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THE PRESENCE OF MAXILLUL^ IN BEETLE LARV^. 



By George H. Carpenter, Royal ColleCxE of Science, 



Dublin. 



It is nearly twenty years ago since Hansen (1893) called 

 attention to the morphological importance of the maxillulae — 

 a minute pair of structures recognisable in the Apterygote 

 insects on the anterior or dorsal surface of the tongue or 

 hypopharynx, with which they are articulated or partly fused 

 basally. Hansen insisted on the appendicular nature of these 

 maxillulœ, considering them as serially homologous with the 

 jaws and as corresponding with the first maxillae of Crustacea. 

 Evidence in favour of this view has been brought forward by 

 FoLSOM (1900) and others, so that it has now been accepted 

 by a considerable number of students of the Arthropoda. 



Naturally attempts have been made to recognise the 

 maxillulae in winged insects. Hansen certified their presence 

 in Dermaptera and Orthoptera ; Folsom and others have 

 shown that they form the conspicuous lateral lobes on the tongue 

 of Ephemerid larvae and nymphs, while Borner has called 

 attention (1904) to their existence in the Copeognatha (Psocidae). 

 The fact that these structures are most easily recognised in the 

 Apterygota, and in such primitive Pterygota as the Ephemeridae 

 (Mayflies) and the Dermaptera (Earwigs and Hemimerus), 

 suggests strongly that their presence may be regarded as an 

 archaic feature, and the question arises whether they can be 

 recognised at all in any of these more highly organised insects 

 that pass through a " complete " transformation (Endopterygota 

 of Sharp). Hansen mentions that he could find no trace 

 of them in the Coleóptera. 



With regard to beetles in their adult condition, it is likely 

 that no investigator will succeed where Hansen has failed. 



