EXTERNAL ANATOMY OF THE GRASSHOPPER 1 



1. Examine a large Grasshopper and note that the body, as previously 

 seen in the Crayfish, is completely enclosed in the chitinous exoskeleton. 

 Note further that the body is definitely divided into the head, the thorax, 

 to which the legs and wings are attached, and the abdomen with distinct 

 segmentation. Make an outline drawing from the left side to show the 

 general body plan. 



2. Examine the head and note the following structures : (a) the very 

 flexible, jointed antennae ; (6) the two large compound eyes ; (c) three 

 simple eyes (ocelli) on the front of the head in the region of the ' fore- 

 head ' ; (d) the clypeus forming a median portion of the exoskeleton in 

 the front of the head with (e) the upper Up (labrum) lying just ventral. 



3. Carefully remove the labrum and find, underneath, the chewing 

 (mandibulate) mouthparts as follows : (a) a pair of toothed mandibles ; 

 (b) a pair of maxillae to each of which (c) a maxillary palp is attached, 

 and finally (d) the lower lip (labium) divided in the midline and bearing 

 a labial palp on each side. Draw the head from the front, showing the 

 structures as observed under paragraphs 2 and 3. 



4. Examine the thorax and note the heavy exoskeleton, particularly 

 on the ventral surface. There are three thoracic segments designated as 

 the prothorax, mesothorax, and metathorax, each of which bears a 

 pair of legs and the last two, in addition, a pair of wings each. Note 

 that the articulation between the prothoracic and mesothoracic segments 

 permits movement, but that the mesothoracic and metathoracic segments 

 are rigidly joined. 



5. Examine the wings and note the difference in the character of the 

 two pairs. Remove one of the large metathoracic legs. Note the follow- 

 ing segments : (a) the coxa, attached to the body ; (b) the small tro- 

 chanter, attached to the distal end of the coxa ; (c) the large tapering 

 femur ; (d) the straight, rod-like tibia with two rows of spines towards 

 the distal end; (e) the five-jointed tarsus with a pair of very sharp 

 claws on the last segment between which is a fleshy pad (pulvillus). 

 Make outline drawings of the two wings and a metathoracic leg. 



6. Examine the abdomen. Identify the eleven segments of which it 

 is composed and note that most of them are so attached as to permit a 

 considerable freedom of movement. Note further that the exoskeleton 

 of the abdomen, as in the Crayfish, is typically divided into a dorsal por- 

 tion (tergum) and a ventral portion (sternum), except in the first and 

 the last abdominal segments, in which the sterna are lacking. Note the 

 fusion of the sterna in abdominal segments 9 and 10. Find a pair of 

 breathing pores (spiracles) on the mesothoracic and metathoracic seg- 

 ments and on the first eight abdominal segments. Note the tympanum 

 on each side of the first abdominal segment. 



i B. pp. 113-117. 

 295 



