Hi Sidney,

Thank you for contacting the UVM Master Gardener Helpline and providing a photo. The insects on your milkweed plants are the milkweed tussock moth caterpillars (Euchaetes egle) also referred to as the Milkweed Tiger Moth. Although the Milkweed Tussock Moth Caterpillars seem like they are doing a lot of damage to the milkweed they are a native species and can live along side the Monarch caterpillar. Just like monarchs, these species have evolved to be able to eat and accumulate milkweed toxins in their bodies as a defense mechanism against predators. The monarch caterpillars tend to favor the more tender leaves of younger milkweed plants while the milkweed tussock caterpillars you see are mainly consuming the older, more coarse foliage.  Therefore both monarch and milkweed tussock moth caterpillars can coexist together on the same plant. Although they may devour some of your plants faster than the monarch caterpillars can, milkweed tussock moth caterpillars are not causing actual harm. It might look like they have destroyed the milkweed plant but the milkweed does just fine and lives to send out many more plants the next year.

In the interest of having a diverse population of pollinators in the garden, we do not recommend control or removal of milkweed tussock caterpillars, since they are a natural part of our ecosystem. If you decide you absolutely must remove them, you can do so by hand picking them or putting in a bucket of soapy water while wearing protective gloves since their hairs can cause an uncomfortable rash in some people. I am hoping you have enough milkweed to share!

Below are links with additional information on milkweed tussock moths and their caterpillars.
https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

https://extension.unh.edu/blog/2019/08/what-are-hairy-caterpillars-eating-my-milkweed-are-they-good-bugs

stages:  https://www.marylandbiodiversity.com/view/2513

I hope this helps and happy gardening!