T6 INSECTS. 



shorter palpi. Separate and draw. For what kind of 

 feeding is this mouth adapted ? 



II. The Thorax. Note the relative development of the 

 thoracic segments. Which is largest ? Observe the con- 

 tour of the surface of the thorax at the junction of the 

 legs and of the wings with the body. The cavities into 

 which the coxae are fitted are called the coxal cavities. 

 The coxal cavities of the fore legs are open behind; i.e., 

 not surrounded posteriorly by the thoracic wall. 



III. The Legs. Examine the legs. Flex and extend 

 them, and observe the action of the joints. Find in each, 

 leg coxa, trochanter, femur, tibia, and tarsus. How many 

 segments in the fore and middle tarsi ? How many in 

 the hind tarsi ? Which segment of the hind tarsi is 

 largest ? Observe that the two claws of each tarsus are 

 cleft to their bases, and appear as four claws. 



IV. The Wings. Lift the chitinous sheaths (wing 

 covers or elytra) which meet by smooth edges along the 

 median dorsal line, completely covering the posterior part 

 of the body. 



Extend them at right angles to the body, and examine 

 the wings. Observe how they lie folded. With forceps 

 seize a wing by its costal margin, and draw it forward. 

 Observe how it opens automatically when drawn forward. 

 Compare this method of folding with that already studied 

 in the grasshopper. 



V. The Abdomen. Study the abdomen. Compare 

 upper and lower surfaces. Count the segments. Com- 

 pare this abdomen in form and structure with that of the 

 Hymenoptera studied. Why has the beetle less need for 

 flexibility in this part than the bee ? 



Development. From July to October inclusive, the 

 eggs of the black blister beetle are laid in masses of more 

 than a hundred in shallow excavations in the soil. The 



