Invertebrates
Red Milkweed Beetle
Tetraopes tetraophthalmus · also called red milkweed beetles
Perched on a milkweed leaf, a bright red milkweed beetle sits motionless, its bold red-and-black warning colours a direct advertisement of the same toxic milkweed compounds it has stored away from the very plant its unseen larvae are busy feeding on underground.
Overview
The red milkweed beetle, Tetraopes tetraophthalmus, is a brightly coloured beetle native to grassland and other open habitat across a broad range of North America wherever milkweed plants grow. Its unusual four-part compound eyes, bold warning colouration, and split above-ground and below-ground feeding habits between adult and larva make it one of the more biologically distinctive milkweed specialists in North America.
A whole life built around one plant
From the larva feeding quietly on milkweed roots underground to the adult displaying warning colours on the same plant’s leaves above, nearly every stage of the red milkweed beetle’s life is tied directly to a single host plant.
Status
Least Concern — widespread and common across suitable grassland habitat throughout North America wherever milkweed plants are available.
Red Milkweed Beetle: common questions
Why is the red milkweed beetle's scientific name related to having four eyes?
This species' genus name, Tetraopes, translates roughly to "four eyes," a reference to how each of its two compound eyes is divided in half by the base of an antenna, effectively creating four separate visual fields rather than the two more typical compound eyes seen in most other beetles.
Why is the red milkweed beetle so brightly coloured?
This species displays a bright red body marked with black spots, a warning colouration that signals its unpalatability to potential predators, since it feeds on and stores toxic compounds called cardenolides from the milkweed plants it depends on, a defensive strategy shared with several other milkweed-specialist insects including the monarch butterfly and the milkweed bug.
Where do red milkweed beetle larvae live?
This species' larvae develop entirely underground, feeding on the roots of milkweed plants, a very different microhabitat from the adult beetles, which feed above ground on the leaves, flowers, and stems of the same host plant.
What sound does a red milkweed beetle make when disturbed?
This species can produce an audible squeaking sound when handled or otherwise disturbed, created by rubbing certain body parts together rather than through any vocal mechanism, a defensive behaviour that may help startle or deter a potential predator during an encounter.