THE ABDOMEN, WAX GLANDS, AND STING. 73 



almost entirely concealed within the seventh. It is very narrow 

 below, but is expanded at the upper parts of its sides (VIIIS) , where 

 it is partly visible below the eighth tergum and behind the seventh 

 sternum. The dorsal part of the ninth segment is membranous except 

 for a small apodeme-bearing plate on each side hidden within the 

 eighth tergum. The ninth sternum, on the other hand, is a well- 

 developed semicircular band (IXS) forming the ventral and ventro- 

 lateral parts of the ninth segment. It bears on each side two con- 

 spicuous lobes — one a small, darkly chitinized, dorsal plate (IClsp) 

 carrying a large bunch of long hairs, the other a large, thin, ventral 

 plate {2Clsp). Between these four appendicular lobes is ordinarily a 

 deep cavity, which is the invaginated penis (fig. 56 E), but in 

 figure D this organ is shown partly evaginated (Pen). While the 

 penis is really an external organ, the details of its structure will be 

 described later in connection with the internal organs of reproduction. 

 The tenth segment is entirely lacking in segmental form. The anal 

 opening is situated in a transverse membrane beneath the eighth ter- 

 gum {VI I IT), and below it is a thin chitinous plate, which may 

 belong to the tenth segment. 



In many insects the modification of the terminal segments of the 

 males in cbnnection with the function of copulation is much greater 

 than in the bee. The ninth segment often forms a conspicuous 

 enlargement called the hypopygium, which is usually provided with 

 variously developed clasping organs in the form of appendicular 

 plates and hooks. 



The development of the external genital parts of the drone has been 

 described by both Michaelis (1900) and Zander (1900). A small 

 depression first appears on the under surface of the ninth segment of 

 the larva shortly after hatching. Soon two little processes grow 

 backward from the anterior wall of this pouch and divide each into 

 two. The part of the larval sternum in front of the pouch becomes 

 the ninth sternum of the adult, while the two processes on each side 

 form the upper and lower appendicular lobes (the valva externa and 

 the valva interna of Zander) . The penis at first consists of two little 

 processes which arise between the valvae internae, but is eventually 

 formed mostly from a deep invagination that grows forward between 

 them. These four processes arising on the ventral side of the ninth 

 segment of the male larva are certainly very suggestive of the similar 

 ones that are formed in the same way on the same segment of the 

 female and which develop into the second and third gonapophyses 

 of the sting. If they are the same morphologically we must homol- 

 ogize the two clasping lobes of the ninth sternum in the male with 

 the two gonapophyses of this segment in the female. Zander (1900) 

 argues against such a conclusion on the ground that the genital pouch 

 is situated near the anterior edge of the segment in the female and 



