OE affects monarch butterflies

In the monarch enclosure and in the wild, we have come across monarch butterflies that hatch with crumpled wings.

That is a sign that the butterfly is infected with ophyrocystis elektroscirrha, or OE. As if these butterflies didn’t have enough to deal with — like excessive pesticide use, their lack of habitat and native food sources, including their host plant milkweed — OE is a debilitating parasite that was first found to infect monarch populations in the 1960s.

OE begins as a spore found on a butterfly’s scales. It could be born with it if its parent was infected or a butterfly could pick up a spore on milkweed that was scattered by another infected butterfly. An uninfected caterpillar could also eat spores on milkweed that were left by an infected butterfly.

If an infected monarch lays an egg, it will distribute OE spores on that egg and the surrounding milkweed. Then when the caterpillar hatches and eats its eggshell and the surrounding milkweed, it ingests spores that begin to replicate when the caterpillar goes into chrysalis. That butterfly will emerge from chrysalis covered in spores that will then continue the cycle.

Monarchs affected by OE may not be able to emerge from chrysalis or may emerge with damaged wings, so they will not survive. Even if they do emerge, these monarchs tend to be smaller and weaker so they may have a shorter lifespan, or if they are the generation that migrates to overwinter in Mexico they will most likely not have the endurance to be able to make it the entire distance and will die along the way.

Photo of monarch with crumpled wings

OE affects not only monarch butterflies but also queen and lesser wanderer butterflies.

The main, eastern population of monarch butterflies in North America have the lowest level of infection of OE, at about 8 percent. The western migratory population that overwinters in California has an infection rate of about 30 percent, and the non-migratory southern Florida population is heavily infected, at about 70 percent.

If you rear monarch caterpillars, the University of Kansas Monarch Watch program has guidelines of what to look for and how to help keep OE from contaminating your populations. Click here to access its page.

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