OF MAXILLUL^E in the orders of insects. 



435 



carry bristles, and are continuous behind, as thin rods, round the opening of, 

 the salivary duct ; . . . The position of: . . . (Z) is conformable with the 

 idea that they may represent a pail of maxillulae." Sehimmer (39) describes 

 the hypopharynx of the Gryllid MyrmecopMla. On the ventral surface are 

 borne a pair of elliptical plates covered with fine setae. Mjoberg (34) has no 

 hesitation in homologising these plates with the so-called " lingual glands " 

 associated with the hypopharynx of Psocida?. The nature of these latter 

 structures will be discussed below, but here it may be remarked that 

 Enderlein (15) regards them as maxillula?. 



EPHEMERID.E. 



As the well-known figure of the lingua and superlingua? of Heptagenia 

 Vayssiere (45) makes evident, these structures attain a very well-developed 

 condition in the Ephemerida?. No attempt had at that time been made to 

 homologise the lateral appendages with maxillula?. Vayssiere was, however, 



Text-iia-. 4. 



m.p. 



Chloeon dipterum. Tongue of nymph, x 90. a. Articulation of maxillula. k. Hypo- 

 pharynx. m. Maxillula. m.p. Plate iu ventral wall of maxillula. p. Transverse 

 sclerite at base of maxillula. r, ei. Setose ridges at base of hypopharynx. 



so much impressed by their appendicular appearance that he proposed to 

 regard the Ephemeridse as insects provided with a secondary labium, con- 

 sisting of the median "langue" together with its "deux appendices." 

 Eaton, in his monograph of 1883, figures the " tongue " and " paraglossse " 

 of the nymphs of a large number of Ephemerida?. Though the latter organs 

 show considerable variation in size relative to the former, they are never 

 wholly absent. Hansen (21) refers to them as maxillula;. This view of their 

 nature is supported by the figure of the head of a young larva of Ephemera, 

 in which Heymons (23. Taf. ii. fig. 2D) clearly shows that they are originally 

 distinct from the hypopharynx. Erom his description (p. 22) it is evident 

 that Heymons regards the appendages as lateral portions of the hypopharynx. 



