CHAPTER II

STUDIES OF INSECTS

_The effect of great numbers upon the structure and habits of animals. The use of keys in finding the names of animals._

1. FIELD STUDIES

_Materials._

1. _Boxes_ for carrying insects. 2. A _net_. This may be homemade, using mosquito netting or fish net and a stout wire. If it is to be used for a dragnet for water insects, the wire must be stout and the netting strong. Make the net twice as long as wide. 3. A _cyanide jar_ for killing insects. 4. A few _paper triangles_ for carrying butterflies. 5. A _notebook_.

_Note._--Your instructor will give directions for obtaining the material called for in 3, 4, and 5.

_Directions._

Look carefully and quietly in the various situations noted below. Do not be in a hurry. Weedy meadows or vacant lots and neglected roadsides are good places for your first trips. Note concerning each insect found: (a) its name or something by which to identify it, (b) where you found it, (c) what it was doing, (d) its probable food. Record these observations in your notebook. Make a special study of such insects as your instructor may designate.

Where to look for Various Insects

_Grasshoppers, locusts, katydids._ Look along roadsides, waste places, gardens, especially weedy ones, weedy lots, and grassy meadows and pastures.

_Crickets._ Under old boards, along the edges of board or stone walks, along fences.

_Beetles._ Same locations as for crickets, and also on flowering plants, under loose bark of trees and stumps, in rotten logs, etc. For _water beetles_ drag edges of ponds and streams.

_Dragon flies._ Along water-courses, ponds, and swamps. Drag ponds and ditches for larvæ.

_Bees._ On flowering plants, especially on large patches of wild asters, golden-rods, and thistles.

_Wasps._ Sandy stretches,--especially along the water,--among flowering plants, under the eaves and roofs of outbuildings. Nests may be found in these latter places.

_Butterflies and moths._ In fields where there are many flowering plants; look carefully on the leaves of plants for caterpillars, and for eggs. Also look very carefully on the under side of leaves, on twigs, and on the bark of trees for chrysalids of butterflies and cocoons of moths.

_Bugs._ In same locations as for bees and grasshoppers and water beetles. Also on fruit.

_Aphids._ On the fresh growing tops of plants.

_Tree hoppers._ On trees and shrubs. Hold your net on the under side of branches and shake the branch vigorously.

_Flies._ Around decaying substances, as garbage, fruit, etc.; on flowering plants.

_Ants._ Sandy waste places, decayed logs, along walks, often in kitchens.

_Note._--At night many kinds of insects fly around electric lights or into open windows, attracted by the light and may easily be collected.

Form for Field Trip Report

The notes taken on a field trip may be conveniently tabulated for permanent record in the form indicated below:--

FIELD TRIP REPORT

Date________ Time________ Locality________ Pupil's Name________ ---------------------------------------------------------------- Name of Insect | Where Found | What it was Doing | Probable Food ---------------+-------------+-------------------+-------------- | | | | | |

In case the name of the insect is not known to you, use a number and some designation as to color or other mark by which it may be known until you have leisure to look up its name by means of keys or books on insects.

Special Field Studies

The questions below may be used for a more careful field study of any insect.

1. Just where was the insect found?

2. Note carefully what the insects are doing before they are disturbed by your presence. What did the insects do when you disturbed them? If you think this related to securing safety, explain what leads you to think so.

3. What senses do you conclude are well developed? Reason for your conclusion.

4. Has the insect a home? If so, what is its character?

5. What is the color? What is the relation between the color of the insect and its surroundings?

6. Is the insect solitary in its habits or associated with others of the same species? If in association with others, note the numbers, and what they are doing.

7. What modes of locomotion do you observe in this insect? Which is the most common? If it flies or jumps, note the distance.

8. If you find the young, note whether they differ from the adult in general appearance, and if so, in what ways they differ. Do they differ in food?

9. What other insects do you find in the same habitat?

2. A STUDY OF GRASSHOPPERS (LOCUSTS)

_Insects adapted to Life in Grassy Meadows and Fields_

_Materials._

Both living and dead specimens of grasshoppers. Various stages of young grasshoppers either dead or living. Some mounted specimens with wings spread. The wings of grasshoppers mounted in pairs between two glass slides for use with microscope or hand lens. Mounted preparations of mouth parts and tracheæ.

_Definitions._

_Orthoptera_, straight-winged insects, order to which belong grasshoppers, locusts, katydids, crickets, cockroaches, etc.

_Vivarium_, a cage in which living animals are kept.

_Anterior_, toward the head of an animal.

_Posterior_, opposite to anterior.

_Dorsal_, the upper surface of an animal.

_Ventral_, opposite to dorsal.

_Regions_, principal divisions of the body of an animal.

_Head_, _thorax_, and _abdomen_, the three distinct regions into which the body of a grasshopper is divided.

_Somite_, a ring-like division of the body of an animal.

_Prothorax_, _mesothorax_, and _metathorax_, the three divisions or somites into which the thorax of any insect is divided. A pair of legs is borne on each division.

_Exoskeleton_, an external skeleton.

_Femur_, _tibia_, and _tarsus_, the three principal divisions of the leg corresponding to thigh, shank, and foot.

_Veins_, thread-like thickenings of the wings.

_Ocelli_, the single or simple eyes of an insect, composed of a single eye element.

_Compound eyes_, made up of many eye elements.

_Auditory sacs_, organs for hearing in many animals.

_Antennæ_, the feelers borne on the head.

_Labrum_, the upper lip.

_Labium_, the lower lip, formed by the growing together of the second maxillæ.

_Mandibles_, primary jaws situated under the labrum.

_Maxillæ_, secondary jaws just in front of the labium, each composed of three parts, a palp, a spoon, and a tooth.

_Palps_, the jointed finger-like structures used to handle food, one pair on the labium and one pair on the maxillæ.

_Spiracles_, openings into the trachea found along the sides of the abdomen and thorax.

_Tracheæ_, slender tubes used for breathing organs among insects. They carry the air direct to the tissues in all parts of the body.

_Ovipositors_, structures on the posterior end of the abdomen of a female, used to deposit eggs.

_Metamorphosis_, refers to the development of the young of animals when striking changes in structure occur in the course of their growth. Metamorphosis is called _complete_ when the young have no resemblance to the adults, and _incomplete_ when there is a resemblance to the adult. In complete metamorphosis the stages are _larva_, _pupa_, and _adult_. In incomplete metamorphosis the stages are _nymph_ and _adult_.

_Observations._

_The Body._

1. Show how the shape of the grasshopper's body is well adapted to its needs.

2. Which region of the body is the thickest? What seems to be the reason for this? Which regions are capable of movement?

_Locomotion._

3. What are the various kinds of locomotion a grasshopper can use? Which are used in the vivarium and which when free in the laboratory?

4. Which legs are used in jumping? How are these legs especially adapted to this, in length, structure and direction? Could a grasshopper jump if the third pair of legs were arranged like the other two pairs? Why?

5. How is the animal able to cling to grass stems and not slip down? What is the direction of the body in relation to the stem or grass blade?

6. What is the position of the wings when at rest? when in use? How do the hind wings fold? How are the principal veins of the wings arranged to permit or facilitate this folding?

7. Contrast the fore and hind wings with respect to thickness, size, and use.

8. To which somites of the thorax are the wings attached? Nearer which surface, the dorsal or ventral? Why?

_Sense Organs._

9. Discover all you can about the uses of the antennæ by carefully observing grasshoppers at rest, feeding, jumping and crawling, approaching an object or another grasshopper, etc.

10. How many compound eyes has the grasshopper? How many simple eyes? Where are they located?

Examine a preparation of the compound eye with the low power or as demonstrated with the stereopticon. What is the shape of an eye element of the compound eye? About how many eye elements are there in a compound eye?

_Feeding._

11. Do grasshoppers eat and drink while in captivity? Put a fresh bunch of grass which has been sprinkled with water in a vivarium with grasshoppers that have had no food or drink for twenty-four hours and watch results.

12. What is the position of the grasshoppers in feeding? In what direction do the jaws move in feeding? Compare this with the direction of movement of your own jaws. What is the use of the palps? What do you think is the use of the "molasses" or saliva that flows from the mouth?

_Respiration._

13. Describe the breathing movements of a grasshopper and explain the relation of the movements to inhalation and exhalation of air.

14. Find the exact location and number of spiracles on the abdomen. There are two pairs of spiracles on the thorax. Find them. How do the spiracles prevent the entrance of dust?

Describe a trachea as seen in a mounted preparation with the aid of a microscope or stereopticon.

_Protection._

15. Explain how the colors of the grasshopper may be protective or useful when at rest in its natural habitat and when in flight.

16. Does the shell cover the entire body? What are the advantages of such a covering? A shell is likely to hinder activity, sensitiveness, and growth. How are such disadvantages overcome in this case?

17. What senses are probably most relied upon to detect approaching danger? Give evidence to support your answer.

18. What is the position of the hind legs when at rest? What relation has this to safety?

_Reproduction and Development._

19. Describe the ovipositors and the probable method of their use. Describe the egg packets of grasshoppers, if discovered. About how many eggs in one? (They are sometimes seen against the glass sides of the vivaria.)

20. If you have young grasshoppers of various ages, arrange a set of them in what seems to you to be the order of their development. How do young grasshoppers differ from adults? What changes take place as they develop? What kind of metamorphosis is this?

Summary of Important Points in the Study of the Grasshopper

1. How many and what distinct regions of the body are there?

2. How many antennæ? Compare their length with that of the body. What other sense organs did you discover?

3. How many legs? For what specially adapted? How?

4. How many wings? What is their resting position? How do the fore wings differ from the hind wings? How do the hind wings fold?

5. To what kind of feeding are they adapted, biting or sucking the food? How many and what sets of mouth parts are there?

6. How is air necessary for respiration obtained?

7. In what various ways are grasshoppers fitted for life in meadows and weed plots?

8. How do they meet winter conditions?

9. What kind of metamorphosis has the grasshopper?

_Drawings suggested._

a. Side view with the legs and wings removed. Label all parts shown in this drawing. (See Definitions on pages 23 and 24 for names of parts.)

b. Face view of the head, showing the simple and compound eyes, the antennæ, labrum, and palps.

c. One of the third pair of legs. Label parts.

d. A fore and a hind wing arranged in natural position.

e. A young grasshopper.

3. COMPARATIVE STUDY OF ORTHOPTERA

_Materials._

Mounted specimens of various common species of orthoptera.

_Observations._

1. Where does the insect live? What is its color?

2. What is the size and shape as compared with the grasshopper?

3. What is the length of the antennæ as compared with the length of the body?

4. To what kind of locomotion are the legs adapted? How? Are the forelegs specially adapted for grasping?

5. What is the position of the wings when at rest? Are they large or small as compared with the size of the body?

6. Are the ovipositors long or short? (Compare with those of the grasshopper.)

7. Find the group to which the insect belongs and its name by the key in the following section.

4. KEY TO SOME COMMON ORTHOPTERA

A. Groups

============================================================================= LEGS |ANTENNÆ| OTHER CHARACTERS | GROUPS -----------------+-----------------------------------------+----------------- Similar, fitted | Long | Body flattened, wings folded on | Cockroaches for running | | dorsal surface of the abdomen | (_Blattidæ_) -----------------+-------+---------------------------------+----------------- First pair of | Rather| Prothorax long and slender, | Mantis legs enlarged | long | wings folded on dorsal | (_Mantidæ_) for grasping | | surface of abdomen | -----------------+-------+---------------------------------+----------------- Similar, fitted | | Body usually greatly elongated | Walking stick for walking | Long | and stick-like, usually no | (_Phasmidæ_) | | wings | -----------------+-------+---------------------------------+----------------- Hind legs fitted | | Body somewhat compressed, | Short-horned for jumping | Short | wings folded on side of | grasshoppers | | abdomen | (_Acrididæ_) |-------+---------------------------------+----------------- | | Body compressed, wings folded | Long-horned | Long | on sides, tarsus four-jointed | grasshoppers | | | (_Locustidæ_) |-------+---------------------------------+----------------- | | Body somewhat flattened, wings | Crickets | Long | folded on the back, tarsus | (_Gryllidæ_) | | three-jointed | =============================================================================

B. Species or Genera

============================================================================ CHARACTERS OF SPECIES | COMMON NAME | GROUPS -------------------------------------+----------------------+--------------- Large size, brown color | American cockroach | Small size, pale brown | "Croton bug" | Cockroaches Dark color, often wingless | Oriental cockroach | -------------------------------------+----------------------+--------------- Body long, anterior portion slender | Mantis or rear horse | Mantis -------------------------------------+----------------------+--------------- Long body, long legs, no wings | Walking stick | Walking sticks -------------------------------------+----------------------+--------------- Very large size, wings very small | Lubber grasshopper | Small to medium size, legs marked | Red-legged | with red | grasshopper | Short-horned Large size, greenish brown color | Differential locust | grasshoppers Medium to large size, sand color | Carolina locusts | (gray) | | -------------------------------------+----------------------+--------------- Rather large, green, wings large | Angle-wing katydid | and angled | | Long-horned Small to rather large, usually green | Meadow grasshopper | grasshoppers Wingless, brown color | Cricket grasshopper | -------------------------------------+----------------------+--------------- Usually rather large, black | Field cricket | Crickets Wingless, front legs shovel-shaped | Mole cricket | ============================================================================

5. THE DRAGON FLY

_An Insect adapted to Aerial Life_

_Materials._

Mounted specimens of dragon flies, some moist preserved specimens, living specimens if practicable, simple lenses.

_Observations._

1. Identify the three regions of the body and note the presence of a distinct neck. What is the length of the insect? What is its general form? If you have living specimens, discover what movements the head and abdomen are capable of making.

2. What is the position and general character of the wings? Explain how these wings are made very efficient for flying. Why should they not fold?

3. For what do the legs seem best adapted? Why?

4. Note the size of the eyes and of the antennæ? How do you account for the great size of the eyes and the relatively small antennæ?

5. What is the type of mouth parts, biting or sucking? If you have living dragon flies, try feeding them flies or mosquitoes and note how they are seized.

6. The food of dragon flies is mosquitoes and flies caught while on the wing. In what various ways is the dragon fly specialized for getting food in this manner?

_Summary._

How is the dragon fly fitted for its aerial life with respect to its body, means and method of locomotion, sense organs, kind of food and manner of obtaining it?

_Suggested drawing._

a. Dorsal view, showing veining of one wing.

6. THE HONEYBEE

_A Study of Adaptations for Community Life_

_Materials._

Preserved specimens of workers in small vials and in watch glasses, and some mounted specimens. A demonstration case showing the three kinds of members of the community, stages in the development of the workers and queens and the cells in which they are reared, specimens of the comb. Small pieces of beeswax, a box of honey, and specimens of comb free for examination. Mounted preparations of mouth parts and stings. Simple lenses and compound microscopes.

_Observations._

_The Worker Bee._

1. Observe and describe the form, size, regions, and covering of the bee. What are its colors?

2. Observe and describe the texture, veining, relative size, and position of the wings. Discover how the fore and hind wings are hooked together. What advantage in having them hooked together?

3. For what kind of locomotion are the legs best adapted?

4. Find the pollen basket on the tarsus of a hind leg. How is it fitted for carrying pollen? What are the wax shears?

a. Examine and describe the structure at the posterior end of the body used for stinging. (Use a mounted preparation for this with low-power of microscope.)

b. The mouth parts are fitted for both biting and sucking. Find what makes this possible. (Use mounted preparation.)

5. Describe the antennæ and the number, position, and shape of the eyes. Are the eyes fitted for keen sight? Give reason for answer.

6. The worker bee gathers honey and pollen and defends the entire community from enemies. What various adaptations fit it for this work?

_The Community of Bees._

7. How do the workers, drones, and queen differ in general appearance?

8. Describe the appearance of the comb and the arrangement and shape of the cells. Why this shape? How are the cells closed when full of honey?

9. How do the cells used for rearing worker bees differ from those used for rearing queens? What is the appearance of the larvæ? Of the pupa?

10. Examine and test in various ways a small piece of beeswax. What are the qualities possessed by this wax which make it suitable for making comb and protecting the home from storms?

Supplementary Studies of Bees

_Materials._

For this study an observation hive of bees or opportunity to visit an apiary will be helpful. If neither are practicable, then look up the answers in books. There are government bulletins on bee-keeping and much helpful information can be obtained from large dealers in bees and bee supplies.

_Observations._

1. How do bees protect their hives from rain and storm and light?

2. What are honey boxes? Where are they placed in the hive? Can the honey be removed late in the fall?

3. How is it safe to approach and handle bees in removing honey and caring for them?

4. What are their habits in entering and leaving the hive? What is the appearance of a returning loaded worker bee?

5. How do bees survive the winter? Why are the drones driven away or killed?

6. Watch bees gathering nectar and pollen from flowers and describe the process. Try following a bee on its journeys.

7. When the bees are in the hive, how may you know the queen and drones from the workers?

8. What is swarming? When does it take place? How is the swarm hived?

9. What is the home of wild honeybees? How found?

Summary of the Study of Honeybees

How is the work of the community of bees divided among the bees? How is each fitted for the work? What do you think of the success of this kind of life? Give reasons for your answer.

7. GENERAL STUDY OF INSECTS[1]

[1] This study is intended for an alternative study in case it is not practicable to use the studies of living insects. With slight adaptation it can be made useful for any insect, either preserved or living.

_Materials._

Both living and preserved specimens of the insects studied should be at hand, if practicable. There also should be specimens of the young.

_Observations._

_The Body._

1. What is the shape and size of the insect and the number of regions in its body? Does the shape seem to be in any way adapted to the mode of life of the insect? If so, how?

_Locomotion._

2. What methods of locomotion has the insect? Which is the most used?

3. What is the position of the wings when at rest? What is the texture (_e.g._ thick, smooth, leathery, shell-like, membranous) of the fore and hind wings?

4. For what kind of locomotion are the legs fitted? How?

_Sense Organs._

5. How many antennæ has the insect? What is their character as to shape and length? How many simple and compound eyes?

_Feeding._

6. What is the food of the insect? How are the mouth parts specially adapted to obtaining this food?

_Note._--The mouth parts of insects may be jaws for biting, or may form a tube for sucking, or a beak for piercing and sucking.

_Respiration._

7. Look for movements of the body indicating breathing, and describe what you find. Discover the location of the spiracles.

_Protection._

8. What are the enemies of this insect? (Among the most important enemies of insects are birds, certain other insects, and various small vertebrates such as frogs, snakes, lizards, turtles, etc.) How does the insect protect itself from these enemies?

9. Describe the shell with respect to thickness and flexibility. What is the character of the surface as to roughness or smoothness or covering of hairs or scales?

_Reproduction and Development._

_Note._--It may be necessary to get answers to these questions from books.

10. Where are the eggs deposited? What is the number of the eggs? How soon do they hatch?

11. What is the food of the larva or nymph? Are the food habits of the insects harmful to man? If so, how?

12. Describe the larva as to form, color, and appendages. Is it capable of locomotion?

13. Is the metamorphosis complete or incomplete? If complete, describe the pupa and tell where it may be found.

_Drawings._

There should be one drawing of the insect to show its general characteristics; usually a dorsal view is best. For other drawings ask your instructor.

8. A REVIEW OF INSECTS

_Directions._

The answers to questions in this study may be conveniently written in the form of a table. Construct this table by placing the topics at the left and the names of insects at the top. Allow ample space, about one half inch for the horizontal spaces and one and one half inches in width for the vertical columns. Use one or two insects from each of the principal orders, letting the table extend across two opposite pages.

_Topics._

1. What is the habitat?

2. What regions has the body?

3. How many antennæ? What is their form?

4. What kinds of eyes has the insect? How many of each kind?

5. How many legs?

6. For what kind of locomotion are the legs adapted? Which legs are thus used?

7. How many wings? Membranous or thickened?

8. What is the position of the wings when at rest?

9. If the fore wings are thickened, what is their texture,--leathery, smooth and sheath-like, partly membranous, covered with scales?

10. What kind of mouth parts,--jaws for biting, a beak for piercing, a tube for sucking, adapted for both sucking and biting?

11. By what means is respiration accomplished?

Summary of Important Points from the Table

1. What characters are common to all the insects described in the table?

2. What are the various types of wings? Why do they vary?

3. What are the various types of legs? How are they characterized?

4. What are the various types of mouth parts?

5. Show how the variations in insects are related to the habitat and mode of life of the insect.

9. KEY TO THE PRINCIPAL ORDERS OF INSECTS

A^1 Insects with _no_ wings. (See list below.)

A^2 Insects with wings B

B^1 With _two_ pairs of wings. (See Note 1 below.) C

B^2 With _one_ pair of wings Diptera

C^1 Both pairs of wings _alike_ in structure, either membranous or scaly D

C^2 Fore and hind wings _unlike_ in texture, fore wings fold over hind wings E

D^1 Both pairs of wings _membranous_, not covered with scales F

D^2 Both pairs of wings covered with _scales_; mouth parts tubular for sucking Lepidoptera

E^1 Fore wings very _smooth_, sheath or shell-like, meeting in a _straight line_ when folded; legs adapted for walking, running, or swimming; mouth parts for biting Coleoptera

E^2 Wings not as in E^1 I

F^1 Wings membranous, usually folded or partly folded; _few nerves_ G

F^2 Both pairs of membranous wings usually _outspread_, _many nerves_; mouth parts for biting H

G^1 Wings membranous, hooked together and partly folded, or outspread, _few nerves_ in the wings; mouth parts for _both biting and sucking_; regions of the body usually very distinct Hymenoptera

G^2 Wings membranous, usually folded, _few nerves_; _mouth parts_, a _beak_ for sucking and piercing Hemiptera

H^1 _Outspread membranous_ wings, nearly equal in size; _antennæ very short_ and inconspicuous Odonata

H^2 As in F^2, but _antennæ not short_; wings sometimes folded Neuroptera

H^3 Both pairs of wings membranous, folded above the back; fore wings much larger than hind wings; ovipositors long; mouth parts rudimentary Ephemerida

I^1 Fore wings folded over hind wings, _crossing_ at their tips, which are membranous, base of wings thickened, mouth parts a beak for piercing Hemiptera

I^2 _Fore wings leathery_, folding either at side of body or on the back; mouth parts for biting, legs often adapted for _jumping_ Orthoptera

_Note 1._--When wings are folded, it will be helpful to remember that thickened fore or cover wings always have membranous wings folded beneath them.

_Insects with no wings_ _Order_

a. Body long and slender, stick-like; legs for walking. Walking stick Orthoptera

b. Grasshopper-like. Cricket grasshopper Orthoptera