The tephritid fly Zonosemata vittigera (Coquillett) has a leg-like pattern on its wings and a wing-waving display that together mimic the agonistic territorial displays of jumping spiders (Salticidae). Zonosemata flies initiate this display when stalked by jumping spiders, causing the spiders to display back and retreat. Wing transplant experiments showed that both the wing pattern and wing-waving displays are necessary for effective mimicry: Zonosemata flies with transplanted house fly wings and house flies with transplanted Zonosemata wings were attacked by jumping spiders. Similar experiments showed that this mimicry does not protect Zonosemata against nonsalticid predators. This is a novel form of sign stimulus mimicry that may occur more generally.