This year has been interesting for migrating butterflies. This May (2012), Indiana and much of the Eastern US experienced large swarms of Red Admiral Butterflies. The Red Admirals appeared in Canada in larger than typical numbers. Another migratory butterfly, the Monarch has been sighted in Edmonton, Alberta, an area that Monarchs rarely visit. This poses an interesting question. How do monarchs determine when to stop migrating north?
At this time of year in Indiana, we typically see numerous Monarch Butterflies and Caterpillars. This year, however, unusual weather may be affecting monarch populations. First, we had very warm weather in early Spring, encouraging migration and egg laying. The early warmth was followed by a hard freeze that killed many of the plants and some of the early insects. Monarchs are susceptible to freezing temperatures, which may reduce populations. Since June, Indiana has had severe drought and temperatures in the 100s which stresses water-loving plants like milkweed. Some combination of factors is leading to reduced Monarch populations but we have not yet sorted it out.This Saturday, July 21, 2012, Purdue Entomology will sponsor our annual Butterfly Encounter. We expect it to be hot and to see at least a couple dozen species of butterflies. Unless we get a sudden emergence of Monarchs or influx from elsewhere, we are not certain that we will count Monarchs among the species this year.