Patterns of Geographic Variation in Adult Flight Phenology of Some Nearctic Trichoptera

Summary

Analyses of published records of adult capture periods of some nearctic Trichoptera reveal significant linear regressions against latitude for many species. For most species first date of capture was later with increasing latitude. Furthermore, length of capture period for a given taxon decreased with increasing latitude. For autumn-emerging species these patterns are reversed, with date of first capture earlier, and capture period longer with increasing latitude. The slopes of these relationships depend on how early (or late) in the season a species emerges as adults. The linearity, absence of discontinuities, and the large amount of variance explained by latitude suggest reduced developmental synchrony within a cohort and/or a continuous trend to multiple, overlapping cohorts with decreasing latitude.