Milkweed leafs
Illinois has caterpillars that include the brown hooded owlet moth and monarch butterfly. Other caterpillars that are found in Illinois include the Asteroid, white-marked tussock moth, yellow-marked tussock moth, milkweed tussock moth, and the viceroy caterpillar.
The accepted scientific name is Euchaetes egle.
Milkweed is eaten by several species of insects, most notably the monarch butterfly larvae, red milkweed beetle, and milkweed tussock caterpillar or tiger moth. In turn, monarchs are eaten by birds, and tiger moths by bats.
They are a native insect that naturally feeds on milkweed plants. If by "bad" you mean are they an invasive or pest species, then no, they are not bad. Some people are allergic to their hairs though, so be careful with them...
The rusty tussock moth (Orgyia antiqua)
Torolf R. Torgersen has written: 'Identification of parasites of the Douglas-fir tussock moth, based on adults, cocoons, and puparia' -- subject(s): Identification, Parasitic insects, Douglas-fir tussock moth, Parasites 'Douglas-fir tussock moth handbook' -- subject(s): Control, Douglas-fir tussock moth
Tussock moth caterpillars are relatively toxic to other animals. If a dog ingests one, it could get very sick from the poison.
a tussock moth
Richard R Mason has written: 'Douglas-fir tussock moth handbook' -- subject(s): Larvae, Douglas fir tussock moth
It has a type of sex maniac poison
1 week
Jeffrey Alan Millstein has written: 'The population dynamics of the douglas-fir tussock moth' -- subject(s): Moths, Insect populations, Douglas-fir tussock moth