World’s Smallest Fly

Photo: Inna-Marie Strazhnik; (inset) S.D. Porter/ARS/USDA

Scientists have discovered a new fly so small that it's tinier than a grain of salt. But small size ain't the only weird thing about the tiny phorid fly Euryplatea nanaknihali: it lives inside the decapitated head of ants.

The flies lay their eggs in the body of the ant; the eggs develop and migrate to the ant's head where they feed on the huge muscles used to open and close the ant's mouthparts. They eventually devour the ant's brain as well, causing it to wander aimlessly for two weeks. The head then falls off after the fly larva dissolve the membrane that keeps it attached.
The fly then takes up residence in the decapitated ant head for another two weeks, before hatching out as a full-grown adult. In this case, researchers think the fly parasitizes tiny acrobat ants, whose heads are about as large as the fly itself and grow to about 0.16 inches (4 millimeters) long.

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