246 



INTRODUCTION TO ZOOLOGY 



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 R^gimbart.) 



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.^ 



Dyticus inarginalis with man- The larva feeds chiefly in this 



dibles, m, extended. ^^^^ ^jj^^gj^ apparently it can, 



(.Tail appendages which float on the water , pxtendinsr its mandiblps 

 surface when the beetle is breathing. "1 exienamg Its manOlDies 



widely, open the narrow slit- 

 like mouth sufficiently to swallow small solid particles. 



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

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



