130 MR. B. F. CUMMINGS ON THE 



immediately above the labium in front of the mouth and not 

 below the oesophagus, and on this account Snodgrass gives the 

 term hypopharynx only to certain setose lobes he found in 

 Lcemobothrium gypsis which actually overlie the labium. A 

 similar arrangement of lobes is seen in L. titan, where, as the 

 anterior area of the hypopharynx, they are in close relation with 

 the sclerite and "glands" — the elaborate posterior ai-ea. The 

 Ischnocera possess an anterior area — the true hypopharynx of 

 Snodgrass — in the small encompassing plate mentioned above, 

 which is much reduced in correspondence with the fact that in 

 the Ischnocera the whole labium has been shifted backwards so 

 as to leave the large mandibles a free field. In some genera of 

 the Amblycera such as Boopia or Heterodoxus the anterior area, 

 in which, as in Lcemohothrium, the " ducts " are incorporated, is 

 so large as to extend not only as far as above the labium but 

 even beyond it as two lobes protruding from the mouth {cf. 

 Mjoberg (7), p. 22). The two areas run into each other without 

 any dividing line. 



Varieties of Sclerite and Glands. 



I shall now discuss the various forms the hypopharynx assumes 

 in the different genera of the Amblycera. Modification begins 

 with Lcertiohothrium (see diagram, text-fig. 25, p. 132), in which 

 the sclerite is elongated and the anterior cornua very long, 

 extending almost up to the bifurcation of the " ducts." The 

 " glands " are less developed. The posterior cornua are present. 

 In Gyropus the main " nucleus " of the sclerite has disappeared, 

 the anterior cornua are fused at the base, and the posterior 

 cornua are longer and the "glands" very much reduced. In 

 Trinofon, the "glands" as such have quite disappeared, but may 

 here be represented by the lateral pieces, the bifurcating sclerite 

 being the broadened " duct." * The anterior cornua are entirely 

 fused together. In Ancistrona procellarioi the anterior cornua 

 are quite distinct but ad pressed closely against the broad rami ; 

 each of the rami bears in front a rounded plate with a strongly 

 serrate edge corresponding with the anterior area of the hypo- 

 pharynx. The diagram is intended to show the probable 

 evolution of the structure in the Ischnocera and Amblycera. 



The presence of oesophageal sclerite and " glands " in the 

 Psocidse as well as in the Mallophaga points to the antiquity of 

 the structures. Several features in the anatomy of the Psocidse 



* In Dochopliorus spJienophorus (text-fig. 27), an Icshnoceran, the ducts are so 

 minute and delicate as to suggest atroph}'. In front, they are accompanied and 

 supported by a forked piece of chitin , and in other species and genera the duct 

 is clearly seen to be accompanied along its course by chitin, so that in those 

 forms where the ducts qna ducts are absent their former course along the bottom 

 of the pharynx may be traced in the track of persisting chitin which they leave 

 behind. It is this forked piece of chitin, rather than the duct itself perhaps, which 

 is homologous with the bifurcating sclerite in Trinoton (text-fig. 29, B) and other 

 genera. 



