THE MOUTH PARTS OF CIMEX 501 



one of which conveys the food from the wound to the pharynx, while the 

 other conveys the saliva in the reverse direction. The condition is com- 

 parable to that found in the fleas (page 438). 



Each mandible is a long thin slip of yellow chitin, bent upon itself 

 about its middle, the position of the bend corresponding to the point of 



emergence of the proboscis from the head. The 



i ir i- -1-11J1 The mandibles 

 proximal portion, therefore, lies within the head, the 



distal portion in the groove on the dorsal surface of the labium. The 

 proximal portions lie on each side of the pharynx, diverging from one 

 another posteriorly, and have two pairs of muscles attached to their swollen 

 basal parts; one of these pulls in an anterior direction, and may be 

 termed the protractor, while the other pulls in a posterior direction, and 

 may be termed the retractor. The two mandibles come in contact with 

 one another at the anterior end of the pharynx and immediately in front 

 of the salivary reservoir, and from this point forwards the blades are 

 flattened and strongly concave on their internal aspects, the two together 

 forming the walls of a canal with a circular lumen (Plate LXII, fig. 4). 

 The posterior wall of this canal is much thicker than the rest, and at the 

 point in the middle line where the two mandibles are in contact with 

 one another there is a semi-circular notch on each, the two notches 

 together forming a circular channel through which the saliva passes 

 downwards (Plate LXII, fig. 4). External to the groove the mandible 

 is reduced in thickness, to expand again in the lateral area, where there 

 is a small space, running the whole length of the organ, in which is 

 contained some cellular tissue for the nourishment of the chitin of the 

 blade. Anteriorly the blades are very thin, and it is not possible to 

 determine, in sections, the line of demarcation between them. In dis- 

 sections the two mandibles frequently remain adherent to one another by 

 their anterior borders. 



At the distal end (Plate LXII, fig. 2) the mandibles are broadened 

 out into flanges which interlock with one another, the opening between 

 the two blades being the prestomum. 



The maxillae are the cutting weapons with which the bug makes the 

 wound in the skin. They resemble the mandibles very closely in shape 

 and disposition, lying dorsal and external to them in The maxj| , ae 

 the head, and external and closely apposed to them in 

 the proboscis. The swollen basal part has attached to it a chitinous rod 

 which extends backwards to the posterior part of the head, and which 

 probably corresponds to the stipes; strong retractor and protractor muscles 

 are inserted into it and into the basal part of the maxilla proper. At the 



