20 



THE CLASS OF INSECTS. 



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

 oped, while the pleural line is reduced to a inininuiin. 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 i^leurites 

 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 of the Head 

 begixxixg with the most 



AND THEIR ApPEXDAGES, 

 AXTFUIOR.* 



{Hypothetical), 



Fu'st Segment 

 {First Ocellary), 



Second Segment 



{Second Ocellanj), 



Third Segment 



{Ophthalmic), 



rourtli Segment 



{Antennary), 



Fifth Segment 

 {Mandibular), 



Sixth Segment 

 {First Maxillary), 



Seventh Segment 

 {Second Maxillary, or 

 Labial), 



Preoral. 

 Tergal, 



\ Pleural, 



> Pleural, 



> Pleural, 



\ Pleural, 



Postoral. 



> Pleural, 



I Pleural, 



~i Tergal (occiput), 



> Pleural (gena), 

 J Sternal (gula), 



Labrnm, epipharynx. cly- 

 peus. 



Anterior ocellus (originallj- 

 double )- 



Two posterior ocelli. 



Eyes. 



Anteuuae. 



Mandibles. 



First maxillos. 



) Second maxillae 

 ) (Labium). 



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 ave 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, arc left out in enumerating the seven segments, as they are not 

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



In tlie first column tlie 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 actuaUy to exist in an insect's head ; and in the third column are to 

 bo found the n.ames of the organs attached to their corresponding segments, beginning 

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



