NOTES ON THE MOUTH-PARTS OF LICE. 



512 



It is possible that a further examination of American marsupials in the field will produce a variety 

 of interesting forms, which may support the suggestion made here as to the possible origin of Ambly- 

 ceran parasites of American mammals from parasites of the marsupials. More pertinent to the present 

 discussion is the fact that two of these forms, while still possessing mandibulate mouth-parts, exhibit 

 a condition in which the mandibles have undergone at least a partial loss of function, and have become 

 enclosed within the buccal cavity. I have shown (1916) that mandibles are present in young Body-lice, 

 and that they persist even in the adult stage in some lice of seals. I do not. of course, suggest that 

 Philandesia and its newly-discovered ally are stages in the line of descent of the sucking lice from their 

 mandibulate relatives. But these two biting lice seem to me to afford some evidence of how a transi- 

 tion from the biting to the sucking type may have taken place. 



l.h. ail. 



Another insect which must be taken into consideration is the elephant-louse Haematomyzits 

 elephant is Piaget. This insect is, in most of its characteristics, a typical sucking louse. Its position 

 has never been called in question, such extreme modifications as it does show on a superficial examina- 

 tion being attributed as adaptations enabling it to live on its particular host. But an examination of 

 the mouth-parts of Haematomyzits (Text-fig.) shows at once that these differ very markedly from those 

 of all other sucking lice. 



Unfortunately my only material of this louse comprises a male and a female cleared in potash and 

 mounted. I am unable, in consequence, to examine the mouth-parts in section ; but certain out- 

 standing features can be clearly made out in the mounts. 



Fig A. represents the proboscis and forepart of the head of Haematomyzus, magnified 100 diameters, 

 the bases only of the antennae being indicated. The only chitinous structure appearing in the lumen of 

 the proboscis is the narrow siphon, or sucking-tube (si.), which is continuous behind with the pharynx 

 [ph.). There is no trace of any such diverticulum as occurs in all other Siphunculata, with its contained 

 piercing organs which Enderlein homologises with hemipterous mouth-parts. 



