THE EP I PHARYNX 43 



writers (Kowalevsky, Carriere, and also Chatin) to represent a pair 



of appendages, but Heymons (LSI),")) refutes this view, stating as his 



reason that the labrum arises between the 



two halves of the nervous system (protocere- 



brum), while all the true appendages arise on 



each side of the nervous system. (See also 



Fig. 34.) 



In th'e fleas (Siphonaptera) both the clypeus 

 and labrum are wanting. 



While it apparently forms an anterior 

 specialized portion of the procephalic lobes, 

 Viallanes regarded it as belonging to the 

 third, or his tritocerebral, segment, since the nium; ftdyi""*; , abrum; 



o, o, ocelli ; e, eye ; <;, antenna ; 



labral nerves arise from the tritocerebral *. mandible ; mas portion of 



maxilla uncovered by the la- 



ganolia. But since in all the early as well brum; , maxillary palpus ;#', 



labial palpus. 



as late stages of embryonic life it appears 



to be situated in front of the mouth, it would seem to belong 



to the first segment. 



In the embryo of Blatta it first appears as a thick crescentic fold 

 being slightly divided anterior to the mouth, and in Doryphora it 

 appears as a heart-shaped or deeply bilobed prominence situated in 

 front of the mouth (Wheeler). 



The epipharynx and labrum-epipharynx. - - The epipharynx is the 

 under surface or pharyngeal lining of the clypeus and labrum, form- 

 ing the membranous roof of the mouth. As it contains the organs of 

 taste and has been generally overlooked by entomologists, we may 

 dwell at some length on its structure in different orders. 



Reaumur was, so far as we have been able to ascertain, the first 

 author to describe and figure the epipharynx, which he observed in 

 the honey bee and bumble bee, and called la langue, remarking that it 

 closes the opening into the oesophagus, and that it is applied against 

 the palate. According to Kirby and Spence, De Geer described the 

 epipharynx of the wasp; and Latreille referred to it, calling it the 

 sons labre. 



The name epipharynx was bestowed upon this organ by Savigny, 

 who thus speaks of that of the bees : " Ce pharynx est, a la verite, 

 non settlement cache par la levre superieure, mais encore exaetement 

 reconvert par un organe particulier que Reaumur a deja decrit. 

 C'est une sorte d'appendice membraneux qui est requ entre les deux 

 branches des machoires. Cette partie ayant pour base le bord 

 superieur du pharynx, pent prendre le nom <\! epipharynx ou 

 glosse." 



