56 ARTHROPODS 



Are the second and third pairs of legs attached to the 

 thorax? How many segments in each? Notice the shape 

 of the coxa and the coxal cavity in the second and third 

 pairs of legs. Notice the position of the trochanter in the 

 third pair of legs. Do you see any advantage in having it 

 in this position? 



Count the joints of the tarsus in each of the three pairs 

 of legs. This characteristic is used in the classification of 

 beetles. 



Make a drawing of ^ht ventral side of the thorax (X4)- 



(3) Lift up tl- outer wings on the dorsal side and pull 

 them out at right angles to the body. These are the elytra. 

 Notice from what segment of the thorax they come. To 

 what in the butterfly and moth can they be compared? Do 

 you think they could be used in flying? Do you know of any 

 use to which they could be put? Do you find veins present? 

 Do you find a line of division between the mesothorax and 

 the metathorax? Look just under the elytra, above the 

 inner wing, for a degenerated appendage. What segment 

 of the thorax does it come from? What does it signify? 

 This appendage is shown more plainly in the water beetle 

 (Dyticus). 



Study the inner wings as they lie folded over the abdomen. 

 Can you make out the method of folding? 



Straighten out the inner wing of the left side, being care- 

 ful not to tear it while the tangle is being unrolled. Pin it 

 down and look carefully at the wings. How do they com- 

 pare in texture with the wings of other insects? Note the 

 veins. Can you find the same veins and the same areas 

 that are present in the wings of the grasshopper? Draw 

 inner wing (X4)- 



