How To Study Living Animals


THE DAMSEL FLY LARVA
Materials.

Living larvæ of the damsel fly in shallow watch glasses of water for individual use, and others in large pans or aquaria herunterladen. Simple lenses or dissecting microscopes.

Observations.

1. What is the color and the shape of the larva? how long is it? Notice in what surroundings in the water the larva lives, and answer to yourself how its form and color would protect it in those surroundings herunterladen.

2. Since the larva is an insect, though immature, its body is composed of three regions: head, thorax, and abdomen. How do these regions differ from each other microsoft office kostenlos downloaden vollversion deutsch chip?

3. What structures has your specimen to enable it to move from place to place? If fully developed wings are not present, what indication is there of their being formed?

4. What sense organs has the larva? Which ones seem to be the largest and most useful?

5. Although the aquatic larva is preparing for adult life in the air, there should be some arrangement for securing air in the water. Where do you find outgrowths of the skin which might increase the air-absorbing surface? How many of these structures are there? Look within them for the air tubes,—fine branching black lines.

6. If possible, without injury to the specimen, examine the larva’s mouth. Try to discover how it is used and how it is protected when not in use.

Suggested drawings.

a. The entire larva, × 4.

b. A gill, as seen through the microscope.

c. The feeding apparatus, × 10.