Phenotypic variation is determined by both additive genetic variation and an organism’s environment. Many studies have measured patterns of selection acting on phenotypes where the majority of variation is the result of additive genetic variance. Fewer, however, have measured patterns of selection acting on traits where the majority of phenotypic variation is determined by the environment. In this study, we measured several factors that contribute to the expression of environmentally-determined phenotypically plastic structures and compared them across species, populations and structures to better understand the ways in which common, highly plastic structures respond to selection. We provide data for two emerging model systems– the red-winged soapberry bug Jadera haematoloma and the broad-horned flour beetle Gnathocerus cornutus. Both organisms have highly plastic traits where the majority of phenotypic variation is determined by the organism’s developmental environment. J. haematoloma displays a wing polyphenism where the size and shape of wings are dependent on the type and quality of the organism’s host plant. G. cornutus bears highly plastic sexually selected mandible weapons where weapon size is determined by the nutritional environment during critical points in development. We measured traits that were environmentally regulated (mandibles/wings) as well as traits that exhibit more patterns in development (eyes/beak). Overall, our results provide critical insight into how highly plastic environmentally regulated structures and structures with relatively low heritability evolve ultimately contributing to holistic comprehension of morphological diversity and evolution in general.