458 



Almost the same statements apply to the Haliplidae, two species of Pclto- 

 dytes being very numerous in the stream between St. Joseph and Sidney 

 under conditions that were strongly contaminate. Dytiscidae, the 

 predaceous water-beetles, were about equally common in contaminated 

 portions of the stream and at the critical station (■■!.j and 10) near the 

 bridge at Sidney where clean water conditions obtain for the first time. 

 The Parnid beetles (Dryopoidea) included adults of a species of Stcncl- 

 mis under pollutional conditions at Station 10. The majority of the mem- 

 bers of this group appeared only in the cleaner water situations, however, 

 as shown by the large numbers of specimens of Hclichus lithophihts. 

 Hclmis vittata, and species of Stcnehnxs taken, the last-named being found 

 both in the larval and adult stages. Although careful search was made for 

 them, no specimens of the water-penny, Pscphciius hcrricki (DeKay), 

 were noted.* It may be that the range of the species is more northerly 

 than the latitude of the Salt Fork. Members of the famil)' Dascyllidae 

 were noted commonly along the stream margins and among the beds of 

 Dianthera in clean water conditions. The larval stage was the only one 

 noted, and these may belong either to the genus Cyphon or to Scirtes. 



* The writer can see no just reason for ignoring DeKay's name. Fhtvicola herrlcki. 

 applied to the larva of tliis species, under the misconce'ption of its being an isopod 

 crustacean, six years before the adult beetle was named Psephenus lecontei by Le- 

 conte. The generic name Fluvicola is preoccupied in Aves (Swainson 1S27) and so 

 can be dropped from consideration. However, there seems to be no reason for ignor- 

 ing DeKay's specific name based on the immature stages. Similarly DeKay's Fhtvi- 

 cola tnberculata is very pr'obably the larva of Hclichus lithophilits. An entirely com- 

 parable case is found in the May-fly Prosopistovia foliacenm- Foiirc. in Europe, and 

 in this instance the use of this name has never been questioned. The insect was de- 

 scribed in 1764 by Geoffrey as a crustaceous form and re-named by pourcroy in 1785 

 as a species of Crustacea. It was fully a century after its original discovery that the 

 true i-elationship of this remarkable insect was made known. 



DiPTERA 



Together with the tubificid worms, members of the dipterous families 

 Psychodidae, Chironomidae, and -Syrphidae are considered as among 

 the best indicators of septic or pollutional conditions. The larvae of the 

 Psychodidae and Syrphidae are air-breathers, obtaining their supplv of 

 oxygen directly from the atmosphere through Ijrea thing-tubes, verv short 

 in the former case, extremely long and extensile in the case of the rat- 

 tailed maggots {Erisfalls and Hdophilits). No members of these septic 

 groups were encountered in the 1921 survey. The great family of midges, 

 Chironomidae, includes a range of species from forms which can 

 stand pollution (such as Tanypus iiwnilis. L., Chironomus plinuosiis L., 

 C. maturus Job., and C. frcqucns Joh.) ; and less tolerant forms (such as 

 Cluronoiiiits crassicaudatiis Mall., C. decerns Joh., C. glohifcnis Say, 

 C. z'iridicollis v. d. W., Tanypus dyari Coq.) to others which appear to 

 be strictly clean-water species and unable at all to stand pollutional con- 

 ditions (such as Cliironomus nigricans Joh., C. fcrrugincoi'ittatns Zett., 

 and Procladius concinnus Coq.). For a detailed consideration of these 

 species the reader is referred to the paper by Richardson (inSla, page 

 72 and table). 



