PHYSIOLOGY OF THE INVERTEBRATA. 45 



former secrete the silk-like material in wHicli the larvse invest 

 themselves on turning into the pupal state. 



(10) Tlhe Neuroptera. — In this order the mouth parts are 

 masticatory, although sometimes also suctorial. The alimen- 

 tary canal is somewhat similar to that of the Lepidoptera. 

 There are eight free Malpighian tubules. 



(11) The Hymenoptcra is the order to which bees, wasp3, 

 and ants belong. The mouth parts are for biting (ants), and 

 licking (bees). The labial palps are long and slender ; " there 

 are two large paraglossge, and between them a median, annu- 

 lated, setose, cylindrical organ proceeds, which either repre- 

 sents the lingua, or is an independent prolongation of the 

 ligula. Functionally this organ is a to7igue, and enables the 

 lee to lap tip tlu honey on %ohich it feeds. The mandibles and 

 raaxillEe are employed as cutting and modelling instruments, 

 bat appear to have little or nothing to do with mastication, 

 properly so called." 



In the bee the mouth opens into a slender oesophagus, 

 which extends the whole length of the thorax, and at whose 

 posterior end it dilates into the large honey-bag (Fig. 8). 

 Before any honey passes into the stomach the so-called 

 valve (i)* must be withdrawn by a special action. The 

 " valve " then returns to its usual position, and thereby 

 converts the crop (6) into a special receptacle for collecting 

 nectar until the bee reaches its hive. In the crop the nectar or 

 honey undergoes a change which prevents it(to a certain extent) 

 undergoing acetic fermentation. When the bee reaches its 

 hive the honey is regurgitated into waxen cells. The stomach 

 or chylific ventriculus (c) is very long and leads into a short 

 intestine (e), and then into a wide, distensible rectum {g). 



The poison of the Hymenoptera is a fluid containing formic 

 acid (HjOOj), which is secreted by a gland and retained in a 

 receptacle connected with the sting. The sting is nothing 

 more than a modified ovipositor.f In the larval bee the 



* Vide, next chapter. 



t See Lacaze-Duthiers's Bedhercliei sur I'armure (jiiitale fenuUe des 

 Insectes. 



