6 4 



ANIMAL BIOLOGY 



The Abdomen. - -About how many segments or rings in 

 the abdomen ? Do all grasshoppers have the same num- 

 ber 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 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 breath- 

 ing 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 



FIG. 107. A GRASS- 

 HOPPER DISSECTED. 



