COMPARISON OF DIFFERENT INSECTS 289 



Exercise 29. Make a drawing of the inner surface of the third thoracic leg. 



Exercise 30. Make a drawing of the outer surface of the third thoracic leg. 



Exercise 31. Examine the wings of the bee under the compound micro- 

 scope and make a drawing showing the fine hooks and groove by means of 

 which the wings are locked together during flight. Also notice the arrangement 

 of the veins. 



SECTION X. COMPARISON OF THE FLY WITH THE LOCUST AND BEE 



Material. Probably the best material for the study of the anatomy of the 

 Diptera is some of the large horse-flies, like Tabanus atratus, although these 

 may be hard to secure in sufficient numbers. If these cannot be secured, any 

 of the smaller, more abundant species will suffice. The material may be pre- 

 served in 75 per cent alcohol, or dried, the latter method probably being pref- 

 erable for a study of the external parts ; the specimens should, however, be 

 placed in a moist chamber at least twenty-four hours before they are wanted 

 for use. 



Exercise 32. Write out a careful comparative description of the external 

 anatomy of the fly, comparing it with the locust and the bee, and noting the 

 following points of structure : 



1 . The divisions of the body, the body covering, and the segmentation. 



2. The head and its appendages, with the exception of the mouth-parts. 



3. The thorax and thoracic appendages. 



4. The abdomen and its segmentation. 



Exercise 33. Make a drawing of the wing of a fly, comparing it with the text 

 figure. 



SECTION XI. COMPARISON OF A BEETLE WITH THE LOCUST 



AND THE BEE 



Material. Almost any of the larger beetles will serve for this work, although 

 the May-beetle will probably be the easiest to secure. These should be pre- 

 served in the alcohol-glycerin solution. 



Exercise 34. Write out a comparison of the beetle with the locust and bee, 

 noting : 



1. The nature of the body covering, the segmentation, and the divisions of 

 the body. 



2. The head, including the eyes and antennae. 



(If time permits, the mouth-parts of the beetle might profitably be dissected 

 and compared with those of the locust.) 



3. The thorax, including the wings and wing-covers, especially noting the 

 modification of the wing-covers. 



4. The abdomen, the number of segments, etc. 



Exercise 35. Make a drawing of the antennae, wings, and wing-covers of 

 the beetle. 



