MOUTH-PARTS OF THE MALLOPHAGA. 



131 



and Mallophaga indicate their affinity, and a plausible theory 

 has been suggested that the latter are Psocids which have 

 undertaken a parasitic existence. In any case the "glands" 

 and sclerite must be regarded as part either of their Psocid or 

 pre-Psocid inheritance, so that the typical oesophageal sclerite 

 and " glands " of the Ischnocera are older than the modifications 



Text-fig. 24. 



Hypopharynx and lingual glands of Lipeurusferox, X 186. 



A, oesophageal sclerite ; B, anterior cornu ; C, duct ; D, gland ; 

 E, anterior compound plate. 



described in the Amblycera, in spite of the fact that the Ambly- 

 cera by the possession of jointed palpi, by the form of the 

 alimentary canal, by the position of the mouth-parts which have 

 not shifted backwards, and in several other respects appear to be 

 the less specialised of the two suborders. 



9* 



