456 



Notes ox the Stecies of Ixsects Collected 



Plecoptera 



As stated elsewhere in this paper, stone-fl}- naiades are notable inhah 

 itants of rapids and well-aerated streams. In the present collection none 

 were found except in clean water. The majority of specimens discovered 

 in 1921 were species of the genus Pcrla. Ptcronarcys was found only in 

 the stream beyond the union of the Middle and Salt forks. 



Epiiemerid,\ 



Most species of May-flies are markedly intolerant of pollution. In 

 the present survey, one species (CalUhaetis) was constantly found in con- 

 taminated waters, or even, in one case, in waters that might be considered 

 as polluted. All other members of the family Ephemeridae found, were 

 distinctly clean-water species, these belonging to the genera Hcxagcnia, 

 Ephemera, Polymitarcy's, Heptagcnia, Bactis, Cliirotciietcs, Caciiis, Calli- 

 bactis, and Ephemcrella. 



Odonata 



Naiades of Anax Junius and Lihellula pulchella were taken at Station 

 13 under conditions indicating pollution. The latter species has been 

 taken in the Boneyard stream by students in the Department of Zoology 

 at the University of Illinois and must be considered as being the 

 most tolerant species encountered on this survey. Species of the genera 

 Goiiiphus and Synipctrum were found in the stream at the Shakerack 

 bridge (Stations 15 and "?6) under conditions indicating contamination. 

 All of the above are water-breathing forms. No naiades of the suborder 

 Zygoptera were to be found in the stream except in clean water but there 

 they occurred in great abundance. The Odonate fauna of the unpolluted 

 portions of the Salt Fork belong to the genera Goinplins, OphiogomphuS, 

 Epiacschna, Macromia, Hetacrina. Enallagma, and Ischiuira. In addition 

 to these naiades, adult dragon-flies were observed ovipositing in the 

 stream. These included Lihellula pulchella and Platheiiiis lydia at Station 

 12, where the stream was strongly polluted, but it can not be stated that 

 the naiades mature in polluted or septic streams. The fact that these in- 

 sects oviposit in places where there is no chance of the continuance of the 

 species is well known, as in temporary puddles over concrete pavement. 

 In clean parts of the Salt Fork other adult dragon-flies seen ovipositing 

 in the stream included such species as Hetaeriiia ainericaiia, Argia mocsta 

 putrida, and Ischnura z'crticalis. 



Hemii'tera 



A water-strider, Gcrris mnrginatus, wqs obsers'ed at Station 4 where 

 conditions were unquestionably septic. As the insect is an air-breather 

 its occurrance here has no significance. At Station 10, where the water 

 was considered to be polluted, the following groups of water-bugs were 

 found: Corixidae, Belostomidae (Belostoiiia tlumi)icum, including 



