I studied the sex-limited red spots on the wings of male rubyspot damselflies (Hetaerina americana) in relation to territoriality and fitness in the wild. Both observational and experimental (wing spot manipulation) studies indicated that wing spots were selected through competition among males for mating territories, not through female choice or direct competition for females. Males with naturally or artificially large wing spots were more successful at holding territories and consequently mated at higher rates than males with relatively small wing spots. In contrast, sexual selection on male body size appeared to operate among nonterritorial males at the clasping stage of the mating sequence, perhaps because larger males were better at clasping females forcibly. Of four models proposed to explain the evolution of ornaments through territory competition, only the agonistic handicap model makes predictions consistent with the results of this study.

Evolution by natural selection is key to understanding life and of considerable practical importance in public health, medicine, biotechnology, and agriculture. The Next Generation Science Standards (NGSS) include natural selection among several evolutionary concepts that all third-graders should know. This article explores a novel approach to developing and testing curricula for teaching natural selection and related concepts to children. College students developed lesson plans with specific evolutionary learning objectives based on the NGSS and taught them at elementary schools. Learning was assessed with a pre/post-test design, and a subset of students was retested after two years. After just two hours of instruction and active-learning activities, students of all three grade levels tested (grades 3–5) demonstrated substantial improvement in their understanding of evolutionary concepts. Students who were retested in grade 5 scored higher than fifth-graders who had not participated previously. The most challenging concepts for all grade levels were common ancestry and natural selection, but fifth-graders showed more improvement than third- and fourth-graders. If this finding is substantiated by further research, an adjustment to the NGSS schedule might be warranted. Spacing evolutionary biology concepts out might be a better strategy than concentrating them all in grade 3.

Ornaments could evolve as honest indicators of fighting ability, provided they have costs that make deceptive signalling unprofitable. I tested for such costs by manipulating the size of the intrasexually selected wing spots of male rubyspot damselflies (Hetaerina americana) and monitoring survival in the field. Males with enlarged spots had higher mortality rates than both unmanipulated and sham-manipulated controls. Natural wing spot size correlated positively with longevity, which suggests that higher quality males develop larger spots.

I review methodological problems that can lead to false evidence for selection on secondary sexual characters and present a study of selection in rubyspot damselflies (Hetaerina americana) that avoids these pitfalls. Male rubyspots have a large red spot on each wing that grows to a terminal size after sexual maturity. Selection gradient analyses revealed evidence for positive sexual and survival selection on both terminal wing spot size and body size. Phenotype manipulations confirmed that wing spot size was subject to direct sexual selection, but showed that the positive slope of survival on wing spot size was an indirect effect of selection on unmeasured traits. This study provides the strongest evidence yet for sexual selection on coloration in Odonata, but also provides clear examples of why phenotypic selection statistics must be calculated and interpreted cautiously.