#fecal shield

During its larval stage, the Palmetto tortoise beetle (Hemisphaerota cyanea) uses its own feces to create a defensive layer known as a "fecal shield" or "fecal thatch."

As this article explains:

Most remarkable, perhaps, is the fecal “thatch” of Hemisphaerota cyanea. In the larva of this beetle, the feces are emitted in strands, which, as they build up over the course of larval life, form a loose assemblage that totally hides the larva from view.

The construction of the "fecal thatch" begins almost immediately after the larva hatches. Each larva begins to feed within minutes of hatching, and the very first fecal strands emerge from its anal turret just a few minutes later. Subsequent strands are then produced in quick succession, and they begin to accumulate around the larva's body; as each strand emerges, it is made to curve around the larva's left or right side depending on whether the anal turret is flexed to the left or right. The direction of the curve usually alternates from one strand to the next, ensuring that a nest-like structure is formed around the larva's body.

As they emerge, the fecal strands are gathered together and then cemented into place with the help of an anatomical feature known as a caudal fork. Once an individual strand has been extruded to its full length, the anal turret is rotated upward until it comes into contact with the caudal fork, and the larva then pinches off the strand while secreting a droplet of "glue," which effectively cements each fecal strand into place against the caudal fork.

It generally takes about 12 hours for the larva to finish building its very own "fecal shield."

As an adult, the Palmetto tortoise beetle has another unusual defense mechanism: its tarsi (i.e. feet) are each lined with 10,000 tiny adhesive bristles, and when the beetle is attacked, it can press its feet flat against the surface of a leaf and secrete an oil that allows it to adhere to that surface with an enormous amount of strength. The adhesive mechanism is strong enough to resist pulling forces that are up to 60 times greater than the beetle's own weight for a full 2 minutes; it can resist even greater forces (up to 230 times greater than the beetle's own weight) for shorter periods of time.

According to this article from the University of Florida:

Each of the greatly enlarged tarsi is equipped with approximately 10,000 adhesive bristles. Each bristle has two terminal pads. When walking, only a few of the bristles touch the leaf surface. However, when attacked by a predator, the beetle puts all or nearly all of the bristles in contact with the surface and secretes oil onto the pads. With the adhesive force created by the oil between the leaf surface and tarsi, the beetle is able to clamp its hemispherical shell down tightly against the leaf and has been demonstrated to withstand pulling forces of approximately 60 times its own weight for up to two minutes. This time period is sufficient to thwart the efforts of predatory ants attempting to pry the beetle from the leaf. 

Palmetto tortoise beetles are native to the southeastern United States, and they're especially common in Florida (which is why they're also known as Florida tortoise beetles).

Sources & More Info:

Proceedings of the National Academy of Sciences: Defensive Use of a Fecal Thatch by a Beetle Larva (Hemisphaerota cyanea)

Earth Touch News Network: By the Power of the Poop-Shield: Beetle Defenses of the Faecal Kind

Cornell Chronicle: Fecal Defense: This Beetle Uses 'Overhead Sewer System' to Ward off (most) Predators, Cornell Biologists Discover

Proceedings of the National Academy of Sciences: Defense by Foot Adhesion in a Beetle (Hemisphaerota cyanea)

University of Florida: Palmetto Tortoise Beetle

Bug of the Day

The cereal leaf beetle (Oulema melanopus) is a type of beetle whose larvae use a fecal shield as a defense against predators and parasitoids, as well as a way to prevent desiccation. The gelatinous pile on top of the larvae in the photos above is the larva’s own feces. In all my research, I couldn’t find what the goo binding the fecal pellets together is!

Cereal leaf beetles are considered an agricultural pest, but are controlled in part by the parasitoid wasp, Tetrastichus julis. Females wasps will lay an egg in the beetle larva. The wasp larva will then hatch and consume the leaf beetle larva from the inside, eventually killing it.

Photos 1-4: Cereal leaf beetle larvae with fecal shields.

Photo 5: Detached fecal shield of another leaf beetle species.

Photos 6-7: Adult cereal leaf beetle.

Photos 8: Parasitoid wasp larva in the fecal shield of a cereal leaf beetle larva. Wasp larva is circled in red. Normally the wasp larva is inside the body of the beetle larva; this one seems to have missed the mark, but may still find its way there.

Photo 9: Adult wasp, Tetrastichus sp.

@aburningbentley​ submitted: This beetle had a very kind and cooperative personality and chilled on my hand for some time. I had never seen one of these before but thought "hm, this is a green beetle that looks like a shield. It should definitely be called Grüner Schildkäfer" (literally: green shield beetle). Biologists came through this time, because that is actually his German name! In English it's Green tortoise beetle, which is also fair. But he's a friend in any language :)

I love when common names are so apt! This dude is certainly in the genus Cassida, but there are a few species that look very similar and I wouldn’t say which it is with any confidence. I’d say most likely the thistle tortoise beetle (Cassida rubiginosa) or the green tortoise beetle (Cassida viridis), though! Tortoise beetles in general are super chill in my experience. And I love this dude! What a beautiful shade of green. The fun thing about Cassida beetles is their larvae carry around dried balls of poop and old bits of exuviae called fecal shields. They are apparently used in defense if you want to read about them here. Check it out: