434 SYNOPTIC COLLECTION. 



The larva of Amphizoa /AY?/;/*/ Matth., (PI. 1079, fig. i, 

 dorsal view; fig. 2, ventral view) is Thysanuriform in 

 general aspect and is strongly chitinous above. When 

 the larva is extended, the body is much longer and resem- 

 bles the larvae of the Carabidae. The larva and adult 

 live along the sides of rapid mountain streams, floating on 

 sticks in eddies or crawling among stones. " It gives the 

 impression," says Hubbard, 1 "of a terrestrial beetle with 

 amphibious or semiaquatic habits." 



Dytiscus is a water beetle whose larvae (PI. 1080, fig. 

 i, D. marginalis Ahr.) breathe by means of two spiracles 

 at the end of the abdomen. The air is taken in at the 

 surface of the water, as is also the case with the adult 

 (No. 1081, D. verticalis Say, dorsal side; No. 1082, ven- 

 tral side) which stores its air away under the wing covers. 



The larva is remarkable for having primarily solid 

 mandibles modified into hollow organs (PI. 1080, fig. 2, 

 showing the opening at the smaller end) through which 

 the juices of its prey are sucked. Here, then, we have 

 a mandibulate type of insect converted into a suctorial 

 type. 



The Gyrinidae are also aquatic beetles in both the lar- 

 val and adult states, and possess other specializations for 

 such a habitat. Along each side of the abdominal seg- 

 ments of the larva (PI. 1083, Orectochilus villosus O. F. 

 Mull.) there are branchial organs used for respiration and 

 locomotion. The adults (No. 1084, Gyrinus) are usually 

 seen upon the surface of the water swimming by means 

 of their paddle-like feet. They are provided with a pair 

 of eyes that are divided in such a way that it is thought 

 that one part looks upward into the air (PI. 1085, fig. i, 

 dorsal view) and the other part downward into the water 

 (fig. 2, ventral view). 



The long, flattened larvae of the Silphidae or burying 

 beetles (PI. 1086, Necrophorus tomentosus Web.) feed upon 



1 Proc. Ent. Soc. Washington, II, no. 3, 1892, p. 344. 



