REACTIONS TO LIGHT AND GRAVITY IN DROSOPHILA 65 
TABLE 6 
MALE | FEMALE 
TENTED: UIVESSH pene eI Sa aRE aa eae he e aiea Simei tec a) Bie an ae 71.8 97.8 
SGT | ETS yee ener ern aha MLC URN NMP iia te A pane bg a. ee Comte eo 90.0 100.0 
IM vitiexa | HeYEA et ae aS COG A Aa ae Pe eer as Gee AU rae 93.1 97.8 
included in this average this statement would no longer hold. 
The indices for these insects were as follows (table 6): The 
average male index is 84.9 and the female, 98.5, with a difference 
of 13.6. Thus while the males have again gained relatively, the 
females are also absolutely much faster than are younger females. 
Finally, a series of tests were run on flies 4 to 6 days old as fol- 
lows. An initial test was run at the same time of day at which 
it had been the custom to remove newly hatched flies from their 
bottles. They were then tested at the same relative intervals 
as the newly hatched insects had been in the experiments de- 
scribed above. In this case ten males and ten females were 
used in each group, and the number of trials constituting a test 
was raised to 5. The results were as follows (table 7): 
TABLE 7 
Male indices 
0 HRS. 4 HRs. 12 HRS. 15 HRs. 18 HRs. 21 HRS. 24 HRs. 
83.6 86.5 88.5 86.6 86.8 96.6 98.8 
Female indices 
96.8 98.3 | 97.6 Sigel 96.8 96.1 | 99.0 
Temperatures 
| | 
22° oe | Ie alae 2 | Pale 2G. 22 
The main feature of this series is that there is no drop occur- 
ring in the middle of the series, such as was the case with the 
young flies tested at similar intervals. It is thus made more 
likely that the falling off in question was due, as suggested, to 
the more rapid fatigue of newly hatched insects. Incidentally, 
it will be noted that the males are not far behind the females, 
and that they gain on them during the series. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, NO. 1 
