Juday—Quantitative Studies of Fauna in Lake Mendota . 473 
the months of October and November. In December, 1916, the 
number was the same as in the previous month, but there was a 
slight decline during the next two months with a distinct rise in 
March to the largest average number obtained in the entire series 
of observations. This maximum was followed by a uniform de¬ 
crease to the August minimum of 1917. 
Fig. 1. The curves in this figure show the average number of larvae 
of Corethra punctipennis in thousands per square meter of bottom for the 
different months during the period of these observations. The vertical 
spaces range from zero to 30,000. The curve shown as a solid line repre¬ 
sents the averages for station II; the broken line indicates the monthly 
averages for the five stations in deep water combined. The latter curve 
is interrupted during the winter because observations were not made 
regularly at all of these stations during this season. (See table 11.) 
This summer minimum was succeeded by an autumnal rise which 
culminated in a December maximum, but the December maximum 
of 1917 was appreciably smaller than that of December, 1916. No 
samples were obtained at station II in January, 1918, but from 
February to May there was a gradual decline in the number of 
larvae obtained at this station, followed by a rapid decrease during 
the next three months to the August minimum of 1918. The larg¬ 
est number of larvae obtained in any of the samples was 33,800 
individuals per square meter, this number being found at station 
