20 



THE CLASS OF INSECTS. 



(tergal) and under (sternal) surfaces are most equally devel- 

 oped, while the pleura! line is reduced to a minimum. In the 

 thorax the pleural region is much more developed, either quite 

 as much, or often more than the upper, or tergal portion, while 

 the sternal is reduced to a minimum. In the head the pleurites 

 form the main bulk of the region, the sternites are reduced to 

 a minimum, and the tergites may be identified in the occiput, 

 the clypeus, and labrum. 



TABLE OF THE SEGMENTS or THE HEAD AND THEIR APPENDAGES, 



BEGINNING WITH THE MOST ANTERIOR.* 



PreoraL 



(Hypothetical), 

 First Segment 



(First Ocellary), 



Second Segment 

 (Second Ocellary), 



Third Segment 

 (Ophthalmic), 



Fourth Segment 

 (Antennary), 



Fifth Segment 

 (Mandibular), 



Sixth Segment 

 (First Maxillary), 



Seventh Segment 

 (Second Maxillary, or 

 Labial), 



The Appendages. We naturally begin with the thoracic 

 appendages, or legs,, of which there is a pair to each ring. The 

 leg (Fig. 25) consists of seven joints, the basal one, the coxa, in 

 the Hymenoptera, Lepidoptera, and Diptera, consisting of two 



* In the first column are enumerated the seven rings, or segments, composing 

 the head. The tergal parts (i.e. the labrum, epipharynx, and clypeus), situated in 

 front of the ocelli, are left out in enumerating the seven segments, as they are not 

 supposed by the author to belong to either of those segments. 



In the first column the seven rings are named (in brackets) according to the sort of 

 appendages they bear. In the second column is given the part, or parts, of the ideal 

 segment supposed actually to exist in an insect's head; and in the third column are to 

 be found the names of the organs attached to their corresponding segments, beginning 

 with the front and going back to the base of the head. 



