HOW TO KNOW THE IMMATURE INSECTS 



10a. Head nutant; mandible falcate and simple; 8th abdominal spir- 

 acle absent. Fig. 179 Family HYGROBIIDAE 



This is a small family comprising 

 all aquatic species. They are found 

 in the Eastern Hemisphere. 



Fig. 177. Hydrobia tarda Herbst. 

 (Redrawn from Boving and 

 Craighead) . 



10b. Head porrect; mandible not simple; 8th adbominal spiracle ter* 

 minal. (See Fig. 178) II 



11a. Mandible with distinct retinaculum, inner margin neither sulcate 

 nor tiibular; legs fossoriaL 

 Fig. 178 Subfamily Noterinae, DYTISCIDAE 



^ ^ The members of this small sub- 

 family ore rather minute in size. 

 r r f CL Their larvae must feed, of course. 



Fig. 178. o, Noferus sp.; b, mandible. On tiny animol formS. 



lib. Mandible without distinct retinaculum, inner margin either sul- 

 cate or tubular; legs ambulatory or natatory. 

 (See Fig. 179) 12 



1 2a. Prothoracic presternum large and subquadrate; gtUa present, sub- 

 quadrate or triangular; gular suture double or anteriorly biiui^ 

 cate. Fig. 179 Family DYTISCIDAE 



Fig. 179.. a, Dytiscus sp.; 

 b, Ventral aspect of head. 



The family contains more than 2,000 spe- 

 cies. Their adults are known as predacious 

 diving beetles, water beetles and dytiscids. 

 The larvae are predacious and feed upon 

 many kinds of aquatic animals including 

 moUusks, worms, tadpoles, salamanders and 

 fishes. Because the hunting life, the larvae 

 are sometimes called water tigers. Their 

 pupae ore terrestrial and pupation takes 

 place above the water line. 



77 



