These Baby Beetle backpacks are made of stool

All children poop, but only a few are skilled enough to turn their poop into architecture. Before tortoise beetles molt into adults, they molt as larvae. To protect their soft bodies from the outside world, baby beetles protect themselves with an umbrella made of their own excrement, protruding precariously from their anus. The tiny beetles build their dung shields with the help of a special telescopic anus, which can extend and twist like an elephant’s trunk to deposit fresh droppings on top of their shield. The armor helps the larvae pass through as unappetizing piles of feces, escaping the prying eyes of predators.

A paper recently published in the journal ZooKeys It describes, in extraordinary detail, the precise process behind the fecal awns of many species of tortoise beetles, a distinct shield-building group within the leaf beetle family, or Chrysomelidae. “It’s a beautiful library, you know, with all this information about tortoise beetle fecal shields,” said Lynette Strickland, a biologist at Boston University who studies tortoise beetles and was not involved in the new paper. “I mean a very specific library.”

Poop parachutes are no secret to scientists who study tortoise beetles, the adolescence stage the insects go through on their way to adulthood. But no research has focused on the detailed art of constructing these shields. “I didn’t know that tortoise beetle larvae could protrude an anus and use it in construction,” Strickland said. “I didn’t know that!”

Aside from its elegant taste and some stinky shades, what good is a fecal umbrella to a baby ladybug? Scientists have suggested that shields have multiple functions. They may protect the larvae from the elements, disguise them as droppings or dead plants, or even deter predators and parasites with their unpleasant odor and potential chemical deterrent. After building its canopy, the beetle larvae are able to do so a movement– Rotate the shield up and down, lower it onto their back and sway it from side to side. The caterpillars even use their shields like a club to ward off would-be intruders, according to Carolyn Chapo, a research associate at the Nebraska State Museum at the University of Nebraska-Lincoln and author of the new paper. Some tortoise beetle larvae live in groups Form a ring With their heads in the middle and the fecal umbrellas facing outward, it is a united front of defence. “Then they move together,” Chapo said.

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As larvae, tortoise beetles are small, dull larvae. But adult beetles are really beautiful. They get their common name from their domed upper shell, which is similar to a tortoise shell in shape and gemstone-like in color. Perhaps the boldest of the bunch are golden tortoise beetles, which look like nuggets of gold that have suddenly sprouted with their legs. “When you see them landing on a plant, you could mistake them for a drop of water,” said Shabo, who said she decided to study tortoise beetles because of their beauty. (When she was narrowing her search, she was choosing between tortoise beetles and stink bugs, which could be… more beautiful than you might assume.)

Golden tortoise beetle perched on the edge of a leaf. credit: Pavel Kirillov, CC-by-sa-2.0 via Flickr.Pavel Kirillov, CC BY-SA 2.0, via Flickr

When Chapo began studying beetles in natural history collections, she quickly noticed a gap in the archives. About 99 percent of the collections were adults, which were dried and mounted in trays; Juvenile sponges were mostly absent. “Each stage of the insect explores the environment in a different way,” Chabo said. “The adults usually fly and mate, and the larvae are the ones that actually feed.” So Chabo decided to try observing tortoise beetles from the egg stage to adulthood so she could document how the larvae build, maintain and use their fecal parachutes.

Strickland, who breeds the neotropical tortoise beetle Chelymorpha alternatives In her lab, she has always been fascinated by larval fecal parachutes. “I always thought he was really cute,” she said. Strickland describes the shape of the carapace of these specific beetles as a bubble. “They don’t really put a lot of effort into it,” they said. But Strickland has never observed how beetles build, add to or process their fecal shields, in part because the larvae are so small.

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Tortoise beetles are not the only species with a larval structure. Tiger beetle larvae build mud towers over their tunnels to prevent flooding. Caddisfly larvae make decorative cocoons from pebbles and leaves. The larvae of the fungus beetle A back bag of their molted skins, or pelts, which may serve as a decoy for predators. Feces may be an unconventional building material, but it is free and somewhat inexhaustible. “In general, insects are very clean animals,” Chapo said, noting that the tortoise beetle’s droppings are separate structures raised high above the body, unlike some other leaf beetles that carry their droppings on their bodies. “Which I find disgusting,” she said. “I even have standards!”

Tortoise beetle bearing a fecal shield as seen from above
Beautiful fecal umbrella. Very balanced! Credit: K. Nishida

The approximately 3,000 species of tortoise beetles produce a variety of fecal structures, influenced by the nature and arrangement of their waste. Some species have wet stools, while others have drier stools. “Some of them come out in the form of long threads, and some of them come out in the form of wet spots,” Chapo said. Some larval tortoise beetles make fan-shaped shields, while others arrange their feces Spiral coil They resemble bird nests.

Chapo and his colleagues focused on comparing the fecal armor of a few species of tortoise beetles, including… Calyptocephala attenuatawhich is located in Costa Rica, and Cassida sphaerula, which is located in South Africa. Researchers gained access to a large population of beetles in South Africa thanks to Sally Adam, an amateur naturalist and author of the paper. In August 2021, Adam found some tortoise beetle larvae and pupae swarming in some yellow daisies on her farm. She started raising insects as a hobby during the COVID-19 pandemic, watching ant and dragonfly eggs hatch in her office. She raised tortoise beetle larvae to adulthood and posted photos of the insects on iNaturalist. And soon someone identified the type –Cassida sphaerula– I told her that the larval and pupal stages of beetles had never been recorded before.

Adam began to experiment with Shabu’s directions. “I was feeling a little overwhelmed until I remembered that a retired academic friend of mine had a microscope and a camera,” Adam wrote in an email during a live stream of the Global Sheepdog Trials. Adam removed some of the shields entirely, leaving the larvae bare, and removed only part of the shields of other beetles. In both cases, the larvae very carefully reconstructed their fecal awns. If part of its diamond-shaped carapace is broken, the larvae deposit new feces on the broken side to re-create a balanced carapace.

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Amazing anus in action! Credit: K. Nishida

A maneuverable, telescopic anus is the only tool tortoise beetle larvae need to build their armor. Legs and mouth parts are not necessary here. “It’s just a long tube that comes out and moves around, and it can extend almost to the animal’s head,” Chapo said. When Adam saw her anus delicately place a drop of feces over the shield, she “squealed with delight,” she said. (If you want to see tortoise beetle larvae squeezing out a wet drop of dung to add to their canopy, Take your time.) South African beetles also layered their ancient, molted skins, or scions, into their armor, likely for reinforcement. “It’s not a one-time thing,” Chapo said. “They build it the same way. They repair it the same way, always trying to balance the armor.”

The researchers’ larger argument in the new paper is that tortoise beetle larvae should be recognized as architects in their own right, just like more famous builders such as ants, bees, wasps, termites and spiders. The building instinct permeates the animal tree of life, as animals have developed innovative ways to protect themselves from the harsh environment. “People like them can always think of beavers today as an example of an organism that changes its environment around it to suit them,” Strickland said. “These insects do that too, right? These little creatures actually build things and have really complex behaviors.” Baby beetles may not yet know how to build feces, but they certainly can build with it.

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