MOUTH-PARTS OF THE MALLOPHAGA. 



139 



; Pkysostomum sp. ? mystax.— The "glands" are present but 

 appear to underlie the ducts, with which I cannot find their 

 point of attachment. Only one rather poor specimen formed 

 my available material for dissection in this species. The anterior 

 cornua are very long and curl round in front (text-fig. 32). 



Text-fig. 32. 



Physostomum sp., X 219. 

 A, oesophageal sclerite; B, glands; C, rami; D, anterioi' cornu. 



The Maxillary Forks. 



These problematic " forks " ai"e delicate chitinous rods un- 

 connected with the rest of the mouth-parts, but lying within the 

 mouth, one on either side of the hypopharynx. They have been 

 recorded from A. gigas P., Goniodes dissimilis N., LcEmoboihrium 

 gypsis Kell. I find them present in Tetrophtalmus titan P. (text- 

 fig. 28, E), Lcem. titan P., Trinoton luridum N". (text-fig. 29, F). 

 On accovint of their fragile nature they may easily be overlooked, 

 and therefore perhaps exist in many other species. It is tempting 

 to look upon these " forks " as the maxillulje or super-linguse of 

 the hypopharyngeal or fifth segment of the insect head. A 

 third pair of maxillfe are present and well developed in many 

 Apterygota, and recently Prof. G. H. Carpenter and Miss Mabel 

 MacDowell have made a further contribution to the question of 

 the serial homologies of the insect head by a paper (1912) (10) on 

 the mouth-parts of certain beetle larvse, where the maxillulse are 

 represented, it is suggested, by the side pieces of the hypopharynx. 

 This question in the Mallophaga is worth investigation. An 

 alternative suggestion is that the maxillary forks are the inner 



