46 NATURAL HISTORY OF AQUATIC INSECTS CH. 



When the mandible is extended, its basal opening is 

 outside the mouth, but when it is closed the basal 

 opening is brought into the corner of the mouth, and 

 then the larva sucks up the blood of its victim as a 



FIG. 6. Structure of mouth of Dytiscus larva, i. The mandibles, one extended, 

 the other closed. 2. Section of mouth-lock ; ;;*, mouth. 3. Section through 

 mouth and pharynx ; Ibm, labium ; nil, mouth-lock ; ;, mouth ; ph, pharynx ; 

 fin, put, muscles. From Burgess. 



man might suck up water through a straw. It is 

 easy, he adds, to open the mouth with a pair of for- 

 ceps. The fitting must be extremely good. Mr. W. 

 F. Baker tells me that when a Dytiscus larva pre- 

 served with alcohol is placed in strongly heated 



