Beginners' zoology

The Grasshopper

Suggestions.—Collect grasshoppers, both young and full-grown, and keep alive in broad bottles or tumblers and feed on fresh grass or lettuce. When handling a live grasshopper, never hold it by its legs, as the joints are weak. To keep them for some time and observe their moults, place sod in the bottom of a box and cover the box with mosquito netting or wire gauze.

What is the general shape of its body? (Fig. 106.) Where is the body thickest? Is it bilaterally symmetrical, that is, are the two sides of the body alike? Is the skeleton, or hard part of the body, internal or external? Is the skeleton as stiff and thick as that of a crayfish? What is the length of your specimen? Its colour? Why does it have this coloration? In what ways does the grasshopper resemble the crayfish? Differ from it?

The Three Regions of the Body.—The body of the grasshopper is divided into three regions—the head, the thorax, and the abdomen. Which of these three divisions has no distinct subdivisions? The body of the grasshopper, like that of the earth worm, is made of ringlike segments. Are the segments most distinct in the head, the thorax, or the abdomen? Which region is longest? Shortest? Strongest? Why? Which region bears the chief sense organs? The appendages for taking food? The locomotory appendages? Which division of the body is most active in breathing?

The Abdomen.—About how many segments or rings in the abdomen? Do all grasshoppers have the same number of rings? (Answer for different species and different individuals of the same species.) The first segment and the last two are incomplete rings. Does the flexibility of the abdomen reside in the rings or in the joints between the rings? Is there merely a thin, soft line between the rings, or is there a fold of the covering? Does one ring slip into the ring before it or behind it when the abdomen is bent?

As the grasshopper breathes, does each ring enlarge and diminish in size? Each ring is divided into two parts by folds. Does the upper half-ring overlap the lower half-ring, or the reverse? With magnifying glass, find a small slit, called a spiracle, or breathing hole, on each side of each ring just above the side groove (Fig. 106). A tube leads from each spiracle. While the air is being taken in, do the two portions of the rings move farther apart? When they are brought together again, what must be the effect? In pumping the air, the abdomen may be said to work like a bellows. Bellows usually have folds to allow motion. Is the comparison correct?

How many times in a minute does the grasshopper take in air? If it is made to hop vigorously around the room and the breathing is again timed, is there any change?

Find the ears on the front wall of the first abdominal ring (Fig. 107). They may be seen by slightly pressing the abdomen so as to widen the chink between it and the thorax. The ears are merely glistening, transparent membranes, oval in form. A nerve leads from the inner surface of each membrane. State any advantage or disadvantage in having the ears located where they are.

Ovipositor.—If the specimen is a female, it has an egg-placer or ovipositor, consisting of four blunt projections at the end of the abdomen (Fig. 107). If it is a male, there are two appendages above the end of the abdomen, and smaller than the parts of the ovipositor. Females are larger and more abundant than males. In laying the eggs, the four blunt points are brought tightly together and then forced into the ground and opened (Fig. 108). By repeating this, the grasshopper makes a pit almost as deep as the abdomen is long. The eggs are laid in the bottom of the pit.

Draw a side view of the grasshopper.

Thorax.—This, the middle portion of the body, consists of three segments or rings (Fig. 107). Is the division between the rings most apparent above or below? Which two of the three rings are more closely united?

The front ring of the thorax is called prothorax. Is it larger above or below? Does it look more like a collar or a cape? (Fig. 106.) A spiracle is found on the second ring (mesothorax, or middle thorax) just above the second pair of legs. There is another in the soft skin between the prothorax and the mesothorax just under the large cape or collar. The last ring of the thorax is called the metathorax (rear thorax).

How many legs are attached to each ring of the thorax? Can a grasshopper walk? Run? Climb? Jump? Fly? Do any of the legs set forward? (See Fig. 106.) Outward? Backward? Can you give reasons for the position of each pair? (Suggestion: What is the use of each pair?) If an organ is modified so that it is suited to serve some particular purpose or function, it is said to be specialized. Are any of the legs specialized so that they serve for a purpose different from that of the other legs?

The leg of a grasshopper (as of all insects) is said to have five parts, all the small parts after the first four parts being counted as one part and called the foot. Are all the legs similar, that is, do the short and the long joints in all come in the same order? Numbered in order from the body, which joint of the leg is the largest,—the first, second, third, or fourth? Which joint is the shortest? The slenderest? Which joint has a number of sharp points or spines on it? Find by experiment whether these spines are of use in walking (Fig. 106). Jumping? Climbing? In what order are the legs used in walking? How many legs support the body at each step?

All animals that have ears have ways of communicating by sounds. Why would it be impossible for the grasshopper to have a voice, even if it had vocal cords in its throat? The male grasshoppers of many species make a chirping, or stridulation, by rubbing the wing against the leg. Look on the inner side (why not outer side?) of the largest joint of the hind leg for a row of small spines visible with the aid of a hand lens (Fig. 111). The sound is produced by the outer wings rubbing against the spines. Have you noticed whether the sound is produced while the insect is still or in motion? Why? The male grasshoppers of some species, instead of having spines, rub the under side of the front wing on the upper side of the hind wing.

Wings.—To what is the first pair of wings attached? The second pair? Why are the wings not attached to the prothorax? Why are the wings attached so near the dorsal line of the body? Why are the second and third rings of the thorax more solidly joined than the first and second rings?

Compare the first and second pairs of wings in shape, size, colour, thickness and use (Fig. 112). How are the second wings folded so as to go under the first wings? About how many folds in each?

Draw a hind wing opened out.

Head. What is the shape of the head viewed from the front, the side, and above? Make sketches. What can you say of the neck? Is the head movable in all directions?

What is the position of the large eyes? Like the eyes of the crayfish, they are compound, with many facets. But the grasshopper has also three simple eyes, situated one in the middle of the forehead and one just above each antenna. They are too small to be seen without a hand lens. How does the grasshopper’s range of vision compare with that of the crayfish?

Are the antennæ flexible? What is their shape? Position? Are they segmented? Touch an antenna, a wing, a leg, and the abdomen in succession. Which seems to be the most sensitive to touch? The antennæ are for feeling. In some species of insects they also are organs of hearing and smelling.

The mouth parts of a grasshopper should be compared with the mouth parts of a beetle shown in Fig. 113, since they correspond closely. If the grasshopper is fed with a blade of fresh grass, the function of each organ may be plainly seen. It is almost impossible to understand these functions by studying a dead specimen, but a fresh specimen is much better than a dry one.

The upper lip, or labrum, is seen in front. Is it tapering or expanded? In what direction is it movable? The dark pointed biting jaws (mandibles) are next. Are they curved or straight? Sharp or blunt pointed? Notched or smooth? Do they work up and down, or sideways? The holding jaws (maxillæ), each with two jaw fingers (maxillary palpi), are behind the chewing jaws. Why? The lower lip (labium) has a pair of lip fingers (labial palpi) upon it. The brown tongue, usually bathed in saliva, is seen in the lower part of the mouth. Since the grasshopper has no lips, or any way of producing suction, it must lap the dew in drinking. Does it merely break off bits of a grass blade, or does it chew?

The heart, circulation, nervous system, digestive and respiratory organs of the grasshopper agree mainly with the general description of the organs of insects given in the next section.

Microscopic Objects.—These may be bought ready mounted, or may be examined fresh. A portion of the covering of the large eye may be cut off and the dark layer on the inside of the covering scraped off to make it transparent. What is the shape of the facets? Can you make any estimate of their number? A portion of the transparent hind wing may be used, and the “veins” in it studied. A thin bit of an abdominal segment containing a spiracle will show the structure of these important organs.

Growth of the Grasshopper.—Some species hibernate in sheltered places and lay eggs in the spring, but adult species are scarce at that season. Most species lay the eggs in the fall; these withstand the cold and hatch out in the spring. Those hatched from one set of eggs sometimes stay together for a few days. They eat voraciously, and as they grow, the soft skin becomes hardened by the deposit of horny substance called chitin. This retards further growth until the insect moults, the skin first splitting above the prothorax. After hatching, there are five successive periods of growth. At which moult do the very short wings first appear? (Fig. 115.) After the last moult the animal is complete, and changes no more in size for the rest of its life. There has been an attempt among writers to restrict the term grasshopper to the long-winged, slender family, and to call the shorter winged, stouter family locusts, according to old English usage.

Economic Importance of Grasshoppers.—Great injury is often done to vegetation by grasshoppers; however, the millions of tiny but ravenous eaters hatched in early spring are usually soon thinned out by the birds. The migratory locusts constitute a plague when they appear, and they have done so since ancient times. The Rocky Mountain locusts flying eastward have darkened the sky, and where they settled to the earth ate almost every green thing. In 1874–5 they produced almost a famine in Kansas, Nebraska, and other Western states. The young hatched away from the mountains were not healthy, and died prematurely, and their devastations came to an end. Of course the migrations may occur again. Packard calculates that the farmers of the West lost $200,000,000 because of grasshopper ravages in 1874–5.

The cockroaches (Fig. 116), kindred of the grasshoppers, are household pests that have migrated almost everywhere that ships go. The praying mantis (Fig. 117), or devil’s horse, also belongs to this order. It is beneficial, since it destroys noxious insects. Which of its legs are specialized? The walking stick (Fig. 121) and the cricket (Fig. 118), like most members of the order, are vegetarian.

Are grasshoppers more common in fields and meadows, or in wooded places? How many different colours have you seen on grasshoppers? Which colours are most common?

Grasshoppers are very scarce in Europe as they love dry, warm countries. Why do locusts migrate? Give an instance in ancient times.

How long do most grasshoppers live? Does a grasshopper spread its wings before it flies? Does it jump and fly together? Can it select the place for alighting?

Note to Teacher.—Field work in Zoology should be systematic. Every trip has a definite region and definite line of study in view, but every animal seen should be noted. The habitat, adaptation by structure and habits to the environment, relations to other animals, classification of animals seen, should be some of the ideas guiding the study. The excursions may be divided somewhat as follows, according as opportunities offer: Upland woods, lowland woods, upland pastures, fields, swamps, a fresh-water lake, a pond, lower sea beach, higher sea beach, sand hills along shore, roadside, garden, haunts of birds, insect visits to flowers, ground insects, insects in logs.

Collecting Insects.—In cities and towns insects, varying with the season, are attracted by electric lights. Beetles and bugs will be found under the lights, moths on posts near the lights, grasshoppers and crickets and other insects in the grass near by. A lamp placed by a window brings many specimens. In the woods and in rocky places insects are found under logs and stones, and under the bark of dead trees. In open places, prairies, meadows, and old fields with grass and flowers, it will be easy to find grasshoppers, butterflies, and some beetles. Ponds and streams are usually rich in animal forms, such as bugs and beetles, which swim on or under the surface, and larvæ of dragon flies crawling on the bottom. Dragon flies and other insects that lay eggs on the water are found flying in the air above. (In the spring, newly hatched crayfish, tadpoles, and the eggs of frogs and toads should also be collected, if found.) Moths may be caught at night by daubing molasses or syrup made from brown sugar upon the trunks of several trees, and visiting the trees at intervals with a lantern.

An insect net for catching butterflies and for dredging ponds may be made by bending a stout wire into a circle one foot in diameter, leaving enough straight wire to fasten with staples on an old broomstick. To the frame is fastened a flour sack, or cone made of a piece of mosquito netting.

Butterflies and moths should be promptly killed, or they will beat their wings to pieces. The quickest method is by dropping several drops of gasoline upon the ventral (under) side of the thorax and abdomen. (Caution: Gasoline should never be used near an open fire, or lamp, as explosions and deaths result from the flame being led through the gasoline-saturated air to the vessel containing it.)

A cigar box and a bottle with a notched cork may be used for holding specimens. Cigar boxes may be used for holding collections of dried insects. Cork or ribbed packing paper may be fixed in the bottom for supporting the insect pins. Moth balls or tobacco may be placed in each box to keep out the insect pests which infest collections.

Captured insects which, in either the larval or the perfect stage, are injurious to vegetation, should always be killed after studying their actions and external features, even if the internal structure is not to be studied. Beneficial insects, such as ladybugs, ichneumon flies, bees, mantis (devil’s horse), dragon flies, etc., should be set free uninjured.

Anatomy and General Characteristics of the Class Insecta

The body of an insect is divided by means of two marked narrowings into three parts: the head, the chest, and the abdomen.

The head is a freely movable capsule bearing four pairs of appendages. Hence it is regarded as having been formed by the union of four rings, since the ancestor of the insects is believed to have consisted of similar rings, each ring bearing a pair of unspecialized legs.

The typical mouth parts of an insect (Fig. 123) named in order from above, are (1) an upper lip (labrum, ol), (2) a pair of biting jaws (mandibles, ok), (3) a pair of grasping jaws (maxillæ, A, B), and (4) a lower lip (labium, m, a, b). The grasping jaws bear two pairs of jointed jaw fingers (maxillary palpi, D, C), and the lower lip bears a pair of similar lip fingers (labial palpi, d). The biting jaws move sideways; they usually have several pointed notches which serve as teeth. Why should the grasping jaws be beneath the chewing jaws? Why is it better for the lower lip to have fingers than the upper lip? Why are the fingers (or palpi) jointed? (Watch a grasshopper or beetle eating.) Why does an insect need grasping jaws?

The chest, or thorax, consists of three rings (Fig. 124) called the front thorax (prothorax), middle thorax (mesothorax) and hind thorax (metathorax), or first, second, and third rings. The first ring bears the first pair of legs, the second ring bears the second pair of legs and the upper or front wings, and the third ring bears the third pair of legs and the under or hind wings.

The six feet of insects are characteristic of them, since no other adult animals have that number, the spider having eight, the crayfish and crabs having ten, the centipedes still more, while birds and beasts have less than six. Hence the insects are sometimes called the Six-Footed class (Hexapoda). The insects are the only animals that have the body in three divisions. Man, beasts, and birds have only two divisions (head and trunk). Worms are not divided.

Define the class insecta by the two facts characteristic of them (i.e. possessed by them alone), viz.: Insects are animals with ———— and ————. Why would it be ambiguous to include “hard outer skeleton” in this definition? To include “bilateral symmetry”? “Segmented body”? The definition of a class must include all the individuals of the class, and exclude all the animals that do not belong to the class.

The leg of an insect (Fig. 125) has five joints (two short joints, two long, and the foot). Named in order from above, they are (1) the hip (coxa), (2) thigh ring (trochanter), (3) thigh (femur), (4) the shin (tibia), (5) the foot, which has five parts. Which of the five joints of a wasp’s leg (Fig. 161) is thickest? Slenderest? Shortest? One joint (which?) of the foot (Fig. 161) is about as long as the other four joints of the foot combined. Is the relative length of the joints of the leg the same in grasshoppers, beetles, etc., as in the wasp (Figs.)? Figure 125 is a diagram of an insect’s leg cut lengthwise. The leg consists of thick-walled tubes (o, n) with their ends held together by thin, easy-wrinkling membranes which serve as joints. Thus motion is provided for at the expense of strength. When handling live insects they should never be held by the legs, as the legs come off very easily. Does the joint motion of insects most resemble the motion of hinge joints or ball-and-socket joints? Answer by tests of living insects. There are no muscles in the foot of an insect. The claw is moved by a muscle (m) in the thigh with which it is connected by the long tendon (z, s, t, v). In which part are the breathing muscles? As the wings are developed from folds of the dorsal skin, the wing has two layers, an upper and a lower layer. These inclose the so-called “nerves” or ribs of the wing, each of which consists of a blood tube inclosed in an air tube.

The abdomen in various species consists of from five to eleven overlapping rings with their fold-like joints between them. Does each ring overlap the ring in front or the one behind it?

The food tube (Fig. 127) begins at the mouth, which usually bears salivary glands (4, Fig. 127, which represents internal organs of the grasshopper). The food tube expands first into a croplike enlargement; next to this is an organ (6, Fig. 127), which resembles the gizzard in birds, as its inner wall is furnished with chitinous teeth (b, Fig. 114). These reduce the food fragments that were imperfectly broken up by the biting jaws before swallowing. Glands comparable to the liver of higher animals open into the food tube where the stomach joins the small intestine. At the junction of the small and the large intestine (9) are a number of fine tubes (8) which correspond to kidneys and empty their secretion into the large intestine.

The breathing organs of the insects are peculiar to them (see Fig. 128). They consist of tubes which are kept open by having in their walls continuous spirals of horny material called chitin. Most noticeable are the two large membranous tubes filled with air and situated on each side of the body. Do these tubes extend through the thorax? (Fig. 128.) The air reaches these two main tubes by a number of pairs of short windpipes, or tracheas, which begin at openings (spiracles). In which division are the spiracles most numerous? (Fig. 128.) Which division is without spiracles? Could an insect be drowned, i.e. smothered, by holding its body under water? Could it be drowned by immersing all of it but its head? The motion of the air through the breathing tubes is caused by a bellowslike motion of the abdomen. This is readily observed in grasshoppers, beetles, and wasps. As each ring slips into the ring in front of it, the abdomen is shortened, and the impure air, laden with carbon dioxide, is forced out. As the rings slip out, the abdomen is extended and the fresh air comes in, bringing oxygen.

The Circulation.—Near the dorsal surface of the abdomen (Fig. 131) extends the long, slender heart (Fig. 129). The heart has divisions separated by valvelike partitions. The blood comes into each of the heart compartments through a pair of openings. The heart contracts from the rear toward the front, driving the blood forward. The blood contains bodies corresponding to the white corpuscles of human blood, but lacks the red corpuscles and the red colour. The blood is sent even to the wings. The veins in the wings consist of horny tubes inclosing air tubes surrounded by blood spaces, and the purification of the blood takes place throughout the course of the circulation. Hence the imperfect circulation is no disadvantage. The perfect provision for supplying oxygen explains the remarkable activity of which insects are capable and their great strength, which, considering their size, is unequalled by any other animals.

The Nervous System.—The heart in backboned animals, e.g. man, is ventral and the chief nerve trunk is dorsal. As already stated, the heart of an insect is dorsal; its chief nerve chain, consisting of a double row of ganglia, is near the ventral surface (Fig. 131). All the ganglia are below the food tube except the first pair in the head, which are above the gullet. This pair may be said to correspond somewhat to the brain of backboned animals; the nerves from the eyes and the feelers lead to it. With social insects, as bees and ants, it is large and complex (Fig. 132). In a typical insect they are the largest ganglia.

The Senses.—The sense of smell of most insects is believed to be located in the feelers. The organ of hearing is variously located in different insects. Where is it in the grasshopper? The organs of sight are highly developed, and consist of two compound eyes on the side of the head and three simple eyes on the top or front of the head between the compound eyes. The simple eye has nerve cells, pigments, and a lens resembling the lens in the eyes of vertebrates (Fig. 134). The compound eye (Fig. 135) has thousands of facets, usually hexagonal, on its surface, the facets being the outer ends of cones which have their inner ends directed toward the centre of the eye. It is probable that the large, or compound, eyes of insects only serve to distinguish bright objects from dark objects. The simple eyes afford distinct images of objects within a few inches of the eye. In general, the sight of insects, contrary to what its complex sight organs would lead us to expect, is not at all keen. Yet an insect can fly through a forest without striking a twig or branch. Is it better for the eyes that are immovable in the head to be large or small? Which has comparatively larger eyes, an insect or a beast?

Inherited Habit, or Instinct.—Insects and other animals inherit from their parents their particular form of body and of organs which perform the different functions. For example, they inherit a nervous system with a structure similar to that of their parents, and hence with a tendency to repeat similar impulses and acts. Repeated acts constitute a habit, and an inherited habit is called an instinct. Moths, for example, are used to finding nectar in the night-blooming flowers, most of which are white. The habit of going to white flowers is transmitted in the structure of the nervous system; so we say that moths have an instinct to go to white objects; it is sometimes more obscurely expressed by saying they are attracted or drawn thereby.

Instincts are not Infallible.—They are trustworthy in only one narrow set of conditions. Now that man makes many fires and lights at night, the instinct just mentioned often causes the death of the moth. The instinct to provide for offspring is necessary to the perpetuation of all but the simplest animals. The dirt dauber, or mud wasp, because of inherited habit, or instinct, makes the cell of the right size, lays the egg, and provides food for offspring that the mother will never see. It seals stung and semiparalyzed spiders in the cell with the egg. If you try the experiment of removing the food before the cell is closed, the insect will bring more spiders; if they are removed again, a third supply will be brought; but if taken out the third time, the mud wasp will usually close the cell without food, and when the egg hatches the grub will starve.

The Development of Insects.—The growth and the moulting of the grasshopper from egg to adult has been studied. All insects do not develop exactly by this plan. Some hatch from the egg in a condition markedly different from the adult. The butterfly’s egg produces a wormlike caterpillar which has no resemblance to the butterfly. After it grows it forms an inclosing case in which it spends a quiet period of development and comes out a butterfly. This change from caterpillar to butterfly is called the metamorphosis. The life of an insect is divided into four stages: (1) egg, (2) larva, (3) pupa, and (4) imago, or perfect insect (Figs. 136, 137, 138).

The egg stage is one of development, no nourishment being absorbed. The larval stage is one of voracious feeding and rapid growth. In the pupa stage no food is taken and there is no growth in size, but rapid development takes place. In the perfect stage food is eaten, but no growth in size takes place. In this stage the eggs are produced. When there is very little resemblance between the larva and the imago, and no pupal stage, the metamorphosis, or change, is said to be complete. When, as with the grasshopper, no very marked change takes place between the larva and the imago, there being no pupal stage, the metamorphosis is said to be incomplete. By studying the illustrations and specimens, and by thinking of your past observations of insects, determine which of the insects in the following list have a complete metamorphosis: beetle, house fly, grasshopper, butterfly, cricket, wasp.

(All are wingless when young, and wingless adult forms occur in all the orders: order Aptera lacks wing-bearing thoracic structures.)

A single pair of wings is characteristic of the order Diptera.

A jointed beak, that is sheath-like, inclosing the other mouth parts, is characteristic of the order Hemiptera.

A coiled sucking proboscis and a wing covering of dust-like microscopic scales are characteristic of the order Lepidoptera.

Horny sheath-like fore wings, covering the hind wings and meeting in a straight line down the middle of the back, will distinguish the order Coleoptera.

Hind wings folded like a fan beneath the thickened and overlapping fore wings, will distinguish most members of the order Orthoptera.

The possession of a sting (in females) and of two pairs of thin membranous wings—the small hind wing hooked to the rear margin of the fore wing—will distinguish the common Hymenoptera.

Besides these, there remain a number of groups most of which have in the past been included under the order Neuroptera, among which the Mayflies will be readily recognized by the lack of mouth parts and by the possession of two or three long tails; the dragon flies by the two pairs of large wings, enormous eyes, and minute bristle-like antennæ; the scorpion flies, by the possession of a rigid beak, with the mouth parts at its tip; the caddis flies, by their hairy wings and lack of jaws; the lace wings, by the exquisite regularity of the series of cross veins about the margin of their wings, etc.

Exercise in the Use of the Table or Key.—Write the name of the order after each of the following names of insects:—

Moths and Butterflies.—Order ____? Why ____ (p. 82)?

The presence of scales on the wings is a never-failing test of a moth or a butterfly. The wings do not fold at all. They are so large and the legs so weak and delicate that the butterfly keeps its balance with difficulty when walking in the wind.

The maxillæ are developed to form the long sucking proboscis. How do they fit together to form a tube? (See Fig. 147.) The proboscis varies from a fraction of an inch in the “miller” to five inches in some tropical moths, which use it to extract nectar from long tubular flowers. When not in use, it is held coiled like a watch spring under the head (Fig. 148). The upper lip (labrum), under lip (labium), and lip fingers (labial palpi) are very small, and the mandibles small or wanting (Fig. 146).

The metamorphosis is complete, the contrast between the caterpillar or larva of the moth and the butterfly and the adult form being very great. The caterpillar has the three pairs of jointed legs typical of insects; these are found near the head (Fig. 141). It has also from three to five pairs of fleshy unjointed prolegs, one pair of which is always on the last segment. How many pairs of prolegs has the silkworm caterpillar? (Fig. 143.) The measuring worm, or looper? (Fig. 136.) The pupa has a thin shell. Can you see external signs of the antennæ, wings, and legs in this stage? (Fig. 143.) The pupa is concealed by protective coloration and is sometimes inclosed in a silken cocoon which was spun by the caterpillar before the last moult. Hairy caterpillars are uncomfortable for birds to eat. The naked and brightly marked ones (examples of warning coloration) often contain an acrid and distasteful fluid. The injuries from lepidoptera are done in the caterpillar stage. The codling moth (Fig. 141) destroys apples to the estimated value of $6,000,000 annually. The clothes moth (Fig. 171) is a household pest. The tent caterpillar denudes trees of their leaves. The only useful caterpillar is the silkworm (Fig. 143). In Italy and Japan many of the country dwellings have silk rooms where thousands of these caterpillars are fed and tended by women and children. Why is the cabbage butterfly so called? Why can it not eat cabbage? Why does sealing clothes in a paper bag prevent the ravages of the clothes moth?

Flight of Lepidoptera.—Which appears to use more exertion to keep afloat, a bird or a butterfly? Explain why. Of all flying insects which would more probably be found highest up mountains? How does the butterfly suddenly change direction of flight? Does it usually fly in a straight or a zigzag course? Advantage of this? Bright colours are protective, as lepidoptera are in greatest danger when at rest on flowers. Are the brightest colours on upper or under side of wings of butterfly? Why? (Think of the colours in a flower.) Why is it better for moths to hold their wings flat out when at rest? Where are moths during the day? How can you test whether the colour of the wings is given by the scales?

State how moths and butterflies differ in respect to: body, wings, feelers, habits.

Insects and Flowers.—Perhaps we are indebted to insects for the bright colours and sweet honey of flowers. Flowers need insects to carry their pollen to other flowers, as cross-fertilization produces the best seeds. The insects need the nectar of the flowers for food, and the bright colours and sweet odours are the advertisements of the flowers to attract insects. Flowers of brightest hues are the ones that receive the visits of insects. Moths, butterflies, and bees carry most pollen (see Beginners’ Botany, Chap. VI).

Comparative Study.—Make a table like this, occupying entire page of notebook, leaving no margins, and fill in accurately:—