Why Do Some Monarch Butterflies Have Crumpled Wings?

The culprit is parasites and the damage can't be fixed

A monarch with deformed wings may be infected with parasites.

Debbie Hadley / WILD Jersey

Reports about the decline of monarch butterflies in North America have stirred the nature-loving public to take action, hoping to reverse the trend. Many people have planted backyard milkweed patches or installed butterfly gardens and started paying closer attention to the monarchs that visit their yards.

If you've begun to observe the monarch butterflies in your area, you've probably discovered that many monarchs don't make it to adulthood. Some will make it through the pupal stage only to emerge as deformed adults with crumpled wings, unable to fly. Why are some monarch butterflies similarly deformed?

Why Monarchs Have Crumpled Wings

A protozoan parasite known as Ophryocystis elektroscirrha (OE) is most likely to blame for a monarch butterfly with crumpled wings. These single-celled organisms are obligate parasites, meaning they require a host organism in which to live and reproduce. Ophryocystis elektroscirrha, a parasite of monarch and queen butterflies, was first discovered in butterflies in Florida in the 1960s. Scientists have since confirmed that OE affects monarchs worldwide and is believed to have co-evolved with monarch and queen butterflies.

Monarch butterflies with high levels of OE infection might be too weak to emerge completely from the chrysalis and sometimes die during emergence. Those that do manage to break free of the pupal case might be too weak to hold on long enough to expand and dry their wings. An OE-infected adult might fall to the ground before its wings are fully open. The wings dry wrinkled and folded, and the butterfly is unable to fly.

These deformed butterflies won't live long and cannot be saved. If you find one on the ground and want to help it, place it in a protected area and give it some nectar-rich flowers or a sugar-water solution. There is nothing you can do to fix its wings, however, and it will be vulnerable to predators since it cannot fly.

Symptoms of OE Infection

Monarch butterflies with low OE parasite loads might not show symptoms of infection. Individuals with high parasite loads may exhibit any of the following symptoms:

Infected Pupa

  • Dark spots that become visible a few days before the adult is expected to emerge
  • Unusual, asymmetrical coloration of the adult butterfly while still within the pupal case

Infected Adult Butterfly

  • Weakness
  • Difficulty emerging from the chrysalis
  • Failure to emerge from the chrysalis
  • Failure to cling to the chrysalis upon emergence
  • Crumpled or wrinkled wings that aren't fully expanded

Although monarchs with low parasite loads may appear healthy, be able to fly, and reproduce, they might still be affected by the parasites. OE-infected monarchs are often smaller, have shorter forewings, and weigh less than healthy, parasite-free monarchs. They are weaker fliers and prone to desiccation. Male monarch butterflies infected with OE are less likely to mate.

Testing for OE Infection

According to researchers at the University of Georgia, OE infection rates vary between different monarch butterfly populations in North America. Non-migratory monarchs in southern Florida have the highest OE parasite infection rates, with 70% of the population carrying OE. About 30% of western migratory monarchs (those living west of the Rocky Mountains) are infected with OE. Eastern migratory monarchs have the lowest infection rate.

Infected butterflies don't always exhibit symptoms of OE, but you can easily test a butterfly for OE infection. Infected monarch adults have OE spores (dormant cells) on the outside of their bodies, particularly on their abdomens. Scientists sample OE parasite loads by pressing clear Scotch tape on a butterfly's abdomen to pick up the OE spores. OE spores are visible—they look like tiny footballs—under magnification as low as 40 power.

To test a butterfly for OE infection, press a piece of ultraclear tape against the butterfly's abdomen. Examine the tape under a microscope and count the number of spores in a 1 cm by 1 cm area.