Affect of Cold, Wet Summer on Monarch Populations Observations by Gary Hughs, Palmyra, NY Since we started raising monarchs, which I think was 1991, we have had two years of cold and wet summers, by which I mean colder temperatures and more rain than we normally get around here. The first year was 1992, known in this area as the "year without summer;" this year is the second. Perhaps saying that we "always" see this phenomena in non-normal summers is a bit strong based only on two years' experience. This summer was the 5th wettest summer on record for this area, according to the Rochester, N.Y. Democrat and Chronicle, the leading local newspaper. (We live in Palmyra, approximately 20 miles east of Rochester.) Anyway, in these summers, the monarchs arrive later, or at least we start finding their eggs in our milkweed patch later, than we do in summers when it is warmer and drier. For example, comparing last summer, a normally warm one, with this summer, this summer our first egg was found 11 days later in June that last year. (In one especially warm summer, I remember finding eggs on Memorial Day). The milkweed plants also grow slower in colder summers, flower earlier and when the plant is shorter than in a normal summer. As to the numbers of monarchs we release in normal vs. wet and cooler summers, my guess is that normally we expect to release 40 to 50 monarchs a year; last year we released 39. This year we released 20; I don't recall for certain what our release number was in 1992, but I think it was less than 20. Our highest release number was something just under 120. I apologize for the imprecision. One dramatic effect we have seen in cooler and wetter summers is the infection of our milkweed plants by aphids and the sooty fungus that results in the plants. Both this summer and in 1991 we have seen this, so we have assumed the cooler and wetter weather is a causative factor. However, our milkweed patch grows much more densely than normal wild patches, based on our observations of milkweed growing in fields, so the plant density may be a factor. Some years I thin out the plants, and that may be a factor. The decision to thin them out is one we make each year, or don't; I don't like to do it, particularly after the plants have grown six or seven inches tall, because since we rely on the milkweed to draw the butterflies, and feed the caterpillars, we never know how many plants we're going to need, since we never know how many caterpillars we're going to have. Also, the flowers in groups smell gorgeous for the short time they are in bloom. Anyway, once the leaves are infected, they are no good as a food source; one year we had a substantial mortality at the pupae stage (that is, more than the one or two we normally expect not to make the transition from pupae to butterfly)which we think was related to using the infected leaves as food for the caterpillars, although it may have been coincidental. I'll also pass along an observation, since you've read this far. When the milkweed plants are in flower, it gives us an opportunity to sort of census the local populations of butterflies. Its hardly representative, but it does give us an idea of what sorts of butterflies are around, something I'm interested in because I was raised in Palmyra and spent many summer days when I was growing up chasing butterflies. Anyway, this year I was struck by the lack of butterflies; there were almost none! There are usually lots of skippers and hairstreaks, but this year there were very few. Normally I'd see 15 or 20 (admittedly, some may be the same individuals); this year I think I noticed two or three. Observations by Gary Hughs, Palmyra, NY Copyright 2000 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form