"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.
Insect warfare: dummy eggs protect the young
"I actually took the eggs and weighed them. I weighed individual eggs and bottom eggs from a stack and then top eggs from a stack." Deas found that the individual eggs that had not been stacked weighed the same as the bottom eggs in a stack. But the top eggs only weighed half as much."
"The beetles are somehow able to reduce the size of these eggs before they lay them. They're able to control how big that top egg is so that they can save resources."
Deas believes that the top eggs simply don't have enough nutrients to fully develop a beetle or a wasp.
"If a wasp attacks it, the wasp larvae have reduced survivorship," said Deas
|Contact: Daniel Stolte|
University of Arizona