three times like a fan and note how much stiffer it is. Is it this principle which strengthens the dragon-fly's wings? Why do these wings need to be strong?

3. Is the dragon-fly's abdomen as wide as the front part of the body? What help is it to the insect when flying to have such a long abdomen? Outline for field notes-Go to a pond or sluggish stream when the sun is shining, preferably at midday, and note as far as possible the following things:

I. Do you see dragon-flies darting over the pond? Describe their flight. They are hunting flies and mosquitoes and other insects on the wing; note how they do it. If the sky becomes cloudy, can you see the dragon-flies hunting? In looking over a pond where there are many dragon-flies darting about, do the larger species fly higher than the smaller ones?

2. Note the way the dragon-flies hold their wings when they are resting. Do they rest with their wings folded together over the abdomen or are they extended out at an angle to the abdomen? Do you know how this difference in attitude of resting determines one difference between the damsel-flies and the dragon-flies?

3. The damsel-flies are those which hold their wings folded above the back when resting. Are these as large and strong-bodied as the dragonflies? Are their bodies more brilliantly colored? How does the shape of the head and eyes differ from those of the dragon-flies? How many different colored damsel-flies can you find?

4. Do you see some dragon-flies dipping down in the water as they fly? If so, they are laying their eggs. Note if you find others clinging to reeds or other plants with the abdomen thrust below the surface of the If so, these are inserting their eggs into the stem of the plant. Supplementary reading-Outdoor Studies, Needham, p. 54; "The Dragon of Leunita" in Insect Stories, Kellogg.

water.

THE CADDIS-WORMS AND THE CADDIS-FLIES

P

Teacher's Story

EOPLE are to be pitied who have never tried to fathom the mysteries of the bottom of brook or pond. Just to lie flat, face downward, and watch for a time all that happens down there in that water world, is far more interesting than witnessing any play ever given at matinee. At first one sees nothing, since all the swiftmoving creatures have whisked out of sight, because they have learned to be shy of moving shadows; but soon the crayfish thrusts out his boxing gloves from some crevice, then a school of tiny minnows "stay their wavy bodies 'gainst the stream;" and then something strange happens! A bit of rubbish on the bottom of the brook walks off. Perhaps it is a dream, or we are under the enchantment of the water witches! But no, there goes another, and now a little bundle of sand and pebbles takes unto itself legs. These mysteries can only be solved with a dip-net and a pail half filled with water, in which we may carry home the treasure trove.

When we finally lodge our catch in the aquarium jar, our mysterious moving sticks and stones resolve themselves into little houses built in various fashions, and each containing one inmate. Some of the houses are made of sticks fastened together lengthwise; some are built like log cabins, crosswise; some consist simply of a hollow stem cut a convenient length; and some are

made of sand and pebbles, and one, the liveliest of all, is a little tube made of bits of rubbish and silk spun in a spiral, making a little cornucopia.

On the whole, the species which live in the log cabins are the most convenient to study. Whatever the shape of the case or house, it has a very tough lining of silk, which is smooth within, and forms the framework to which the sticks and stones are fastened. These little dwellings always have a front door and a back door. Out of the front door may protrude the dark-colored head followed by two dark segments and six perfectly active legs, the front pair being so much shorter than the other two pairs that

they look almost like mouth Log cabin caddis-worms in their cases feeding

upon a water plant.

Photo by J. T. Lloyd.

is thrust out and we see the hind segment of the thorax which is whitish, and behind this the abdomen of nine segments. At the sides

A caddis-fly.

of the abdomen, and apparently between the segments, are little tassels of short, white thread-like gills. These are filled with air, impure from contact with the blood, and which exchanges its impurities speedily for the oxygen from the air which is mixed with the water. Water is kept flowing in at the front door of the cabin, over the gills and out at the back door, by the rhythmic movement of the body of the little hermit, and thus a supply of oxygen is steadily maintained.

Photo by J. T. Lloyd.

The caddis-worm is not grown fast to its case as is the snail to its shell. If we hold down with forceps a case in which the occupant is wrong side up, after a few struggles to turn itself over, case and all, it will turn over within the case. It keeps its hold upon the case by two forward-curving hooks, one on each side of the tip of the rear segment. These hooks are inserted in the tough silk and hold fast. It also has on top of the first segment of the abdomen a tubercle, which may be extended at will; this helps to brace the larva in its stronghold, and also permits the water to flow freely around the insect. So the little hermit is entrenched in its cell at both ends. When the logcabin species wishes to swim, it pushes almost its entire body out of the case, thrusts back the head, spreads the legs wide apart, and then doubles up, thus moving through the water spasmodically, in a manner that reminds us of the crayfish's swimming except that the caddis-worm goes head first. This log cabin species can turn its case over dexterously by movements of its legs.

A caddis-worm removed from its case.

Showing gills and the hooks

on the last segment for holding fast to the

case.

The front legs of the caddis-worm are so much shorter than the other two pairs that they look like palpi, and their use is to hold close to the jaws bits of food, which are being eaten. The other legs are used for this too if the little legs cannot manage it; perhaps also these short front legs help hold the bits of building material in place while the web is woven to hold it there. The caddis-worm, like the true caterpillars, has the opening of the silk gland near the lower lip. The food of most caddis-worms

is vegetable, usually the various species of water plants; but there are some species which are carnivorous, like the net-builder, which is a fisher

man.

The caddis-worm case protects its inmate in two ways: First, from the sight of the enemy, and second, from its jaws. A fish comes along and sees a nice white worm and darts after it, only to find a bundle of unappetizing All of sticks where the worm was.

its

the hungry predatory creatures of the pond and stream would be glad to