THE AI-DOMEN, WAX GLANDS, AND STING. 



79 



BM- 



Nu- 



Epthi- 



-Lum 



{AOID) as their duels, 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 tAvo 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 munerous high folds. In the neck i)art 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 {E pth) contains nuclei (A^'O^ 

 but the cell boundaries are very slightly marked. 

 There is a distinct basement membrane (BJI), fi,:. 38. — Section oi 

 forming a tunica propria externallv, but there ^^^^^ p'''^^'' °^ ^'^•^ ''^ 



^ , ,., ,, ' poison sac of sting. 



are no muscle fibers or any sort present except 



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



organs and which apparently act as suspensoria. 



The poison found in the sac has an 

 acid reaction and is supposed to consist 

 principally 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. 3G, 37, 41, and 57, 

 BGI) opening directl}' into the base of 

 the bulb ventracl to the opening of the 

 poison sac. Its walls consist of a thick 

 epithelium of distinct cells (fig. 39, 

 EptJi) lined wath a thin chitinous in- 

 tima {Int) and surrounded by a distinct 

 basement membrane (BJI), but, as in 

 the other gland, there are no 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 thesecre- 



BM 



Epth -^ 



Fig. .39. — Sections of alkaline Rlaud 

 of stinK. 



