THE ABDOMEN, WAX GLANDS, AND STING. 



79 



Fig. 38. — Section o£ 

 small piece of wall of 

 poison sac of sting. 



,,-Lum 



{AGID) as their ducts, but the epithelium of the tubes appears to be 



of a secretory nature also, and, if it is not, it is hard to see any reason 



for their great length. It also does not look 



probable that the two little end bodies could 



form all the poison that fills the comparatively 



enormous sac. 

 The walls of the poison sac (fig. 38) are lined 



by a thick coat of laminated chitin {Int) thrown 



into numerous high folds. In the neck i5art of 



the sac the folds are arranged very regularly in 



a transverse direction and form interrupted 



chitinous rings, holding the neck rigidly open. 



The epithelium {Epth) contains nuclei {Nu), 



but the cell boundaries are very slightly marked. 



There is a distinct basement membrane (BM) , 



forming a tunica propria externallj', but there 



are no muscle fibers of any sort present except 



a few which are inserted upon the sac from some of the surrounding 



organs and which apparently act as suspensoria. 



The poison found in the sac has an 

 acid reaction and is supposed to consist 

 princij)ally of formic acid. Hence its 

 gland is known as the acid gland {AGl) 

 of the sting. 



The other sting gland is a short, very 

 inconspicuous, and slightly convoluted 

 whitish tube (figs. 36, 37, 41, and 57, 

 BGl) opening directly into the base of 

 the bulb ventrad to the opening of the 

 poison sac. Its walls consist of a thick 

 epithelium of distinct cells (fig. 39, 

 Epth) lined with a thin chitinous in- 

 tima (Int) and surrounded by a distinct 

 basement membrane {BM), but, as in 

 the other gland, there are ho muscles 

 present. The secretion of this gland is 

 said to be alkaline and the gland is 

 therefore known as the alkaline gland 

 {BGl) of the sting. 



Experiments made by Carlet (1890) 

 show that it is only the mixture of the 

 products from the two poison glands 



that is fully effective in stinging properties. Carlet's experiments were 



made upon houseflies and blowflies. He shows (1) that flies stung by a 



bee die almost instantly, (2) flies artificially inoculated with the secre- 



^•Lum 



Lum 



riG. 39.- 



-Sections of alkaline gland 

 of sting. 



