THE BEETLE 55 



(2) Examine the ventral side of the head. Beginning 

 with the lower surface find the labial palpi and the tongue, 

 or glossa, situated in the central depression of the large, hard, 

 mentuin. On either side of the tongue find a pair of fleshy 

 paraglossae, generally lighter in color than the mentum. 

 Insert the scalpel in front of the paraglossae, loosen the 

 labium, and with the tweezers carefully inserted, grasp it 

 firmly and remove the parts studied. Lay them aside for 

 further study. On either side of the mentum find the bases 

 of the antennae. Notice their attachment to the head. Re- 

 move them and place them in proper relation by the side 

 of the labrum. 



The mouth parts next exposed are the maxillae. Remove 

 them and look carefully for the three parts ; the lacinia, galea, 

 and palpus. Place them above the other parts. Remove 

 next the mandibles and labrum and place them in proper 

 position in front of the others. Draw all the mouth parts 



(X4). 



Below the mentum is the enlarged gula divided into two 

 parts by a line. How does it compare with that of a grass- 

 hopper ? ■" 



The Thorax. — (i) Observe the prothorax on both 

 dorsal and ventral sides. Note its shape in front and back, 

 its margins, and its size compared with the prothorax of 

 other insects studied. On the ventral side observe the first 

 pair of legs. Where are they attached? Are all the seg- 

 ments common to the legs present? Do you find the coxal 

 cavity ? * 



(2) Do you find the mesothorax and the metathorax 

 on the ventral side? Ti'ace the boundaries of the thorax 

 and see if you find any peculiarities not common to insects. 



