One possibility is that the fence is a defense against ant invaders eating or damaging the eggs, or the spikes lure mites as tasty snacks for the hatchlings.
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Tia has interned at Science News, Wired.com, and the Milwaukee Journal Sentinel and has written for the Center for Investigative Reporting, Scientific American, and ScienceNow. She has a master's degree in bioengineering from the University of Washington and a graduate certificate in science writing from the University of California Santa Cruz. To find out what her latest project is, you can follow Tia on Twitter and Google+.