Mangan, ]\Iaxilluh2 ifi Larvce of Dytiscida. 



depression of which subserve the increased efficiency of 

 the interlocking arrangement. 



Duges (2), in describing the larva of Cybister fimhrio- 

 laius, Say, called attention to a small process at the base 

 of the mandible : — " A la base de la mandibule on 

 "apercoit iin petit corps paraissant cylindrique, courbe 

 " sur lui-mcme et arrondi a I'extremite ou il semble 

 " papuleux et que nous croyons etre le representant des 

 " lobules maxillaires." Duges was evidently under the 

 impression that in this larva there remained nothing of 



Fi^. 2. Mouth parts of larva referable to the genus Ilylius, 

 seen from above. 



la, kibium ; w, right maxilla ; .r, processes homologous with 

 maxillulre. x 40. 



the maxilla but its palp, and so suggested that the above 

 body at the base of this palp might represent the galea 

 and lacinia of the maxilla, but the nature of the maxilla 

 in the larvae of other genera of the Dytiscidiv renders such 

 an interpretation a very doubtful one. Meinert (3) figures 

 the mouth parts of an undetermined exotic species of 

 Cybister, recording the presence of a similar body which 

 he emphatically points out can have no connection with 

 the maxilla, and which he refers to the mandibular 

 segment. However, Meinert also notes that the ventral 



