NO. 3 INSECT IIEAID SNODGRASS 47 



lip beneath the mouth opening. The lateral lobes are best developed 

 in the more generalized insects, both apterygote (fig. 21 D. Ilphy) 

 and pterygote (fig. 20 A), and in coleopteran larvae, but possible 

 traces of them are to be found in many of the higher orders. The oc- 

 currence of the hypopharyngeal lobes has been w^ell reviewed l)y 

 Crampton (1921a) and by Evans (i92i),and those of lepidopteran 

 larvae have been described by de Gryse (1915). The median lobe of 

 the hypopharynx is best distinguished as the lingua, though some 

 writers call it the " glossa " ; the lateral lobes have been termed " para- 

 glossae " and " maxillulae," but Folsom (1900) has given them the 

 more distinctive name of superlinguae, because the lateral lobes of the 

 labium are commonly known as the paraglossae. 



The nature of the superlingual lobes of the hypopharynx has been 

 much discussed. Hansen (1893) proposed that they represent the 

 first maxillae, or maxillulae, of Crustacea, and Folsom (1900) be- 

 lieved that their identity as such was established in the discovery of 

 what he regarded as a corresponding pair of ganglia in the embryonic 

 head of Anurida. Crampton (1921a), on the other hand, argued that 

 the superlinguae of insects must be the homologues of the paragnatha 

 of Crustacea, and it will be shown later in this paper that the identity 

 in the relations of each of these organs to other structures of the head 

 can leave little doubt of the truth of Crampton's contention. The super- 

 linguae, then, are not the first maxillae of Crustacea ; but if the 

 superlinguae represent a segment in the insect head, the paragnatha 

 have a like significance in the crustacean head. It now appears prob- 

 able, however, that neither of these organs has a segmental value, 

 since Folsom's claim of the presence of a pair of superlingual ganglia 

 has not been verified by subsequent research, and Hofifmann (1911) 

 appears to have demonstrated that in the collembolan, Tomocerus 

 plumheus, the superlinguae are derived during embryonic develop- 

 ment from the inner basal angles of the mandibles (fig. 20 C, Slin) . 



In the Chilopoda and Diplopoda there is a single median hypo- 

 pharyngeal lobe forming a projecting lip below the mouth opening 

 (fig. 21 A, B, C, Hphy). In the Crustacea, the paragnaths usually 

 lie to each side of the median line, and are associated with the first 

 maxillae, but in some forms, as in Gammarus, they are united on a 

 common median base, forming a bilobed structure very similar to the 

 hypopharynx of the apterygote insect Japyx (fig. 21 D). 



The base of the hypopharynx is supported anteriorly, in generalized 

 insects, by a pair of chitinous plates or bars that extend laterally at 

 each side of the mouth, and form a suspensorial apparatus for the 



