Beetles 



221 



larvae and adults are of very different appearance. 

 Beetle larvee most resemble certain neuropteroids of the 

 family Sialididfe in appearance, and there is no single 

 character that will distinguish all of them (see fig. 121 on 

 p. 214). Only a few beetle larvae (Gyrinids, and a few 

 Hydrophihds like Berosus) possess paired lateral fila- 

 ments on the sides of the abdomen such as are charac- 

 teristic of all the Sialididas. 

 Aquatic beetle larvsc are 

 much like the larvae of the 

 ground beetles (Carabidae) 

 in general appearance, hav- 

 ing well developed legs and 

 antennae and stout rapacious 

 jaws. 



Best known of water 

 beetles are doubtless the 

 "whirl -i- gigs" (Gyrinidae), 

 which being social in their 

 habits and given to gyrating 

 in conspicuous companies on 

 the surface of still waters, 

 could hardly escape the 

 notice of the most casual ob- 

 server. Their larvae, how- 

 ever, are less familiar. They 

 are pale whitish or yellowish translucent elongate crea- 

 tures, with very long and slender paired lateral ab- 

 dominal filaments along the sides of the abdomen. 

 They live amid the bottom trash where the}^ feed upon 

 the bod}^ fluids of blood worms and other small 

 animal prey. Living often in broad expanses of sho.al 

 water where there are no banks upon which to crawl 

 out for pupation, they construct a blackish cocoon 

 on the side of some vertical stem just above the surface 

 of the water and undergo transformation there. The 



Fig. 129. A diving beetle, 

 Dytisciis, slightly enlarged. 



