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Small Milkweed Bug

Lygaeus kalmii[3]

The small milkweed bug is a half-inch black bug with a reddish-orange X on its back and an orange band behind the head; it is one of the easiest bugs to spot on garden milkweeds.[1][2]

Group
Insect
Order
Hemiptera
Family
Lygaeidae
US records
44 states
Sources
3 cited
Updated
2026-10-16
Small milkweed bug, black with an orange X on its back, on a milkweed pod
Small milkweed bug, black with an orange X on its back, on a milkweed pod. Photo: mefisher, public domain (CC0), via iNaturalist
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Adults are about 1/2 inch long with a reddish-orange X across the back and a reddish-orange band across the shield behind the head; a black heart-shaped mark sits in the middle of the back.[1]
  • It has a red dot on the head.[1]

Look-alikes

Look-alikeHow to tell them apart
Large milkweed bugLarger (1/2 to 1 inch) with orange-black-orange bands across each wing instead of an X.[1]
Boxelder bugHas a thin red line down the shield behind the head instead of a wide band, and lives on box elder trees.[1]
False milkweed bugVery similar but feeds on false sunflower; its black mark looks like two overlapping hearts and it has a T- or Y-shaped orange head mark.[1]

Where it lives

Widespread; found statewide in Missouri in open, grassy areas with milkweeds and other wildflowers.[1]

US map: public records from 44 states since 1990 (GBIF).

Biology and life cycle

Females lay eggs on milkweeds in spring; there is at least one generation a year and adults overwinter.[1]

In Missouri it is seen from June until the first hard freeze in October.[1]

Its bright colors warn predators that it stores toxins from milkweed sap.[1]

Damage and signs

  • It feeds mainly on milkweed seeds once they ripen, along with nectar, scavenged food and other insects, including caterpillars and the young of flies, bees and beetles.[1][2]

Health risk

None to people or pets.[1]

Control

Prevention

Usually no control is needed; gardeners growing milkweed for monarchs see it as a common milkweed visitor.[1][2]

Common questions

What is the black bug with an orange X on my milkweed?
Probably the small milkweed bug.[1][2]
Is it a boxelder bug?
No; boxelder bugs have a thin red line down the shield behind the head and live on box elder.[1]
Does it hurt milkweed?
It mainly feeds on ripening seeds; it is common on milkweed plantings.[1][2]

Sources

  1. Missouri Department of Conservation, “Small Milkweed Bug (Field Guide).” mdc.mo.gov/discover-nature/field-guide/small-milkweed-bug (accessed 2026-10-16)
  2. University of Florida IFAS Extension (EDIS, Featured Creatures), “Getting the Most out of Your Milkweed (ENY-2140).” ask.ifas.ufl.edu/publication/IN1482 (accessed 2026-10-16)
  3. iNaturalist, “Lygaeus kalmii taxon page (order and family).” www.inaturalist.org/taxa/1019598 (accessed 2026-10-06)

Updated 2026-10-16. Built from sourced records. Spot an error? Tell us.