Table <i. --Number of Insects and other organisms per square foot (0.092 m.^) collected in riffle 

 areas in Three Mile Creek before chemical treatment and 1 week and 6 weeks after treatment, and 

 on the same dates in Little Scarboro Creek (untreated control), Lake Michigan, We-i 



Organism 



Three Mile Creek 



Pretreatment 1 week 



6 weeks 



Little Scarboro Creek 



Pretreatment 1 week 



Insects : 

 Plecoptera 



Nemouridae 



Chloroperlidae . 

 Ephemeroptera 



Heptageniidae . . 



Baetidae 



Trichoptera 



Rhyaoophi lidae . 



Psychomyiidae. . 



Hydropsychidae . 



Hydroptilidae. . 



Brachycentridae 

 Coleoptera 



Elmdae 



Haliplidae 



Diptera 



Tipulidae 



Simuliidae 



Chironomidae. . . 



Tabanidae 



Rhagionidae .... 



Empididae 



Other; 



Other insects .... 



Other invertebrates 



Annelida 



Criistacea 



Isopoda 



Amphipoda 



Hydracarina 



Total 



Percentage of 

 pretreatment 

 number 





 



3 







6 



32 



17 











106 

 1 



1 

 1 

 ^2 

 1 

 

 

 

 



7 



29 



6 





 



1 

 



2 

 2 



15 

 

 



207 



1 



1 

 1 

 19 

 

 

 

 

 



15 

 5 



Number per square foot 



8 



1 





 497 



3 



13 



9 







105 

 



7 

 

 30 

 

 

 

 



1 





 10 



111 



5 





 18 



55 

 



U 

 

 



293 

 



5 

 1 

 15 

 

 1 

 2 

 

 





 87 



18 



1 

 



1 



u 



78 







25 











379 

 



7 

 1 

 9 

 



1 

 1 

 1 

 







55 



15 



1 





 55 



40 

 



11 

 



1 



544 

 6 



9 



14 

 23 





 

 5 

 



1 



10 





 65 



11 



277 



795 



520 



588 



(table 7); the total number was 40 percent of 

 the pretreatment sample. The decline of Hele- 

 idae was similar to those in sand and detritus 

 areas of Iron River and Sturgeon River (tables 

 5 and 6). The sannple taken 6 weeks after 

 treatment showed complete recovery; the total 

 number was 120 percent of the pretreatment 

 number. 



Buck Bay Creek was sampled in a riffle area 

 1 day before, and 1 week and 6 weeks after 

 treatment. The sample taken 1 week after 

 treatment showed only a small change in total 

 number of organisms. Chloroperlidae, Baet- 

 idae, and Lepidostomatidae were reduced 



somewhat; Chironomidae, Empididae, and 

 Annelida had increased; and other organisms 

 changed little (table 7), Treatment concentra- 

 tions and period of exposure to TFM (table 2) 

 were less than on most study streams; this 

 difference may account for the lesser reduction 

 in total number of organisnns. Organisnns were 

 abundant 6 weeks after treatment, when the 

 total was 137 percent of the pretreatment 

 number. 



A riffle area of Sunny Brook was sannpled 

 1 day before, and 1 week and 6 weeks after 

 treatment. The reduction in total number of 

 invertebrates after 1 week to 60 percent of the 



