Sample Data

The results reported below were collected William D. Shipman III, a Morehouse College undergraduate.

A fertilized female was permitted to choose between laying eggs on mung beans or adzuki beans in this experiment.  A total of 14 independent trials were conducted in which 10 beans of each species were presented to a different female that had emerged from mung beans.  Females were allowed 96 hours to lay eggs before being removed.  The mean number of eggs laid per female on adzuki beans was significantly greater than on mung beans (paired t-test, t=2.602, df=13, p=0.02, Figure 1).  An alternative statistical analysis could be based on the frequencies of eggs (the total eggs counts) on each bean species.  That analysis also indicated a highly significant difference between bean species in the number of eggs laid (binomial test, p<0.001).

Figure 1. Number of eggs laid per female.  The mean ± SE of eggs per female laid on either adzuki or mung beans is shown for the 14 independent trials conducted with females from mung beans.  Each of the 14 replicates contained 10 beans each of these two species, so these means are based on 140 beans of each species.  The value shown at the top of each bar is the total number of eggs laid on each bean species.

The elapsed time from egg laying to the emergence of an adult (development time) and the mass of the newly emerged adult beetle also was evaluated for the two bean species in this experiment.  Beans with eggs were followed for a total of 40 days after egg laying to permit adequate time for adults to emerge.  The development time from mung beans was significantly faster than from adzuki beans (ANOVA F[1,73]=116.9, p<0.0001, Figure 2).  There were no significant differences between the sexes emerging from a given bean species.  The mass of newly emerged males and females was significantly greater for those adults emerging from mung beans compared to adzuki beans (ANOVA F1,73=9.9, p=0.002, Figure 3).  Females had significantly greater mass than did males (ANOVA F[1,73]=22.3, p<0.0001) and there was a significant interaction between bean and sex on emergence mass (ANOVA F[1,73]=5.7, p=0.02, Figure 3).  Although the number of eggs on, and therefore larvae in, a given bean can influence development time and adult mass at emergence, there were no consistent significant relationships between either development time or mass and the number of eggs laid on a given bean for either males or females.  This suggests that these results are not confounded by competition between larvae in beans that received more than one egg.

Figure 2. Development time of bean beetles emerging from adzuki and mung beans.  The mean ± SE development time (egg laying to emergence of adult) is shown for males and females emerging from these two bean species.  Sample sizes are shown at the top of each bar.

Figure 3.  Body mass of bean beetles emerging from adzuki and mung beans.  The mean ± SE mass at emergence is shown for males and females emerging from these two bean species.  Sample sizes are shown at the top of each bar.