MOUTH-PARTS OF THE MALLOPHAGA, 129 



them to the labium. Snodgrass (1896) (4) followed suit, but 

 in 1905 (5) retracted in favour of Nitzsch, as the result of 

 examining preparations of Ancistrona gigcis P, and Lcsmoho- 

 thrmm gypsis Kell., in which the stipes of the palpus was seen 

 to be separate from the labium. 0. O. Waterhouse (1904) (6) 

 had already illustrated the fact that in L. titan P. the palpus 

 was connected with the maxilla by a delicate hand of connective 

 chitin. I have discovered similar slips not only in L. titan, 

 but in Ancisti-ona procellarice Westwood (text-fig. 25, p. 132) 

 and in Nitzschia pulicaris IST. 



The (Esophageal Sclerite and Lingual Glands. 



These structures are unique in the comparative anatomy of 

 the insect mouth. They occur in their typical form in the 

 Ischnocera. In the other suborder it is customary to say that 

 they are either modified or absent, but, as I show below, they 

 are really present in all the Amblycei-a with the possible 

 exception of Latumcephalum, which was not available for exami- 

 nation. The oesophageal sclerite and glands in the Mallophaga 

 were first discovered by Snodgrass (4). They are unusually 

 difficult of dissection in the Amblycera on account of their 

 delicacy and minuteness and their position below the oesophagus, 

 having regard to the flatness of the head in the Mallophaga as a 

 whole. 



The sclerite in the Ischnocera is of a densely chitinous character, 

 usually quite visible through the integument lying in the lower 

 wall of the oesophagus behind the labium. There are two 

 anterior cornua and sometimes a posterior pair, but these are 

 absent in L. ferox G. (text-fig. 24, p. 131). Lying longitudinally in 

 the doi'sal wall of the oesophagus immediately above the sclerite, I 

 find in Goniodes falcicornis and in Lipeurus ferox a long, narrow 

 chitinous splint. Towards this, the posterior cornua in G. falci- 

 cornis curl up the sides of the oesophagus. 



The lingual glands are hard, flat, oval pieces of chitin in which 

 no glandular structure can be detected, though they still await 

 histological examination. In L. ferox and G. falcicornis, if not 

 in most other Ischnocera, the anterior ends of the two glands are 

 encompassed by a small compound plate of chitin (text-fig. 24, E), 

 narrowing towards the edge of the labium. A curious duct, 

 cross-barred like a trachea, arises from the sclerite and runs 

 forward, where it bifurcates, one ramus (or " bronchus ") entering 

 each of the glands. My own dissections lead me to agree with 

 Mjoberg (1910) (7) and Grosse (3), who regard the "glands" as 

 chitinous and as part of the sclerite, the whole to be regarded 

 as a compound hypopharynx *. Normally the hj^popharynx lies 



* A central canal is almost certainly present in the ducts of some, but its 

 meaning remains problematical, unless we suppose that a kind of chitinous 

 sclerosis has overtaken real glands and ducts, until finally, in such genera as 

 Ancistrona and Trinoton (text-figs. 26 & 29), the original structures have become 

 obliterated and replaced by chitin. 



Proc. Zool; Soc— 1913, No. IX. 9 



