362 



Aquatic Societies 



A DIAGRAM OF LOCALIZATION OF INSECTS IN 

 THE BED OF A SWIFT STREAM 



(From Needham and Christenson, ^2'j) 



surface 



bottom 



Twelve situations about a boulder, and the insects commonly found in 

 them in Logan River, Utah, are as follows: 



1. Simulium; black fly larvae; fully exposed where current is swiftest. 



2. Brachycentrus; caddis worms; in square cases attached by the upstream 



end. 



3. Bibiocephala ; net- winged midge-larvae; of limpet-form, adhering by 



ventral suckers. 



4. Glossosoma; caddis worms, in pebbly cases on down-stream face of 



boulders. 



5. Antocha; carnivorous cranefiy larva; in tubes on down-stream face of 



boulder. 



6. Hydropsyche; net-spinning caddis worm, making nets beside a crevice 



where water breaks over. 



7. Atherix; snipe fly larva, living in crevices. 



8. Baetis and Leptophlebia; mayfly nymphs, living on bottom in slackened 



current. 



9. Iron and Rithrogena; mayfly nymphs, clinging to broad surfaces, mostly 



underneath. 



10. Chironomus and Tany tarsus; midge larvae, living in tubes in more or 



less exposed places. 



11. Ephemerella grandis, the prickle-back mayfly nymph; clinging to trash 



in half sheltered places. 



12. Acroneuria and Pteronarcys; stonefly nymphs; living amid the trash and 



sheltered by it. 

 The arrow indicates direction of the current. 



