68 
LABORATORY EXERCISES 
their number and position? Their use? Note under the base of 
the wings, on the first abdominal segment, a pair of shiny oval 
membranes, the tympanums. What is their use? Draw the 
abdomen from the side. 
III. The Internal Structure. (This study is optional with the 
instructor.) Study a prepared dissection of a female locust from 
which the dorsal exoskeleton has been removed. (See Waggoner, 
Fig. 188.) 
1. All along the dorsal surface of the abdomen, just beneath the 
body wall, lies the delicate heart, a tube-like structure. 
2. The respiratory organs are a system of air tubes, the trachece, 
which ramify throughout the body. They are connected with the 
outside by their openings, the spiracles. The tracheae may be 
seen as glistening white threads and sacs in freshly killed speci¬ 
mens. (See Waggoner, Fig. 189.) 
3. A mass of yellow eggs will probably be found in the anterior 
part of the abdomen. This mass may be separated into right and 
left parts. From each a tube, the oviduct, leads to the ovipositor. 
4. After removing the reproductive organs, the digestive system 
may be studied. The mouth leads into a buccal cavity, which opens 
into the esophagus. This is followed by the large crop. In the 
crop the dark liquid is produced which the locust ejects from its 
mouth. The crop extends through most of the thorax. It leads 
into the fore-stomach. Next is the stomach proper. From the 
anterior end of the stomach arise the gastric cccca, double cone- 
shaped pouches. These lie parallel with the digestive tube. The 
stomach extends posteriorly through the fourth segment of the 
abdomen and leads into the intestine. This becomes smaller 
toward the posterior end and bends dorsally as it opens into the 
rectum. Make a drawing of the digestive system. 
5. The excretory system consists of a large number of fine, 
thread-like, whitish tubes that arise at the anterior end of the 
intestine. 
6. The nervous system is similar to that of the earthworm. If 
possible, locate the “ brain.” This is dorsal to the labrum on the 
