OF THE WATER-BEETLE PELOBIUS TAKDUS. 97 



Plate III. 



Figs. 1 & 2 are from sketches of the positions adopted by the larva at work when 



constructing its cell. 

 Fig. 3 shows the position of the larva resting in the completed cell, waiting to 



change into a pupa. 



Fig. 4. Ventral view of a third-stage larva, showing the gills on the left side of the 

 thoracic and right side of the abdominal segments, the others having 

 been omitted for the sake of clearness. This diagram is based upon a 

 camera lucida drawing, Cc=Coxal cavitj'. Sp=the closed meso- and 

 meta-tlioracic spiracles. 



Fig. 5. A diagram of one of the glass cells used to enable the work of cell con- 

 struction by the larva to be watched. 



Fig. 6. Under side of the right elyrron of a male specimen of the beetle to show the 

 iile, upon which the apex of the abdomen rubs to produce the "squeak." 

 There is a tile on each elytron, and the files are alike in the two sexes. 



Proc. Zool. Soc— 1922, No VIT 



