How To Study Living Animals


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 herunterladen.

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 herunterladen.

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 microsoft office kostenlos downloaden vollversion deutsch chip.

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.

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

2. 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?

3. 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?

4. 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?

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

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

Sense Organs.

1. 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.

2. 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.

1. 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.

2. 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.

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

2. 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.

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

2. 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?

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

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

Reproduction and Development.

1. 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.)

2. 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?