Small Milkweed Bug – Lygaeus kalmii

Small Milkweed Bug – Lygaeus kalmii
Family Lygaeidae
(seed bugs)
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Live adult bugs photographed in the wild at McKee Marsh Forest Preserve, DuPage County, Illinois.

Small Milkweed Bug

Milkweed bugs are usually found in groups on milkweed plants, often on the underside of the leaves. I have seen them in conglomerations of hundreds. The plant produces a milky white sap when a leaf is removed. These plants are large (3-4 feet high) with sprays of small white flowers in the summer. In the fall, seed pods develop which are 4 inches long and 1 1/2 inches wide. When the seeds ripen, the seed pods open up releasing the seeds which float on fluffy white parasols. Milkweed bugs can be found on seed pods piercing the wall of the pod to feed on seeds.  Milkweed bugs are one of a small group of insects that have the ability to tolerate the toxic (poisonous) compounds in the milkweed plant. They are therefore important in regulating populations of this plant.

Milkweed bugs have few predators because they concentrate in their bodies bad tasting compounds found in the sap of milkweed plants. The bugs use their bright colors to advertise their bad taste. Inexperienced birds that taste their first milkweed bug are unlikely to try to eat another orange and black insect, such as a Monarch or Viceroy butterfly.

Small Milkweed Bug

Both small and large milkweed bugs have incomplete metamorphosis. The nymphs (immatures) look like the adults except that they do not have full wings and their color pattern is different. Black wing pads appear early in their development. Nymphs have bright orange abdomens, and usually molt 5 times  before becoming an adult. Eggs take about 1 week to hatch and a month to become adults.
Small Milkweed Bug

  1. John L. Foltz, University of Florida, Dept of Entomology & Nematology, Hemiptera: Miridae,  2001.
  2., Lygaeus kalmii
  3. Alfred G. Wheeler and Sir T. Richard E. Southwood FRS, Biology of the Plant Bugs
  4. American Museum of Natural History, National Science Foundation and University of New South Wales, Plant Bug Planetary Biodiversity Inventory, Plant Bugs (Miridae)

Order Hemiptera: True Bugs number almost 5,000 species in North America, and 40,000 worldwide. They have mouthparts formed into a beak, adapted for sucking plant juices or the liquefied insides of their animal prey.
Suborder Auchenorrhyncha – Cicadas & Planthoppers
Suborder Sternorrhyncha – Aphids, scales, mealybugs, jumping plant lice