Sample Data

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

A fertilized female bean beetle was permitted to lay eggs on ten bean species, not including the natal bean species. The natal bean was mung (Phaseolus aureus) in this experiment. A total of 17 independent trials were conducted, each with one female. In each trial, 10 beans of each of the following were presented to a female: black-eyed peas (BEP, cowpea) (Vigna unguiculata), garbanzo (Cicer arietinum), kidney, pinto, navy, and black beans (Phaseolus vulgaris), soy beans (Glycine max), adzuki beans (Phaseolus angularis), lima beans (sieva bean) (Phaseolus lunatus), and green pea (Pisum sativum). Females were permitted to lay eggs for 96 hours before they were removed and the eggs were counted. The difference between bean types in the mean number of eggs laid per female was highly significant (ANOVA, F_9,160=15.1, p<0.0001, Figure 1). An alternative statistical analysis could be based on the frequencies of eggs (the total eggs counts) on each bean type (a chi-squared test). That analysis also indicated a highly significant difference between bean types in the number of eggs laid (X²=717.9, df=9, p<0.0001).

Figure 1. Number of eggs laid per female. The mean ± SE of eggs laid per female on each of 10 bean types is shown for the 17 independent trials conducted with females from mung beans. Each of the 17 replicates contained 10 beans of each of the 10 types, so these means are based on 170 beans of each type. The value shown at the top of each bar is the total number of eggs laid on each bean type.

The elapsed time from egg laying to the emergence of an adult (development time) and the mass of the newly emerged adult beetle was evaluated for each bean species on which eggs were laid. Beans with eggs were followed for a total of 40 days after egg laying to permit adequate time for adults to emerge. Adults only successfully emerged from adzuki beans and black-eyed peas (BEP) and the development time from black-eyed peas was significantly faster than from adzuki beans (ANOVA F_1,23=24.4, p<0.0001, Figure 2). There were no significant differences between the sexes in development time emerging from a given bean species (ANOVA F_1,23=0.5, p=0.49, Figure 2). The mass of newly emerged males and females was significantly greater for adults emerging from black-eyed peas compared to adzuki beans (ANOVA F_1,15=4.7, p<0.05, Figure 3). Females had significantly greater mass at emergence than males (ANOVA F_1,15=6.1, p<0.03, Figure 3).

Figure 2. Development time of bean beetles emerging from adzuki beans and black-eyed peas (BEP). The mean ± SE development time (egg laying to emergence of adult) is shown for males and females emerging from the two bean species from which adults successfully emerged. Sample sizes are shown at the top of each bar.

Figure 3. Body mass of bean beetles emerging from adzuki beans and black-eyed peas (BEP). The mean ± SE mass at emergence is shown for males and females emerging from the two bean species from which adults successfully emerged. Sample sizes are shown at the top of each bar.