A new study revealed that a female parasitic wasp drills its way into fruit to lay eggs.
The female wasp uses an appendage with a zinc-tipped drill bit to pierce the tough skin of unripe figs. It has teeth that is uses for boring.
Namrata Gundiah, a mechanical engineer from the Indian Institute of Science, Bangalore, along with graduate student Lakshminath Kundanati, studied the differences between boring wasps and pollinator wasps. Boring wasps go inside figs to lay eggs, while pollinator wasps lay eggs on the fig's flowers.
The team used scanning electron microscopy to investigate the tips of the insects' ovipositors in high resolution. They discovered that the pollinator wasp has a spoon-like structure, while the boring wasp has a drill-like one. The boring wasp's ovipositor also showed tiny pits in the shaft, mostly where the structure bends, enabling the female wasp to drive the tip into fruit without breaking it. The researchers noted sensory structures along the tip that may help the wasp choose the best locations to lay eggs as well.
Gundiah and Kundanati studied the drill further by looking at the composition of the material. They focused a beam of electrons on the tip and recorded the X-ray spectra emitted by the material, and found zinc in the tooth structures.
"Zinc mainly increases the hardness, which will affect the wear resistance of the drill bits," Gundiah said in a press release.
The team also prodded the drill bit with an atomic force microscope (AFM) probe to indent it and find out how hard the zinc-laced teeth were. The recorded firmness measured out to be 0.5 GPa.
"That is almost as hard as the acrylic cement used for dental implants," Gundiah added.
The final set of tests focused on buckling forces exerted on the structure as the wasp bores into the fruit. Kundanati attached a microscope object to a video camera to film the wasps on fig trees around the campus. The video showed that the structures bent and flexed as the wasps bored into fruits. Gundiah planned to use their findings to design a minute boring tool.
The full details of the study were published in the Journal of Experimental Biology.
