246 



INTRODUCTION TO ZOOLOGY 



CHAP. 



inhabitants of the pond, and hence are often called "Water 

 Tigers." They should never be brought home in a collecting tin 

 with other creatures. 



FIG. 172. Female Dyticus laying eggs in the stem of a rush in which her 

 ovipositor has made a longitudinal incision. (After Regimbart.) 



The general form and characteristic attitude of the larva is 

 shown in Fig. 173. The head is flat and bears six simple 

 eyes on each side. The mouth is peculiar, being merely a 

 horizontal slit between the upper and lower lips (labrum and 



labium), which is closed even 

 when feeding. On either side 

 of this is a curved sharply- 

 pointed mandible, having a 

 minute tube running through 

 it, open near the tip and again 

 at the base. 



The larva seizes its prey 

 with these jaws, and then 

 quickly closes them over its 

 mouth as far as possible. 

 This action brings the basal 

 opening of the tube into the 

 corner of the otherwise closed 

 mouth, and the blood of the 

 victim is sucked into the 

 FIG. 173. Full-grown Larva of mouth through the channel. 1 

 Dyticus marginalia with man- The larva feeds chiefly in this 

 dibles, m, extended. waVj t h ougn apparently it can, 



, Tail appendages which float on the water , ext ending its mandibles 

 surface when the beetle is breathing. . , , 



widely, open the narrow slit- 

 like mouth sufficiently to swallow small solid particles. 



1 For further details of the locking action of the mandibles, automatically 

 closing the mouth, see Miall, Aquatic Insects, pp. 45-47. 



