Euchaetes egle, the milkweed tussock caterpillar or milkweed tiger moth, is a moth in the family Arctiidae. It is a common mid to late-summer feeder on milkweeds and dogbane. Like most species in this family, it has chemical defenses it acquires from its host plants, in this case, cardiac glycosides (Weller et al., 1999). These are retained into the adult stage and deter bats, and presumably other predators, from feeding on them (Hristov and Conner 2005). Only very high cardiac glycoside concentrations deterred bats, however (Hristov and Conner 2005). Unpalatability is advertised with clicks from the tymbal organs (Simmons and Conner 1996).
Milkweeds (Asclepias spp.) are the most common hosts, but it is also found on dogbane (Apocynum spp.). They often prefer older plants of milkweed, and seldom share plants with monarchs Danaus plexippus, which prefer younger plants (Wagner, 2005).
These plants produce a sticky latex that can impede feeding. Early instars avoid the veins by skeletonizing the leaves. Older larvae sever the veins of the leaves that supply the latex, to reduce the flow to the area they feed on (Dussourd and Denno, 1991).
Wings are yellowish-white. The forewings have bands of beige edged in faint black across them. The body is 'hairy' and yellow, with a row of black dots down the middle of the back. Males use their tymbal organs in courtship, calling to the females, and in defense against bats (Simmons and Conner, 1996).