OF MAXILLULSE in the orders of insects. 45.5 



hypopharynx. In the Ephemeridse the maxillulsa lie between the mandibles 

 nnd maxillae, though they are articulated to the base of the hypopharynx. 

 In larvae of certain Perlaria Filipalpia I find structures projecting from the 

 sides of the hypopharynx, which bear comparison with the maxilluke of 

 Ephemeridse. In the section Setipalpia these appear to be represented by 

 small setiferous convexities on the surface of the hypopharynx. My investi- 

 gations do, I believe, tend to support the view that partially fuse 1 maxillnlse 

 may be recognised in the membranous lobes associated with the hypophnrynx 

 in Psocida? and certain Mallophaga, and that the so-called "lingual glands" 

 are chitinizations of the ventral wall of the hypopharynx. 



In the Endopterygota the presence of maxillulse is established in four 

 families of Oo!eoptera. I have described structures which I regard as 

 possibly homologous with these appendages in Elatoridse, Staphylinidse, 

 Telephoridse, ( !occinellid;e, and Tenebrionidae. Reference has been made 

 to others of a more doubtful nature in Doryphora and Otiorhynchus. 



The hypopharynx of Trichopterous larvae bore comparison with that of 

 Lepidoptera. On its dorsal surface were structures apparently homologous 

 with the maxillulae of Lepidoptera. Larvae of Sialis and Chri/sopa did not 

 appear to possess these appendages. In the adults of species of these two 

 genera of Neuroptera and in Raphidia the hypopharynx bore lateral struc- 

 tures which, from comparison with Forficula, seem to be wholly or partially 

 maxillular in nature. Similarly located lobes, though modified in form, occur 

 in larval Tcnthredineae. 



Attention has been called to the, presence of a pair of projections associated 

 laterally with the hypopharynx of two Nemoceran Diptera, Bibio and 

 ( 'hironomus. It is doubtfully suggested that these are of the nature of 

 maxillulae. 



A comparative review of the various conditions of the hypopharynx and 

 maxillulaa of insects from the Aptervgota to the most highly specialised 

 mandibulate Pterygota, points to the existence of a tendency to modification 

 along certain lines, as follows : — 



(1) Greater association of the maxillulae with the hypopharynx. (Com- 



pare Lepisma with Machilis, Blatta, and Forficula ; Perlodes 

 with Nemiira). 



(2) Reduction in the size of the maxillulse. 



(3) In Exopterygota the formation of a compound ''tongue" composed 



of the hypopharynx and rnrtxillulse carried by a forward ly pro- 

 duced portion of the mouth-floor, specially developed lor the 

 purpose. This is seen in an incipient condition in Chlveon and 

 Nemura. It is well Formed in Forficula, Blattidae, and probably 

 in Psocidre. 



