Temperal Dissociation and Population Regulation in Certain Hesperiine Butterflies

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Abstract
Eleven species of flower feeding hesperiine butterflies are open field residents in a locality in western Pennsylvania. They may be grouped in 5 sets. The species of each of the first 4 sets (respectively 3, 2, 2, 2 species) are remarkably precise chronological replacements in the timing of their average adult flight periods (the basis for the set groupings). The times of the population peaks of set II, furthermore, coincide with population minima of set 1 (the numerically dominant set). Aggregate Daily Nutrient Demand (DND–the product of average body volume and estimated average population density of a species on a given day) of these species reaches 4 peaks through the annual season, and these peaks coincide approximately in time with the peaks of aggregate DND of all other butterflies in the area and with the local flowering times of the major adult food flower species. (The fifth set, of two species, is quite rare and replacement timing is imperfect, possibly related to the extreme mimetic resemblance of the two.) It is argued that these temporal dissociations arose adaptively to reduce or eliminate competition for adult food (flower nectar), and that the availability of adult food is therefore a population regulator of these butterflies.

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