88 NINETEENTH REPORT STATE ENTOMOLOGIST OF MIN NESOTA—1922 
in glass jars, one lot in which the humidity was kept near the satura- 
tion point by supplying fresh potato leaves regularly. These created 
enough moisture to condense on the sides of the glass. The other 
lot of jars contained only cheese-cloth for the bugs to crawl over and 
thus was kept at the same humidity as the outside air. The bugs used 
in these experiments were in each case selected from one egg mass, 
part placed in the humid jars and part in the low humidity jars. 
Both lots of jars, when kept at a temperature of 85°F. or higher, 
matured a high percentage of white color forms, an occasional yellow 
male, but never a red one. The results from these two extremes indi- 
cate that humidity has little, if any, influence on the coloration of 
the bugs. These experiments were carried on during two different 
years but always with similar results. 
Sunlight can scarcely be said to have a direct influence on the color 
pattern, for the above experiments have been carried out in the labora- 
tory where the bugs were never exposed to direct rays of the sun, 
However, if the deposit of pigment granules in the hypodermis has 
a direct relation to physiological processes in the bug, it- is very prob- 
able that sunshine indirectly speeds up these processes. Many observa- 
tions show that sunshine stimulates an insect to greater activity, as 
do high temperatures even without sunshine. But at a given tem- 
perature, sunlight probably speeds up the physiological processes and 
produces what otherwise would be attained only at a higher temperature 
in the absence of the sun’s rays. 
Relation of Color to Sex 
It was observed rather early in these studies that the male sex 
averaged darker in color than the female, altho it is possible to find 
white males as well as red females. An average population of 341 
bugs, collected during August and September, 1913, gives the follow- 
ing results: 
White form Yellow form Red form 
163 852 LOnS= 502 [2S eo aigas 
From this it 1s observed that in a given population of bugs, reared 
under the same average conditions, the male sex tends to be dark 
in color while the females tend to be light. This difference in color 
may very well be accounted for on a physiological basis. Since the 
females must mature large numbers of eggs it seems reasonable to 
suppose that the physiological processes go on at a higher rate than 
is the case in the male. Male specimens of the white color form have 
never been reared except with temperatures averaging above 82°F. 
