BRANCH ARTHROPODS ; CLASS INSECTS: THE INSECTS 165 



segment and with the mesothorax, while the prothorax 

 is freely movable, and is covered above by a strong shield. 

 The chitin armor of the whole body is specially heavy 

 and strong, affording a great protection to the insect. 



On the flattened head note the compound eyes and the 

 peculiarly-shaped nine -segmented antenna. Are there 

 any ocelli ? Dissect out the mouth-parts. The beetle's 

 mouth is fitted for biting, the mouth-parts being in general 

 character like those of the locust, with distinct flap-like 

 labnun, dentate mandibles, jaw-like maxillce with long, 

 slender, four-segmented palpi and lip-like labium with 

 three-segmented palpi. Make drawings of the antennae 

 and mouth-parts. 



Note the character of the thoracic segments. Ex- 

 amine the wings and legs. The fore wings are modified 

 into strong horny sheaths, or elytra, which completely 

 cover and protect the folded hind wings. The hind wings 

 are large and membranous. How are they folded ? Note 

 the adaptation of the middle and hind legs for swimming. 

 Determine the various segments of the legs, i.e. coxa, 

 trocJiantcr, fcmnr, tibia and tarsus. Note the long longi- 

 tudinal median keel on the ventral aspect of the thorax. 



The abdomen articulates with the metathorax by the 

 full width of the broad first abdominal segment. It is 

 composed of a series of segments without appendages, of 

 about equal length but decreasing in width from in front 

 backwards. Of how many segments does the abdomen 

 seem to be composed when viewed from the ventral 

 aspect ? From the dorsal ? 



Make a drawing of the ventral aspect of the whole 

 body. 



TECHNICAL NOTE. After examining the abdomen thus far, re- 

 move it from the rest of the body, and boil it in dilute potassium 

 hydrate (KOH) in a test-tube. This will soften and partially bleach 

 the body wall, 



