Tropidothorax leucopterus

Tropidothorax leucopterus · Order: Hemiptera · Family: Lygaeidae

No source yet on danger. We have no source yet on whether it bites, stings or damages anything.
Tropidothorax leucopterus
Photo: Ettore Balocchi, CC BY

Tropidothorax leucopterus is a small true bug about 9 to 10 mm long, with an oval-elongated body in striking red and black warning colors. Its head is black with a tiny red spot, the pronotum has black margins and a front red stripe, while the wings show a red corium and a black-matt membrane with a white spot. It feeds mainly on white swallow-wort and broadleaf milkweed, storing plant toxins that make it poisonous and cause birds to avoid it.

Source: Wikipedia

How to recognize it

The bug’s body is oval-elongated and brightly colored in red and black, with a black head bearing a small red spot. The connexivum shows alternating black and red spots, the abdomen is red with black spots, and both antennae and legs are black.

Source: Wikipedia

Size

Adults reach a length of about 9 to 10 mm (0.35 to 0.39 in).

Source: Wikipedia

Where it lives

They are found on their host plants white swallow-wort and broadleaf milkweed.

Source: Wikipedia

Life cycle

Their red-black coloration warns predators because they store toxins from their poisonous host plants. Birds learn to avoid them after encountering the warning colors.

Source: Wikipedia

Where it comes from

In Europe it is recorded from many countries including France, Germany, Italy, Spain and others.

Source: Wikipedia

More photos

Tropidothorax leucopterus photo 3
Photo: Kostas Zontanos, CC BY
Tropidothorax leucopterus photo 4
Photo: Kostas Zontanos, CC BY

Questions people ask

What does Tropidothorax leucopterus look like?

It is a small, 9 to 10 mm bug with an oval body in bright red and black, a black head with a tiny red spot, and wings that are mostly red with a matte black membrane.

Source: Wikipedia

Is this bug poisonous?

Yes, it stores toxins from its host plants, making it poisonous and causing birds to avoid it.

Source: Wikipedia

Same family (Lygaeidae)

Large Milkweed BugLarge Milkweed BugOncopeltus fasciatusSmall Milkweed BugSmall Milkweed BugLygaeus kalmiiFalse Milkweed BugFalse Milkweed BugLygaeus turcicusIndian Milkweed BugIndian Milkweed BugSpilostethus pandurusDamages trees, gardens or cropsBlack-and-Red BugBlack-and-Red BugLygaeus equestrisHarlequin bugHarlequin bugSpilostethus saxatilisDamages trees, gardens or crops

Sources

  • Wikipedia: https://en.wikipedia.org/wiki/Tropidothorax_leucopterus

Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia

Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.

How this page works

This is one bug's fact sheet. The colored box at the top says whether it is dangerous. Sections below cover how to recognize it, whether it is a pest, and how to deal with it. The US map shows which states have records; tap a state to see other bugs there.

Every fact on Bug FAQ comes from a named source (university extension sites, government agencies, GBIF, iNaturalist, Wikipedia). The source is linked next to each section. If we have no source for something, we leave it out.