The composition of benthos in a series of 29 lake and peat pool sites is examined especially in relation to a successional gradient . The results indicate a sharp distinction between the fauna of peat pools and lakes . Chironomus, Psectrocladius, Monopsectrocladius, and Zalutschia are characteristic of bog lakes at the latter stages of their evolution and peat pools . Procladius and Tanytarsus dominate in most lakes . Between weakly acidic and strongly acidic lakes a sharp boundary exists for many other components of the benthos .Chaoborus occurs in strongly acidic lakes . Amphipoda, and Ephemeroptera are limited to weakly acidic or circum-neutral waters .A comparison of the results of this investigation with a parallel paleoecological study is made .

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A comparison of the present chironomid fauna of four shallow, humic lakes with the subfossils of surficial sediments is made . The chemistry and benthos of the lakes investigated varied greatly . Results indicate a reasonable correlation between biocenoses and thanatocenoses, but a marked under-representation of Procladius is apparent . It is suggested that, at least in shallow, humic lakes, Procladius be excluded in attempts to reconstruct chironomid communities from subfossils .

The efficiency of recovering subfossil chironomid head capsules from lake sediments was investigated using a variety of methods. Preparation of the sediment by boiling in 10% KOH and washing in a 37 pm sieve, as compared to unprepared sediment, did not affect the number of head capsules recovered per volume of sediment. Sieves having meshes greater than 100 I.rrn lose many of the smaller head capsules.

Reproducible live wet weights may be obtained for medium to large larvae of Metriocnemus knabi and Chironomus attenuatus after blotting them on filter paper for 1 min. To obtain reliable measures of wet weight for smaller larvae the blotting time must be reduced in proportion to the surface area/volume ratio of the larvae. Dry weights are easily obtained by oven drying at 60 °C for 24 h but drying for several days does not affect the results. A temperature of 100 °C decreases die percentage dry matter in C. attenuatus. Both species display an increase in percentage dry matter with increasing size. The extent to which the gut is filled with food has no effect on the percentage dry matter. Attempts to determine dry weight directly from preserved larvae were unsuccessful.