Intraspecific body size variation in Macrolepidoptera as related to altitude of capture site and seasonal generation

"As a proxy for body size, forewing lengths of individual geometrids and noctuids were measured with respect to altitude of capture site in five species in North Carolina and one in Costa Rica. Number of specimens ranged 48–373 per species, number of capture sites 2–15 per species, and site altitudes ranged 2–2209 m. Forewing length in all six species increased significantly with increasing altitude at rates of ≈ 0.3–≈ 1.1 mm/500 m. These relations held where investigated for both first and second annual generations and for both sexes even though second-generation individuals were smaller-bodied. Thus examples of Geometridae and Noctuidae are added to a list mainly of micromoths previously known to exhibit positive size–altitude relations. Some adaptive and nonadaptive body-size hypotheses are discussed as possible explanatory factors, but thus far no explanation is fully satisfactory. In contrast to measurement results in these six macromoths, other moths known to be widely dispersive appeared to display flat size–altitude relations, and published butterfly size–altitude data varied irregularly. Degree of dispersiveness is hypothesized as a condition to the manifestation of size–altitude phenomena in lepidopterans. Many more minimally dispersive moths will likely be found to increase in body size with increasing altitude."