FIG. B S [a] External (satures of 

 a cadditfly larva: (b) larva 

 and case from a weedy lake; 

 (c) larva and caje from a 

 spring-fed brook (courtesy Illinois 

 Natural History Survey). 



FIG. 5-6 Immature stages of th 

 black fly: (a) larva: |b) pupa: 

 (c) pupa case (Shelford 1913 

 after Lugger); (d) enlarged 

 detail of arrangement of hooks 

 on the posterior end of the 

 larva (after Nielson 1950) 



FIG. 5-7 Water pennies, larva 



of the psephenid beetle: (a) dorsal 



(Shelford 1913); and (c) larva 

 of the net-veined midge; showing 

 the central row of six 

 suckers (after Mora 1930). 



Streams 



