BRANCH ARTHROPODS; CLASS INSECTA : THE INSECTS i?3 



should be removed and softened in warm water before the 

 mouth-parts are examined.) On either side of this 

 proboscis is a peculiar pointed process which rises from 

 the under side of the head. These processes are the 

 labial palpi and serve to protect the sucking proboscis. 

 The proboscis itself is composed of the two greatly modi- 

 fied maxillce. Instead of being short, jaw-like and com- 

 posed of several pieces as in the locust, in the butterfly 

 each maxilla is a slender, flexible half tube applied against 

 its mate on the opposite side in such a way as to form a 

 perfect tube long enough to reach into the nectaries of 

 flowers when in use and capable of being compactly coiled 

 up at other times. Cut across the proboscis and note the 

 canal in the centre. Try to separate the two maxillae 

 which compose it. 



Make a drawing of the frontal aspect of the head with 

 the eyes and appendages. 



Compare the thorax with that of the beetle and that of 

 the locust. The prothorax is a freely movable narrow 

 ring or collar. The mesothorax and metathorax are fused 

 to form a large convex mass, of which fully five-sixths is 

 mesothorax and only one-sixth metathorax. Try to dis- 

 tinguish the boundaries of the two segments. Note the 

 three pairs of legs; the differences in size among them, 

 and the differences between them and the legs of the 

 locust and water-beetle. In one of the legs determine 

 the coxa, trochantcr, femur, tibia and tar sal segments. 

 Note the differences between the wings of the butterfly 

 and those of the locust and beetle. Note that the wings 

 are membranous, but are covered with many fine scales 

 (fig. 42), as is, indeed, the whole body. Rub off some of 

 these scales on a glass slide and examine ; note shape, 

 little stem or pedicel of insertion, and longitudinal stria- 

 tions. Examine under microscope a bit of wing from which 

 some of the scales have been rubbed. How are the scales 



