75 



chitinization and coloration of the parts. The head should 

 then be washed in water and removed to a watch glass con- 

 taining water. The mouth-parts can now be examined in situ 

 and finally readily dissected apart by means of dissecting 

 needles and forceps. 



The parts can be temporarily mounted in glycerine, or if 

 permanent mounts are desired, the parts can be mounted in 

 glycerine jelly. Carry from the water directly into the jelly. 

 For mounting in Canada balsam the parts must be thoroughly 

 dehydrated by carrying through successive strengths of alco- 

 hol up to absolute, and then clearing in xylol or other clear- 

 ing oil. 



BITING AND SUCKING MOUTH-PARTS. 



In the Hymenoptera, the mandibles retain their function 

 of biting, while the maxillae and labium unite to form an ap- 

 paratus for lapping or sucking liquids. Two examples of 

 this condition of mouth-parts fitted for biting and sucking 

 may be examined : a wasp, in which the maxillae and labium 

 are somewhat elongated and fitted for lapping ; and a honey- 

 bee, in which the maxillae and labium are much elongated 

 and fitted for sucking. 



MOUTH-PARTS OF THE WHITE-FACED HORNET. 



Vespa maculata ; order Hymenoptera. 



Because of the considerable membranous and fleshy tissue 

 of the mouth-parts, bleaching in KOH should not be carried 

 far ; a minute or two of boiling, sufficient for softening, will 

 do. In fact, simply softening in warm water-is perhaps safer. 



The mouth-parts of the wasps and bees are so thoroughly 



united at the base by the development of the pharyngeal 



skeleton and membrane that a considerable tearing of tissue 



is necessary to separate the parts. The mouth-structure as 



G 



