Whorled Milkweed

The nectar of the flowers attracts many kinds of insects, including honeybees, bumblebees, Halictid bees (Halictus spp., Lasioglossum spp.), Halictid cuckoo bees (Sphecodes spp.), sand-loving wasps (Tachytes spp.), weevil wasps (Cerceris spp.), Sphecid wasps (Sphex spp., Prionyx spp.), Five-banded Tiphiid Wasp (Myzinum quinquecinctum), Northern Paper Wasp (Polites fuscatus), spider wasps (Anoplius spp.), Eumenine wasps (Euodynerus spp., etc.), Syrphid flies, thick-headed flies (Physocephala spp., etc.), Tachinid flies, flesh flies (Sarcophagidae), Muscid flies, Painted Lady (Vanessa cardui) and other butterflies, Peck's Skipper (Polites peckius) and other skippers, Squash Vine Borer Moth (Melittia cucurbitae) and other moths, and Pennsylvania Soldier Beetle (Chauliognathus pennsylvanicus); sources of information include Robertson (1929) and personal observations. Among these floral visitors, bees and wasps are usually more effective at cross-pollination. Some insects feed destructively on the foliage, flowers, seedpods, and other parts of Whorled Milkweed. These species include the Small Milkweed Bug (Lygaeus kalmii), Milkweed Leaf Beetle (Labidomera clivicollis), Yellow Milkweed Aphid (Aphis nerii), and a moth, the Delicate Cycnia (Cycnia tenera). Although this insect does not occur in Illinois, in the southwestern United States, the Horsetail Milkweed Longhorn (Tetraopes discoideus) feeds on Whorled Milkweed and closely related milkweed species (Asclepias spp.); sources of information include Betz et al. (1997), Yanega (1996), and personal observations. Mammalian herbivores usually avoid the foliage of Whorled Milkweed as a food source because it is one of the more toxic milkweed species.