38 NATURAL HISTOBY OF INSECTS. 



The posterior part of the head (that is, the part which is 

 next to the thorax) is called the occiput. The top of the head 

 (Fig. 116, c), is called the vertex or crown. Just above the 

 upper lip (Fig. 116, Ji)* is usually a more or less square piece 

 (Fig. 116, $), separated from the neighboring parts by a suture 

 or groove; this piece is termed the clypeus*, but in the Two- 

 winged Flies it is called the hyperstoma. That part of the face 

 which is between the clypeus and a line drawn from one 

 antenna to the other, is called the front, while the part of the 

 face which is between this and the vertex, is called the fore- 

 head. The cheeks are that portion of the side of the head 

 which is between the eyes and-the mouth (Fig. 116, /). 



~" THE THORAX AND ITS APPENDAGES. 



Next to the head is the thorax, which is composed of three 

 segments (Fig. 89). The first segment is called the prothorax', 

 to this part is attached the first or anterior pair of legs*; the 

 second segment of the thorax is called the mesothorax*, and to 

 it are attached the middle pair of legs and the first or upper 

 pair of wings, when they are present; the third or last segment 

 of the thorax is termed the metathorax* '; the last pair of legs 

 is attached to it, and also the second or posterior pair of 

 wings, when these members are present. 



The upper part of the thorax is sometimes called the notum, 

 while the under part has received the name of sternum. Each 

 of these is divided into three parts, the same as the 

 thorax; thus there is a pronotum and a proster- 

 wifrraf , a metanotum and a metasternum^ etc. The 

 different parts of the legs are well shown in the 

 accompanying cut (Fig. 117), where e represents 

 the thigh (femur); f, the shank (tibia); and ft, the 

 foot, (tarsus); the latter is five-jointed, and the last 

 joint is terminated by two claws (i). The part to 

 which the thigh is attached at its upper end is 

 called the coxa*\, and between them is sometimes 

 a small piece called the trochanter.*\ 



* See Fig. 89, f See Fig. 103. 



