;6 OUR HOUSEHOLD INSECTS 



are capable of lateral movement. Tracing them back to 

 their point of attachment to the head, we find that the 

 basal part is of a somewhat more substantial character 

 than the terminal, and that at the junction of the two 

 parts, on the outer margin, each maxilla carries a 

 slender six-jointed appendage, the maxillary palpus. 

 When the maxillae are moved aside, a single central 

 organ, previously partly covered by them, comes into 

 view; in its front part it is thin, flat, and band-like, 

 but behind it is much thicker. This is the labium 

 or so-called tongue. The flat portion is rather deeply 

 bifid in front, and carries two narrow organs, the 

 paraglossse, attached to its sides, but not quite reach- 

 ing the tip ; thus the free edge of the labium presents 

 four rounded divisions. Further back it carries two 

 jointed appendages, the labial palpi ; they are stouter 

 than those of the maxillae, and are only four-jointed. 

 It is this tongue that the insect uses as a trowel in 

 its plastering operations, when it is manufacturing its 

 nest. When the mandibles are closed, they almost 

 entirely conceal all this mechanism, only the tips of the 

 palpi being visible. 



From the above description it will be evident that a 

 wasp's head is not quite so simple an object as it might 

 at first sight appear; nevertheless, there is no great 

 difficulty in making out for one's self all the above 

 points. Only two tools are necessary, a needle to open 

 out the mouth organs, and a hand -lens to examine the 

 different parts. The examination is best conducted on 

 an amputated head. The junction between head and 

 thorax is so slight that there is no difficulty in decapitat- 

 ing a wasp (a dead one, of course !), and if a stout pin or 

 the end of a match cut down to a point be inserted in 

 the small hole that will be found at the spot where 



