#141 Red Milkweed Beetle

Red Milkweed Beetle (Tetropoes tetrophtalmus)


A beetle in the family Cerambycidae. The binomial genus and species names are both derived from the Ancient Greek for “four eyes.” As in many longhorn beetles, the antennae are situated very near the eye–in the red milkweed beetle, this adaptation has been carried to an extreme: the antennal base actually bisects the eye. The milkweed beetle, a herbivore, is given this name because they are generally host specific to milkweed plants (genus Asclepias). It is thought the beetle, which as an adult feeds on the foliage of the plant, and its early instars, which eat the roots, derive a measure of protection from predators by incorporating toxins from the plant into their bodies, thereby becoming distasteful, much as the monarch butterfly and its larvae do. They feed by opening veins in the milkweed plant, decreasing the beetles’ exposure to latex-like sap. When startled, the beetles make a shrill noise. When interacting with another beetle, they make a ‘purring’ noise. The red and black coloring are aposematic, advertising the beetles’ inedibility. There are many milkweed-eating species of insect that use the toxins contained in the plant as a chemical defense. Red milkweed beetles lay egg-clutches in mid-summer near the roots of the milkweed.

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