Natural selection increases female fitness by reversing the exaggeration of a male sexually selected trait.

Theory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to our knowledge, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we use experimental evolution of replicate populations of broad-horned flour beetles to test for effects of sex-specific predation on an exaggerated sexually selected male trait (the mandibles), while also testing for effects on female lifetime reproductive success. We find that populations subjected to male-specific predation evolve smaller sexually selected mandibles and this indirectly increases female fitness, seemingly through intersexual genetic correlations we document. Predation solely on females has no effects. Our findings support fundamental theory, but also reveal unforseen outcomes-the indirect effect on females-when natural selection targets sex-limited sexually selected characters.

Release of the Flightless Strain of Harmonia axyridis (Coleoptera: Coccinellidae) Against Two Aphid Species on Komatsuna (Brassica rapa var. perviridis) in Open Fields.

Myzus persicae (Sulzer) (Hemiptera: Aphididae) and Lipaphis erysimi (Kaltenbach) are important pests of Brassica leafy vegetables, especially in Japan, the United States, and India. In Japan, because most of the nonheading Brassica vegetables are considered minor crops, the number of commercially available pesticides against these aphids is limited. Here, we evaluated the effect of releasing adults of a flightless strain of the multicolored Asian ladybird, Harmonia axyridis Pallas, on these aphid species on a nonheading Brassica cultivar in open fields. Three weeks after, ladybirds were released onto aphid-infested plants at a rate of two adults per m2, only 4-12% equal numbers of aphids were found on plants with ladybirds as without ladybirds in all three trials. The result indicates that H. axyridis adults are the effective biocontrol agents against aphids on the plants.

Walking activity of flightless Harmonia axyridis (Coleoptera: Coccinellidae) as a biological control agent.

The use of flightless strains of the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), established via artificial selection, can be highly effective as a biological control agent for aphids. However, flightless H. axyridis must depend on walking for dispersion. Therefore, data on the walking activity levels in flightless strains are important for the development of effective methods when releasing these agents in the field. Results of measurement of walking activity levels using an infrared actograph showed that walking activity levels during the daytime (but not nighttime) in both sexes of pure flightless strains tended to be lower than those of control strains. We also found that walking activity levels during the daytime for the F1 generation of hybrid strains, produced by reciprocal crossing between two pure flightless strains, were approximately equal to those of pure strains; the reduction in walking activity levels was not recovered by hybrid vigor. Our results indicate that the reduction in walking activity levels in the pure flightless strains was not caused merely by inbreeding depression stemming from the artificial selection process. Instead, potentially flight ability and walking activity levels in this species may be controlled by the pleiotropic effect of a gene.