70 ROBERT STANLEY McEWEN 
ward the light both by crawling and flying, whereas the latter 
can only crawl. When not agitated, however, the response even 
of winged insects is almost purely a crawling reaction. 
Three groups of flies containing 20 insects each were now se- 
lected at random from the stock bottles. They were placed in 
vials in the morning and tested according to the above plan in 
the afternoon. After this first test all the insects were etherized 
and the wings removed from the two groups which had made 
the best record. These groups will be designated as B and C. 
The following afternoon all three groups were tested again. 
Following are the records of Groups B and C before and after 
the wings were removed, and also the two records of the control 
Group A (table 9). 
TABLE 9 
Before removal. Temperature 24° 
A B Cc 
Gravity , Light Gravity Light Gravity Light 
(First test) 
Males Males Males Males Males Males 
29.1 57.6 28.3 75.0 MN 65.0 
Females Females Females Females Females Females 
31.6 81.6 45.0 90.8 a1) 5 85.0 
After removal 
‘(Second test) 
Males Males Males Males Males Males 
50.0 86.6 35.0 5.8 39.1 20.8 
Females Females Females Females Females Females 
41.6 90.8 30.0 Ud) PASO) By lh 
As a further. check, Group A, the control, was tested a third 
time 48 hours after the second test. The wings were then re- 
moved and eight hours later a fourth test was given (table 10). 
It is evident from this data that the removal of the wings affects 
the light reaction specifically, and does not merely reduce the 
activity of the insects. 
The next point investigated was the effect of the removal of 
parts of these appendages. The first experiment was done un- 
