1 1 8 Invertcbrata. 



so that in acting they move in a horizontal plane. 

 The upper pair are named mandibles or biting jaws, 

 the lower pair maxillae or chewing jaws. The last- 

 named have usually appended to them on each side 

 a pair of small jointed feelers or maxillary palps. In 

 the bluebottle and house-fly the lower lip is lengthened 

 into an elongated gutter-like sheath in which are con- 

 tained the maxillae and mandibles, which are reduced 

 to mere bristle-like processes. 



In the bee (fig. 77, p. 132) the upper lip and 

 mandible are strong and fitted for chewing, while 

 FlG . 6 7 . the maxillae and lower lip are long 



and channelled, so that when 

 placed in apposition they make 

 a tube through which the insect 

 sucks in honey. In these crea- 

 tures the lower lip consists of 

 two parts, an upper or tongue 

 and a hinder part or nientum. 

 In the butterfly, the mouth has 

 lost all trace of its chewing func- 

 tion and the maxillae form two 

 half tubes, and when opposed as 

 and the labial palps on each they always are they make up a 



si'^e of the antennae and J J 



between the eyes. canal, and being very long and 



curved, this is sometimes called the proboscis. Each 

 of these maxillae has within it also a fine tube, and thus 

 a transverse section through the proboscis shows three 

 tubes, one medial between the maxillae and one lateral 

 on each side within each maxilla. Behind this proboscis 

 lies the labium, which has usually large palps between 

 which the proboscis lies when retracted ; for, unlike 

 the tube in the bee, this proboscis is freely retractile. 



