HOW TO MAKE REGIONAL LISTS OF BUTTERFLIES - Yale University

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VOLUME 33, NUMBER 422980Se =78 species7019611964•196319621965 19681966 1967U)60c)1958a:2 50w •.~0wU) 40'"~W.Q!3z 30'"""" "0E-
230 JOURNAL <strong>OF</strong> THE LEPIDOPTERISTS' SOCIETYsumably because of variation in weather conditions. It takes severalyears of observation to establish reliable average times.One of the reasons for a diversity of flight periods among the speciesof a community is to minimize competition for adult food-normallyflower nectar-and a thoughtful examination of your data in this lightcould produce interesting results.Population levels. Each species has an average level of abundance:some are rare, others commoner, and some are abundant. In any givenarea the frequency distribution of species according to abundance isclose to log-normal, that is, the frequency distribution approximatesa normal curve when abundance is plotted on a logarithmic scale.Since the abundance scale ("0-8") described above is logarithmic, afrequency distribution of the species based on their average abundanceaccording to that scale should approximate a normal curve. Thecurve is truncated at the rare end, but the degree of truncation diminisheswith prolonged study. Most species vary considerably intheir numbers from year to year, and again it takes a number of yearsof observation to establish reliable average values. Some species mayhave different abundance levels in different broods, and this variation,too, should be looked for.Cycles of commonness and rarity are often present, but beware ofgeneralizing too much from them. Many cycles are transient, or nottruly cycles (having varying periods).True regular cycles are uncommon. Eventually you should find insome species a "boom and bust" phenomenon. This is a season (orflight) of exceptionally high numbers, followed by a crash, duringwhich you will see only a few individuals, or even none at all. A returnto normal numbers soon follows. At Powdermill I have seen this ina few species (Euphydryas phaeton, Polygonia comma, Epargyreusclams, Hesperia leonardus) oVer about 16 years of observation. In eachof these only one eruption was seen, ordinarily about 2 abundanceunits above normal, followed by a crash of similar magnitude, with areturn to normal numbers the year after.Habitat choices. With appropriate observation and recording, theprincipal habitat and subordinate habitats of most of the speciesshould be learned in comparatively few years. Watch for species thatregularly occupy two or more different habitats, especially (a) for feeding,and (b) for courtship, reproduction, larval growth, and inactive("sleeping") adult occupancy.Territorialism. Many butterfly species are territorial. The subjecthas scarcely been touched, and much remains to be learned. Persistentobservation should reveal territorial individuals if you are alertto what the butterflies are doing. Absence of territorialism in a species
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HOW TO MAKE REGIONAL LISTS OF BUTTERFLIES - Yale University

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