50 THE ANATOMY OF THE HONEY BEE. 



the bee does not possess a hypopharynx. There is, however, a con- 

 spicuous chitinous plate located on the anterior part of the floor of the 

 pharynx (fig. 19, s) having two terminal points hanging downward 

 over the lower lip of the oral aperture, but, although this plate is truly 

 hypopharyngeal in position, it is not the homologue of the organ 

 called the hypopharynx in other insects. It is variously developed 

 in all Hymenoptera, being simply a chitinization of the floor of the 

 pharynx, and should be called the pharyngeal plate {Schlundbein of 

 Wolff). It will be more fully described in connection with the ali- 

 mentary canal. If a hypopharynx were present it should be situated 

 on the upper side of the labium (see fig. 3 D, Hphy) but there is here 

 present only a plain arched membranous surface in the honey bee 

 and other typical Hymenoptera. 



The external location of the salivary opening enables the saliva 

 to be mixed with the food before the latter enters the mouth. This 

 is necessary in insects since the jaws are also on the outside of the 



SaJDO 



\ Ls .. TMcl 



Lum 



"Mt 



Fig. 16. — Median section tlirougli distal half of mentum (Mt) and base of ligula (Lg) 

 of worlser, sliowing opening of salivary duct (SaWO), and muscles connected with 

 ligula and the "salivary syringe" (t). 



mouth, and whatever chewing or crushing the food receives from 

 them is consequently done in the preoral cavity. 



In some insects the saliva is used for other purposes than diges- 

 tion. For example, the saliva of some predaceous insects with pierc- 

 ing mouth parts belonging to the order Hemiptera is poisonous, and 

 when one of these insects " bites," the saliva is injected into the 

 wound by a special pump. The bite of the mosquito is made painful 

 likewise by an irritant secretion from a part of the salivary glands. 

 Bees appear to have the power of letting their saliva run down the 

 tongue when necessary to dissolve a hard substance like sugar and 

 render it capable of being taken up in solution, for they do not eat 

 sugar with their mandibles. Moreover, there is even a sort of pump 

 or so-called " salivary syringe " at the termination of the salivary 

 duct in the ligula, by means of which the secretion can be forcibly 

 ejected from the opening. 



The salivary opening on the base of the ligula (fig. 15 F, SaWO) 

 leads into a deep transverse pit with collapsible cartilage-like walls 

 having its deepest part turned horizontally toward the base of the 



