ScienceShot: Glowing Roaches Mimic Toxic Beetles

Many marine creatures use bioluminescence to attract a mate or evade predators, but among land-based species it's much rarer. This makes the potential loss of a light-producing cockroach that lives in treetops in the forests of northern and central South America that much more poignant. In the first formal description of the species, scientists dub the 24-millimeter-long insect (shown in visible light, left, and under fluorescent light, right) Lucihormetica luckae. But maybe the cockroaches weren’t so lucky: The only known specimen of the insect was collected in 1939 on the slopes of Ecuador’s Tungurahua volcano, and the site was damaged when the peak erupted in December 2010. L. luckae and the other 12 species of its genus form one of only three groups of insects that can produce light (fireflies are another). The insect’s light-producing organs—two large, eyelike spots on the roach’s back, and a much smaller dot located just behind one of those spots—are bacteria-filled reservoirs in the insect's exoskeleton. New analyses of the light produced by L. luckae and its kin reveal it is identical to the light produced by click beetles in the genus Pyrophorus living in the same ecosystems, the researchers will report in a forthcoming issue of Naturwissenschaften. While those click beetles presumably generate light to warn potential predators of the highly toxic compounds they produce, the glowing cockroaches are just faking: They produce no such toxins.

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