24 THE ANATOMY OF THE HONEY BEE. 



hei'e, as will Ix' shown in the s])ccial dcscriiitioii of the wing- of the 

 bee. 



Tlie abdomen consists almost always of 10 segments. There are 

 never any more than this number well developed in adult insects, and 

 if there are fewer the reduction is due to a modification of the ter- 

 minal segments to accommodate the external organs of reproduction. 

 The posterior oj^ening of the alimentary canal is at the end of the 

 tenth segment, which carries also two small appendages at the sides of 

 the anus. These are called the cei'ci (fig. 8, Cei-) . In some insects they 

 are short, styletlike processes, in others they are long and many 

 jointed, while in many they are absent. The cerci are supposed to 

 be developed from the embryonic appendages of the tenth segment, 

 although, on the other segments, these appendages disappear before 

 the embryo hatches, except in some members of the lowest wingless 

 order of insects, which have a pair of cercuslike appendages on each 

 segment of the abdomen. 



Each abdominal segment presents a tergum above and a sternum 

 below ; the former usually also reaches far down on the sides and 

 overlaps the edges of the sternum. In some insects one or more small 

 pleural plates intervene between the tergum and the sternum, but 

 the abdominal pleura are never developed in any way suggestive of 

 a thoracic pleurum. Very frequently there is present an upper 

 pleural plate, or epipleurite^ adjoining the edge of the tergum and a 

 lower, or hypopleurite^ adjoining the edge of the sternum. The line 

 sej^arating these two sclerites, however, is horizontal and can not 

 correspond with the vertical suture of a thoracic pleurum between the 

 episternum and the epimerum extending from the base of the leg 

 to the base of the wing. 



The most complicated structures on the abdomen are the external 

 organs of reproduction. In the male these serve as clasping organs 

 and take on a great variety of forms in different species. The organs 

 in the female form an ovipositor and are of much more definite and 

 constant structure. 



The ovipositor (fig. 8), in its most perfect development, consists of 

 three pairs of long, closely appressed bladelike processes called 

 gonapophyses {IG, 2G, 3G). These six pieces fit neatly together and 

 form an organ by means of which the female makes a hole in the 

 ground or in the bark of a tree, or punctures some other insect, and 

 then places her eggs in the cavity thus produced. An interesting fact 

 in this connection is that the sting of a wasp or bee is simply a modi- 

 fied ovipositor. This can be proved by a comparison of the organs 

 themselves or by a study of their development. Each is formed from 

 six little peglike processes that grow out from the sterna of the eighth 

 and ninth abdominal segments of the larva or young soon after hatch- 



