36 
Transactions of the Academy of Science of Si. Louis 
June and July. It is realized that light trap collections may not 
give an exact indication of the relative numerical abundance of 
each species caught, for species differ in their attraction to light. 
However, hand catches are a no more reliable indication of 
actual abundance, for species differ greatly in their attraction 
to man. The following table (Table 3) gives the results of hand 
catches and light trap catches. 
t 
Further interesting information was found when the light 
trap catches were divided into periods during the night. The 
campus trap ran almost every night during June, July, August 
and September from 7:00 P. M. until 8:00 A. M. During a con- 
siderable part of this time the collecting jar was changed at 11 :00 
P. M., so that the collection was divided into two periods, the 
first covering four hours and the second, nine hours (Table 4). 
From these data it has been shown that per four hour period 
there w^as a significantly greater number of mosquitoes caught 
during the second period of the night than during the early part. 
It has also been shown that the sex ratio during the early part of 
the evening does not deviate significantly from equality, but that 
there is a significantly greater number of females during the 
second period. 
4) Habits of Mosquitoes. In instituting control measures 
it is essential to have knowledge of the biting and other habits of 
the various species. Much information of this kind already ex- 
Table 4 
Light Trap Records 
Mosquitoes of St. Louis County 
1942 
7 P.M. 
Males 
June 17 
July 
72 
Total 89 
11 P.M. 
Females Totals 
19 
75 
94 
36 
147 
183 
11 P.M. — 8 A.M. Catch 
Males Females Totals Total 
49 
202 
251 
125 
544 
669 
174 
746 
920 
210 
893 
1103 
