484 Wisconsin Academy of Sciences, Arts, and Letters. 
Baker (1) states that the larvae of Sialis infumata were rare in 
Oneida Lake and that they were found only where the water was 
between 2.5 feet and 8.5 feet deep. In Lake Mendota they were 
found regularly at a distinctly greater depth, that is, from 5 meters 
to 20 meters. 
Table 17 shows the live weight and the dry weight of those forms 
inhabiting the intermediate zone for which gravimetric data have 
been obtained. Such determinations have not been made for the 
leeches, snails, Hyalella, Palpomyia, and Chironomus lobiferous, 
but these forms were found in such small numbers that the addi¬ 
tion of their weight to the data given in this table would not in¬ 
crease the general average for the whole zone very materially. 
These weights are based upon the numerical results obtained for 
the intermediate depths and upon the mean weights of the various 
forms. The data given in this table should be compared with those 
given for the deep-water area in table 15. 
As might be expected from the numerical results, the Oligochaeta, 
Pisidium, and Corethra yield a smaller quantity of dry material 
in the intermediate than in the deep-water zone. On the other 
hand, Chironomus and Protenthes show a larger amount in the 
former than in the latter. Chironomus tentans yielded nearly 
twice as much dry material in the intermediate area as it did in 
the deep-water region, while Protenthes was about one-third 
greater in the former zone. The dry weight of the Oligochaeta 
was a little more than twice as large in the deep-water zone as in 
the intermediate zone; Pisidium gave somewhat less than twice as 
much in the latter region and Corethra substantially three times 
as much. 
With respect to the larvae of Sialis infumata, it may be said that 
the weight of the different sizes of individuals found in the samples 
was not determined, but gravimetric data were obtained for the 
full-grown larvae when they migrated to the shore for the purpose 
of pupating. About 4,500 individuals of this size were secured for 
a chemical analysis, and the dry weight per individual for this 
number was 8.4 milligrams. Thus an average of 10 larvae per 
square meter in the intermediate zone, on the basis of full grown 
larvae, would mean 0.8 kilogram per hectare, or about three quar¬ 
ters of a pound per acre. The mixed sizes found in the samples 
would yield a smaller quantity of dry matter, however, probably 
not more than half a kilogram per hectare, but the maximum 
amount has been indicated in the table. 
