What is in this article?:
- New UA research has discovered that seed beetles from the desert Southwest shelter their broods from attacking parasitic wasps under a stack of dummy eggs.
The moment of truth
"I was looking at the eggs under the microscope, and I saw when I looked on the side that it seemed like there was another egg underneath it," said Deas. "I took some really small insect pins and started to scrape around the edge of the egg. Eventually I had a layer come off."
M. amicus' apparently larger egg turned out to be not one egg, but a whole stack of beetle eggs laid one on top of the other. "I was thinking: ‘Why would they do that?'" said Deas. "And I thought about the wasp."
"I went out in the field, collected a bunch of seedpods and brought them back to the lab."
Deas measured the parasitism on eggs laid individually versus on bottom eggs in a stack to see whether having one or more eggs on top was sufficient to protect the bottom eggs. And sure enough, Deas found the individual eggs were parasitized much more frequently than those eggs that were shielded at the bottom of a stack.
On the verge of what he thought was a new discovery, Deas was shocked to find that scientists before him had found the same thing in the 1920s.
"The discovery of the beetle laying eggs on top of each other is not a novel discovery," said Deas. "But they thought it's a way to compete: That the beetles are stacking eggs on top of other beetles' eggs to crush them. They didn't actually do any lab experiments to prove that those eggs are from exactly the same female."
As if one potential co-discoverer wasn't enough to dampen the spirit, another scientist had found the same egg-stacking behavior in the 1970s. "He did the same thing that I did," said Deas. "I almost thought that I had been scooped 40 years ahead of time."
But there was one big difference between Deas's work and that of his predecessor in the field. "He found like I did that some of the eggs didn't actually hatch into anything," said Deas. "He didn't specify which eggs they were."
They were the eggs on the top of the stacks, the ones most likely to be attacked by a wasp.
"I found that a lot of the top eggs didn't result in any beetles, even if they weren't parasitized. So then I started thinking, ‘Are these real eggs; what are these?'"
Now certain that he was headed into uncharted territory, Deas turned to investigating why the top eggs in a stack failed to produce any larvae.