Melanotrichus boydi

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Melanotrichus boydi is a plant bug in the family Miridae. It is the only insect known to feed exclusively on Streptanthus polygaloides, a plant that naturally pulls nickel into its leaves.

The nickel from the plant ends up in Melanotrichus boydi’s body, making up about 0.8% of its dry weight. This high nickel content may help protect the bug from some predators.

Streptanthus polygaloides grows on serpentine soils that are rich in nickel, which helps the plant resist many herbivores and certain pathogens. Melanotrichus boydi tolerates these high nickel levels and feeds on the plant at both larval and adult stages.

Lab tests suggest the nickel in Melanotrichus boydi can be toxic to some predators. For example, a diet of Melanotrichus boydi was toxic to the spider Misumena vatia, while other local predators were unaffected. This indicates that the plant’s nickel, carried by the bug, may provide an adaptive defense.