8 



SCHOOL ENTOMOLOGY 



and angles of the wings are also named. Fig. 5 shows 



a typical wing with the names 

 of the veins, margins and 

 angles. 



8. The Abdomen. The 

 abdomen of an insect consists 

 of several segments which 

 are generally more typically 

 ring-like than in the rest of 

 the body. At the tip of the 

 abdomen, and formed by 

 modifications of some of the 

 segments, is the egg-laying 

 organ, ovipositor, of the fe- 

 males and the external gener- 

 ative organs of the males. 

 These may be so retracted 

 within the body as to be not 

 prominent. With few excep- 

 tions, there are no other 

 appendages on the abdomen 

 of adult insects. 

 Along the sides of the segments of the thorax and 

 abdomen are small holes, called spiracles. They are the 

 external openings of the breathing tubes which will be 

 described in the discussion of the internal anatomy. 



In any part of an insect's body, where two plates or 

 segments come together and make a flexible union, the 

 union is called a joint. If the plates have grown firmly 

 together the line of union is a suture. 



9. The Body Wall. The body wall of insects is 

 hardened with a substance called chitin. This serves to 

 give it stability of form and protects the insect. This 



FIG. 5. Wings of Butterfly 

 Showing Veins and Margins. 



1, costal margin; 2, humeral angle; 

 3, apical angle or apex ; 4, outer 

 margin; 5, inner angle; 5a, anal 

 angle (hind wing) ; 6, inner margin ; 

 6a, anal margin (hind wing). C., costal 

 vein; Sc., sub-costal vein; R., radial 

 vein (and branches) ; M., median vein; 

 Cu., cubital vein; A., anal veins. 



