14 



STRUCTURE OF INSECTS. 



-n 



19. The skin of insects is in general very hard, and almost 

 horny ; it forms a kind of solid case, in the interior of which are 

 placed the muscles, viscera, 



&c. ; it fulfils the functions 

 of an external skeleton, and 

 is divided by a series of 

 rings more or less con- 

 siderable in number. 



20. The body is divided 

 into three perfectly distinct 

 parts ; namely, head, thorax, 

 and abdomen. 



21. The head (a, Jig. 3) 

 is not subdivided into 

 rings : it sustains the 

 mouth, and two little stems 

 or articulated horns, called 

 antenna, or feelers (c). 

 These little organs are 

 probably the seat of the 

 sense of touch ; their 

 length and form vary very 



, J J Fig. 3. ANATOMY OF AN INSECT. 



much ; sometimes they are 



filiform, at others like a saw, club-shaped, &c. 



The surface of the head is sometimes divided into regions; namely, the 

 clypeus (Latin, buckler), that part to which the labrum or upper lip is at- 

 tached ; the face, the front, the vertex or summit, and the cheeks. 



22. The thorax (d,f, i,Jig. 3), or middle portion of the body, 

 is sometimes called the corselet, although this name, strictly 

 speaking, belongs only to the second ring of the thorax, which, 

 in all insects, is composed of three rings or segments, each one 



Explanation of Fig. 3. Anatomy of the tegumentary system of a 

 winged insect (a grasshopper) : a, the head ; b, the eyes ; c, the an- 

 tennae ; d, the prothorax, or first ring of the thorax ; e, the first pair 

 of legs ; /, the mesothorax, or second ring of the thorax, bearing the first 

 pair of wings (g), and the second pair of legs (h) ; i, the metathorax, or 

 third ring of the thorax, bearing the second pair of wings (j}, and the third 

 pair of legs (k) ; I, the abdomen ; m, the femur or thigh ; n, the tibia or 

 leg ; o, the tarsus or foot. 



19. What purposes does the skin of insects fulfil? 



20. How is the body of insects divided ? 



21. Is the head divided into rings? What parts are attached to the 

 head? 



22. To what part of the thorax does the name corselet particularly be. 

 long ? Of how many pieces is the thorax composed ? To what parts are 

 the legs and wings of insects attached ? 



