INSECTS 



be retracted into the flexible membrane of the neck at 

 its base. 



One other structure ot interest in the cicada's head 

 should be observed. This is a force pump connected 

 with the duct (Fig. 122, SalD) of the large salivary glands 

 {Gl, Gl) and used probably tor injecting into the wound 

 of the plant a secretion which perhaps softens the tissues 

 of the latter as the bristles are inserted. Possibly the 



saliva has also a 

 digestive action 

 on the food liquid. 

 The salivary 

 pump (SalPmp) 

 lies behind the 

 mouth, and its 

 duct opens on the 

 extreme tip of the 

 tongue, where the 

 saliva c a n b e 

 driven into the 

 channel of the 

 second bristles. 

 Most sucking in- 

 sects have two 

 parallel channels 

 between these 

 bristles (Fig. 90), 

 one for taking 

 food, the other 

 for ejecting saliva, 

 and the cicada 

 probably has two 

 also, though in- 

 vestigators differ 

 as to whether 

 there are two or 

 only one. 



MdB 

 MxB' 



Fig. 122. Median section of the head and beak of 



an adult cicada 

 The sucking pump (Pmp) is the mouth cavity, the 

 collapsed roof of which (e) can be lifted like a piston 

 by the large muscles (PmpMcls) arising on the 

 clypeus (C/p). The liquid food ascends through a 

 channel between the maxillary bristles (MxB), is 

 drawn into the mouth opening (A/M), and pumped 

 back into the pharynx {Pky)> from which it goes into 

 the oesophagus (OE). A salivary pump (Sa/Pmp) 

 opens at the tip of the hypopharynx (Hphy) y dis- 

 charging the secretion of the large glands (G/, Gl) 



into the beak 



2O4 



