For many insects, their “ears” aren’t located anywhere near their heads. Crickets have evolved organs on their front legs that allow them to detect sound. Meanwhile, moths, mantises, and cicadas gather auditory information from similar appendages on their thoraxes or abdomens. For years, entomologists assumed that organs on certain stink bug legs must function in the same way. However, new research proves the truth is more complex—and creepy.
Detailed in a study published on October 16 in the journal Science, biologists collaborating across multiple universities in Japan show that the females in a subset of around 100 stink bug species known as Dinidoridae don’t have tympanal organs––the name for an insect’s auditory system. Instead they possess a, “previously unknown type of symbiotic organ” that is integral to their reproductive process. Instead of a membrane-like surface seen on other bugs, the leg organ is composed of a waxy covering dotted with several thousand pores connected to porous glands. Over the course of their lives, these stink bugs selectively acquire a benign, Cordyceps-related fungus that attaches and grows from these pores on their legs. When it’s finally time for the next generation of insects to arrive, the stink bugs encase their eggs with a web of growing fungi harvested from their leg organs.
The bizarre process has a purpose beyond giving you goosebumps. Like many other insects, stink bugs are a favorite target for parasitic wasps. The fungi acts like a suit of armor, preventing female wasps from laying their own progeny in the stink bug eggs, according to the team’s lab experiments. . During subsequent trials in which the fungus was removed, the wasps fed on the stinkbugs more frequently. At the same time, the fungus never infects the wasps themselves, meaning the protection it gives to the stinkbugs is purely mechanical and not like a contagious virus.
“The previous interpretation that the female-specific hindleg organ might be a tympanal ear was based merely on superficial morphological resemblance,” the study’s authors explained in an accompanying announcement.
The team also describes the unique partnership between bug and fungus as an “impressive example of how evolutionarily novel traits for microbial symbiosis emerge,” especially one that encompasses so many molecular, morphological, cellular, and behavioral traits.
The fungi-carrying stink bugs mostly live in Asia and northern Africa, but it’s totally understandable if you live elsewhere and suddenly feel the need to take a shower. Just because it’s a wonder of nature doesn’t make it any less nightmarish. Meanwhile, Dinidoridae’s relatives are causing havoc elsewhere. Across North America, the invasive brown marmorated stink bug (Halyomorpha halys) is costing billions of dollars in agricultural damage every year. That’s when it’s not generating its acrid, defensive namesake from its own glands.
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