There are two true bugs (family Lygaeidae, order Hemiptera) that are associated with milkweed mostly in late summer and fall, the large milkweed bug and the small milkweed bug. Large milkweed bug with mouthparts inserted into common milkweed seed pod. Instead the moth evolved to produce ultrasonic clicks from their tymbal organs which bats quickly learn is associated with a noxious mouthful and then avoid the moth as prey. Since the primary predators of the moths are bats, which hunt at night using sound rather than sight to locate prey, the moths don’t need warning coloration.
Like the monarch caterpillar, this species also sequesters cardiac glycosides and retains them in the adult body. The small white eggs (L) hatch into small cream-colored larvae with black heads (LC) that develop hairs in the second instar (C) and by the third instar have thick tufts of hairs (RC) that are incorporated into the cocoon that protects the pupa (R). This species has a single generation per year in the north (two or more in the south). The mature larvae drop to the ground and produce a gray cocoon, incorporating hairs from the caterpillar, where they pupate to become adults or overwinter. Milkweed tussock caterpillar is seldom in competition with monarch caterpillars, as they generally feed on older shoots while monarchs prefer younger shoots. The older caterpillars sever major leaf veins to reduce the amount of latex sap encountered. These larger caterpillars wander about so they may be seen alone or in small groups from mid to late summer on common milkweed ( A. By the third instar the caterpillars have thick tufts of black, white and orange (sometimes yellow) hairs covering the body. Initially the caterpillars with black head capsules are pale and hairless, and second instar caterpillars have sparse spines or hairs.
The gregarious early instars skeletonize whole leaves, feeding only on the tissues between the veins, thereby avoiding the copious latex sap. Milkweed tussock moth caterpillars feed together in large groups in the early instars. The female lays masses of white eggs on the underside of leaves (R). The adult milkweed tussock moth has dull gray wings (L) and a yellow-orange abdomen marked with black dots (LC and RC). The female moth lays fuzzy white masses of eggs on the underside of the leaves. Found throughout eastern North America, this moth with a wing span up to 1¾ inches, has dull grey, mostly unmarked wings and a hairy yellow-orange abdomen marked with black dots.
A few other milkweed specialists have developed ways to “eat around” the sap to avoid its toxic effects.Īnother caterpillar that specializes on milkweeds is the milkweed tussock caterpillar or milkweed tiger moth, Euchaetes egle, in the family Erebidae, subfamily Arctiinae (formerly family Acrtiidae). This is why so many insects found on milkweed plants have conspicuous red or orange colors or markings. The insects that have this ability typically have aposematic markings, or warning coloration, advertising their toxicity. Milkweed bugs have bright red or orange aposematic (warning) coloration.Īnd just like the monarch caterpillars which sequester and concentrate the toxins in their own bodies, giving them a bitter taste and protection against predators, many other milkweed insects – including milkweed bugs, milkweed longhorn beetles, and milkweed leaf beetles – have developed ways for using the toxins in their own defense, too. The flowers and nectar of milkweeds, however, do not contain these chemicals so nectar-seeking bees, flies, and butterflies can pollinate the plants without being affected. Other insects besides monarchs visit milkweed flowers. Only certain insects which have evolved to be able to deal with those chemicals without being poisoned can thrive on the plants, and have become specialists on milkweeds. The sticky white sap that gives milkweed its common name and the leaves contain toxic chemicals (cardiac glycosides) to deter mammals and insects from feeding on the foliage. Not many insects are able to feed on milkweeds. But if you’ve ever grown or just observed milkweeds, likely you’ve encountered some other insects on those plants. Monarch butterfly ( Danaus plexippus) caterpillars are probably the one insect most people associate with milkweeds ( Asclepias spp.).