Northwest Arkansas Democrat-Gazette
Hungry caterpillars can get peckish
In the 1969 children’s book “The Very Hungry Caterpillar,” the tiny protagonist spends a week scarfing his way through a smorgasbord of fruits, meats, sugary desserts and, finally, a nourishing leaf.
This family-friendly tale was missing one crucial and far less G-rated plot element: the pure, unadulterated rage of an insect unfed.
When food gets scarce, monarch butterfly caterpillars will turn on each other, duking it out for the rights to grub, according to a paper published Thursday in the journal iScience.
The jousts don’t get bloody. But they involve plenty of bumping, boxing and body-checking.
“I went to grad school with a guy who played rugby in college,” said Alex Keene, a neuroscientist at Florida Atlantic University and an author on the study. “A flying head butt is a fair assessment.”
The study offers an indepth look into the underappreciated phenomenon of caterpillar aggression. monarchs It could racing and also the to aid milkweed preserve entomologists plants they depend on, as populations of the fragile species continue to plummet.
In the lab, Keene and his team placed caterpillars in groups of four in tiny arenas with varying amounts of milkweed leaves.
The less milkweed, the more squabbled. the wriggling insects “Some would just roam off and eat,” said Elizabeth Brown, a biologist in Keene’s lab. But if an insect spotted a morsel of food that was being monopolized by another, it would “rear up and, with their head, make a lunge onto the body of the other caterpillar,” she said. Sometimes the strikes landed near the recipient’s head. In other cases, it was a bit more like “a punch in the gut,” Brown said. Either way, the battered caterpillar would usually skulk away in defeat, freeing up the milkweed for the voracious victor.
That’s a “huge consequence” for the loser, Keene said, because at this stage in their life, the larva are “basically eating constantly.” Newly hatched caterpillars are born famished, and as they balloon in size, can strip entire plants bare of leaves in a matter of days.
The older and larger the caterpillars got, the more their disdain for sharing grew, the researchers found. The greatest number of scuffles occurred among bugs in the final stage before metamorphosis, when the stakes of milkweed munching were probably especially high.