22 



CALIFORNIA STATE COMMISSION OF HORTICULTURE. 



THE ABDOMEN. 



This is the third and last portion of the 

 body, and is generally composed of nine seg- 

 ments. The number, however, varies greatly, 

 and in the cuckoo-flies there are but three or 

 four to be seen. The principal organs of the 

 abdomen are those of respiration, digestion, 

 and reproduction. The latter varies greatly 

 in different species, especially in the female, 

 in some cases being elongated into a long tube, 

 the ovipositor; in some being supplemented 

 with a sting; in others being supplied with 

 sawing or piercing organs; all of which serve 

 for the proper deposition of the egg in its 

 future food supply, which instinct forces the 

 mother insect to select. 



As stated above, the abdomen is composed 

 of nine segments, but these are not always 

 distinct. It is usually considered as com- 

 posed of two parts, the abdomen and post- 

 abdomen, the latter being composed of the 

 three terminal segments. In the abdomen 

 proper, we never find articulated appendages, with perhaps the single 

 exception of a small beetle, the Spiractha e^irymedusa. On the post- 



FIG. 23. Reprudiictive system 

 of queen honey-bee. a, acces- 

 sory sac of vagina; b, bulb of 

 stinging apparatus; c, coUe- 

 terial, or cement, gland; o, 

 ovary; od, oviduct; p, poison 

 glands; pr, poison reservoir; 

 r, receptaculum seminis; re. 

 rectum; i', vagina. (After 

 Leuckart.) 



FIG. 24. Diagrammatic cross-section of the thorax of an insect, a, alimentary 

 canal; d, dorsal vessel; g, ganglion; s, spiracle; lo, wing; 1, dorsal tracheal 

 branch; 2, visceral branch; 3, ventral branch. 



abdominal segments, such appendages are frequently found; as the 

 honey tubes of the aphids, the forceps of the earwigs, and the thick 

 bristles of the cockroaches. 



