Table 1.

Influence of dislodgement or retention of the first male’s mating plug on the relative number of sperm from competing males that reach the uterus

Factor	12	P
No. of second male’s sperm
Retention of first male’s mating plug	5.42	0.02*
Total sperm no. in uterus after double mating	8.55	<0.01**

When two males mated with the same female, the relative number of their sperm varied significantly according to whether or not the first male’s mating plug was retained. The data are presented in Fig. 3A. Relatively fewer sperm from the second male were present in the uterus when the first male’s plug was retained. Results are shown for linear mixed models fit by maximum likelihood, testing the effect of plug dislodgement or retention on the number of sperm recovered from the second male for 16 double copulations in which sperm were recovered from both males, consisting of 16 males in role 2 (mating second) and 10 in role 1 (mating first). This excludes one case in which no sperm from the first male were recovered although this doesn’t significantly alter the outcome of the analysis. The identity of the first male to mate is included as a random factor. Bold text indicates statistical significance (*P < 0.05; **P < 0.01). χ² = Chi-squared.