78 THE LARVA OR NYMPH [CH. 



to one another like the thumb and forefinger, and serve to grip 

 the prey. The sub-mentum (sm), in the position of rest, is directed 

 backward along the ventral surface of the thorax, between the 

 bases of the legs. At its distal end it bears a strong hinge (h), 

 which functions as an elbow- joint, and serves to articulate the 

 mentum. The mentum (m) lies ventrally below the sub-mentum, 

 but is directed forward, so that its distal end lies just below the 

 mouth. Lateral squames are absent. Galea and lacinia are 

 absent or vestigial, but the base of an original ligula is represented 

 by the median lobe (ml), which is fused with the mentum, and forms 



ih 



Fig. 30. Concave or spoon-shaped mask of Synthemis eustalacta Burm. d toothed 

 distal border of lateral lobe; m men turn; mh movable hook ; sm sub-mentum. 

 ( x 8.) Original. 



its mid-anterior border. Movably articulated with the mentum, 

 on either side of the reduced median lobe, is a strong lateral lobe 

 (II) formed by the palp. These two lateral lobes are very highly 

 specialized, and form the actual organ of prehension. Each 

 carries, at its outer distal angle, a strong movable hook (mh). The 

 end-hook of the imaginal labium, which is fixed, is represented in 

 the labial mask by the apex (a) furnished with a small hook in 

 some forms, but not in most. The presence of a movable hook 

 and an apex enables us to divide the margin of the lateral lobe into 

 three portions, whose different degrees of development in the 

 various groups lend to them considerable taxonomic importance. 



