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Clones of the broad—leaved cattail (Typha latifolia L.) and soil samples were obtained from near a zinc smelter and from a control location. In the smelter location, soil zinc concentration was 385 times higher, cadmium content 37 times higher, and lead content 16 times higher. No evidence for the evolution of heavy metal tolerance could be detected in 2 x 2 experiments in which genotypes from both locations were grown on both soils. Growth of genotypes from both locations was inhibited on the heavy metal soil, but not to the extent that would be expected from previous studies of heavy metal effects. This is the first case described in which a species has been able to colonize heavy metal soils in the absence of the evolution of tolerant races.

The larval head widths at each instar, life cycles, and food habits of late instars were determined for five species of Rhyacophila from two Appalachian mountain streams in South Carolina, U.S.A. Rhyacophila acutiloba Morse & Ross was univoltine with two cohorts, one emerging in the spring and another presumably emerging in early autumn. Rhyacophila fuscula (Walker), R. nigrita Banks, and R. Carolina Banks were apparently multicohort, univoltine species with extended flight periods. Rhyacophila minor Banks was univoltine with a spring emergence. All species were predaceous and consumed mainly Plecoptera nymphs and Trichoptera larvae.

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The triclad flatworm Dugesia tigrina (Girard) is abundant in Lake Wabamum, a west—central Alberta lake receiving thermal effluent. A 14—month study was carried out to investigate D. tigrina's population ecology and the effect a thermally altered environment might have on Dugesia. Our data support the hypothesis that D. tigrina is limited by intraspecific competition for food during and after reproduction. In spring, both the normal water and heated water triclad populations grew rapidly and produced cocoons. Recruitment of young intensified food competition, causing shrinkage and mortality. The spring gain in length and weight was lost through shrinkage of individuals, and numbers of triclads in autumn were similar to prebreeding numbers. Hence the hypothesis is supported for populations in the thermally altered and the normal lake habitats. Triclads from the thermally enriched environment were found to be 2x as fecund as normal lake triclads. Cocoon production was probably increased to some extent by thermal effluent. However, the elevated mortality rate caused by the mechanical harvesting of abundant macrophyte populations in the warm water area, estimated at 1—3x the standing crop of triclads, probably accounts for much of the increased fecundity.