116 INVERTEBRATE ZOOLOGY. 



higher power. The ocelli or simple eyes, one median, upon the ridg€> 

 between the antennae, and two lateral, at the inner, upper edge of 

 the compound eyes. The labrum, or upper lip, covering the mouth. 

 Lift this up and notice the two heavy black jaws, the mandibles. 

 These move laterally, and are toothed on the opposing inner sur- 

 faces. At the sides of the mandibles are four jointed tactile organs, 

 the palpi, attached to accessory mouth x^arts, not visible from 

 above. Look over the general surface for seams or sutm-es dividing 

 the head into separate areas. Of these the lateral pieces are the genae 

 or cheeks, the small median one just above the labrum is the clypeus, 

 and the remainder the epicraniuin. Make a large outline drawing of 

 the head from the front, putting in these details. 



2. Mouth parts. Turn the head over and separate the loose pieces about 



the mouth. The first (lowest) is a double piece with two palpi, then 

 will follow two lateral pieces, each resembling a half of the first 

 piece, and each with one palpus, and lastly the mandibles. These 

 pieces should be separately studied by placing them in a watch crys- 

 tal of 70 % alcohol, and using the dissecting lens. The separate lat- 

 eral pieces are the maxillae, and the double piece the labium or sec- 

 ond maxillae. Between them all is found a little fleshy projection, 

 the tongue. These parts, together with the labrum, constitute the 

 " mouth parts," the arrangement of which is as follows : 



labrKm. 

 Md. Md. 



Tongue. 

 Mx^. Mx^. 



Mx., + Mx.,. 



All of these, with the exception of the tongue, are believed to repre- 

 sent appendages. The labrum is plainlj^ a pair united in the middle, 

 and the notch in the center of the free margin of the lal)rum denotes 

 its double origin. Make a detailed drawing of the first maxilla and 

 the labiiim, noticing that each consists of a basal piece (two jointed) 

 two terminal plates, inner and outer, and a palpus. The palpi are 

 termed respectively, maxillary palpi and labial palpi . 



3. Segmentation of the head. As the fusion is complete, this is done en- 



tirely by counting the appendages, proving these, in doubtful cases, 



