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.
Fig. 108.—Grasshopper Laying Eggs. (Riley.)
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?