Milkweed Bug

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The bond between monarch butterflies and milkweed plants is a good story. Monarchs cannot survive without milkweed. Monarch caterpillars need milkweed plants (Asclepias spp.) to grow and develop, and female monarch butterflies only lay their eggs on milkweed. The caterpillar/larvae capture and store toxic steroids, known as cardenolides, from milkweed and they use these cardenolides as a Monarch Butterflydefense against predators. The bad taste and toxicity of both the larvae and adults are advertised by eye-catching, warning coloration that we find so beautiful. When a bird or other predator tastes a monarch, it learns to associate this color pattern with the bad taste, and avoids preying on monarchs in the future.

However, plants use a variety of self-defense tactics against the animals that eat them, and the cardenolides in milkweeds are there to protect the plants, not to protect the monarchs eating them. The uninvited larvae Asclepias tuberosadiners can have a difficult time when the milky latex oozing from the damaged milkweeds gums up their mandibles so that they can no longer eat. Larger larvae have even been shown to chew through the main vein of the leaf early on so that the flow of latex to the rest of the leaf is stopped and dinner can continue without interruption.

Milkweed plants develop large fleshy seed pods. When the seeds are mature, the pods pop open, freeing the seeds. Lots and lots of them. Attached to the seeds are fine tufts of hairs (called pappus) which help spread the seeds like mini parachutes in the wind carrying the seeds away from the plant. Milkweed is also a great host plant for many beneficial insects including bees, beetles, and lady beetles (ladybugs), milkweed bugs, milkweed longhorn beetles, and milkweed leaf beetles. Some of these have also developed ways for Milkweed bugs on Milkweedusing the toxins for self-defense too and show bright orange and black warning coloration as well.

As common milkweed (Asclepias syriaca) produces its signature spiny, oblong seed pods, milkweed bugs may show-up to take advantage of the seed bounty. The seeds are arranged in rows that overlap and each pod may contain hundreds of seeds. There are two species of bugs that feed on milkweed seed:  the large milkweed bug (Oncopeltus fasciatus) and the small milkweed bug (Lygaeus kalmii). The Lee County Pollinator Haven at the McSwain Agricultural Education Center located at 2420 Tramway Road in Sanford is currently host to dozens of various pollinator species and the plants that attract them. Many varieties of butterflies, moths, birds, beetles, bees and other flying insects visit us daily. We invite you to come walk the paths and see these beneficial insects collect nectar, pollen, and other food while you enjoy the beauty of pollinator matched plants that work well in our area. Docent tours can be arranged for groups by contacting the Master Gardener℠ volunteers in Lee County at 919-775-5624.

Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.

Written By

Minda Daughtry, N.C. Cooperative ExtensionMinda DaughtryExtension Agent, Agriculture - Horticulture Call Minda E-mail Minda N.C. Cooperative Extension, Lee County Center
Updated on Sep 6, 2019
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