BEHAVIOR. 11 
DURATION OF COPULATION NECESSARY. 
As shown above, the length of time pairs remain mated is charac- 
teristic for each species, ranging from about a minute in Drosophila 
lutzit to about an hour in D. immigrans. The usual time for D. 
melanogaster is about 21 minutes. I have conducted a few experiments 
with this species, to see how long a time is necessary. Nine pairs 
were mated, in each case using a male with a dominant mutant char- 
acter, so that any offspring produced could be identified as his and 
not due to a previous mating. These pairs were allowed to mate, 
and were then shaken apart after a few minutes. The females were 
then isolated to see if they would produce offspring. In no case was a 
complete count of the offspring made, so that the figures given in 
table 1 represent only minimum numbers. Evidently 8 minutes is 
about the time required. 
TABLE 1. 



Mime in minutes; pair was mated...) .)..oe. i. 2. ke 
Nim ber, Of Spring PrOGUCEG ..).2 245 eg a 
