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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



the fulcrum, which supports directly the maxillae and the super- 

 linguae. The shape of this fulcrum will be discussed later. The 

 mandibles extend farther back than the maxillae, in fact nearly reach- 

 ing the hind border of the head (fig. 7) ; this shows that actually a 

 reciprocal movement of the mandibles and the maxillae must have 

 taken place, probably in connection with the rotation of the first and 

 second maxillae during embryological development. 



The pouch is distinctly seen behind the mandibles and the maxillae, 

 surrounding both ; it proceeds forward, but is interrupted in the 

 middle line, where the sternal parts of the head are coalesced with 



t'-.-cd. 



Fig. 6. — Campodca phisiochaeta Silv. Fulcrum, hypopharynx, and maxillae, 

 ventral. Maxillae dotted. 



the labium (see, for instance, Nassonow, fig. 28). The hypopharynx 

 (lingua and superlinguae) is situated below the maxillae. The pouches 

 extend very near to the side wall of the head (the plicae orales being 

 very narrow) in their entire course and are open to the lateral ex- 

 terior at the height of the maxillary palpi. 



As an example of the morphology of the mouth parts of Collembola 

 I shall give figures of Onychiurus armatus Tullb. (figs. 8-1 1) drawn 

 from the same sides as figures 4-7. They have been drawn pre- 

 viously several times, most beautifully by Borner (1908) ; cross sec- 

 tions are found in Nassonow (1887, fig. 56 anterior to the antennae 

 and fig. 57 in the middle of the head) and in Denis (1928), who also 

 describes other species of collemboles. Beautiful cross sections are 



