78 THE A'NATOMY of THE HONEY BEE. 



for they are sometimes connected by a bridge behind the eighth 

 tergum. The oblong plate {Oh) and its stalk represent the ninth 

 sternum, and since it carries both the arm of the sheath {ShA) and 

 the palpus (Pip) it still maintains its original relationships to the 

 gonapophyses. The membranous lobe arising from between the 

 oblong plates and overlapping the bulb of the sting (figs. 36 and 37, 

 IXS) must belong to the median part of the ninth sternum. 



The tenth segment (fig. 41, X) consists of a short, thick tube having 

 the anus {An) at its tip. It takes no part in the formation of the 

 sting, but is entirely inclosed in the dorsal part of the sting chamber 

 beneath the seventh tergum. 



In the accessory plates of the bee's sting we have a most excellent 

 illustration of how the parts of a segment may become modified to 

 meet the requirements of a special function, and also an example 

 of how nature is ever reluctant to create any new organ, preferring 

 rather to make over some already existing structure into something 

 that will serve a new purpose. 



There are four glands connected with the sting, two of which 

 are known to secrete the poison, which is forced through the canal 

 between the sheath and the lancets and ejected into the wound made 

 by the latter. It is this poison that causes the pain and inflammation 

 in the wound from a bee's sting, which would never result from a 

 mere puncture. The other two glands have been described as " lubri- 

 cating glands," being supposed to secrete a liquid which keeps the 

 parts of the sting mechanism free from friction. They lie within 

 the body cavity, one on each side against the upper . edge of the 

 quadrate plate, where thej'^ are easily seen in an extracted sting, each 

 being a small oblong or ovate whitish cellular mass. Transverse 

 microtome sections through this region show that each of these 

 glands opens into a pouch of the membrane between the quadrate 

 plate and the spiracle-bearing plate of the eighth tergum. Each 

 gland cell communicates with this pouch by a delicate individual 

 duct. The secretion of the glands is thus poured upon the outer sur- 

 faces of the quadrate plates and might easily run down upon the 

 bases of the lancets and the arms of the sheath, but, for all that, the 

 notion that it is lubricative in function is probably entirely conjectural. 



The large, conspicuous poison sac (figs. 36, 37, 41, and 57, PsnSc) 

 that opens by a narrow neck into the anterior end of the bulb of the 

 sting is well known to everyone at all acquainted with bees. The 

 poison which it contains comes from the delicate branched thread 

 attached to its anterior end (fig. 57), a minute tube which, if traced 

 forward a short distance from the sac, will be seen to divide into two 

 branches, which are long and much coiled and convoluted, each ter- 

 minating finally in a small oval enlargement {ACfl). These terminal 

 swellings are generally regarded as the true glands and the tubes 



