When you are a defenseless larva, staying out of predator's preying eyes is top priority and this is where nature decides to get really creative.
Some insects might choose to mimic their environment, for example the leaf insect, which looks like a leaf or the tulip mantis which resembles a tulip. However, the larvae of the scarlet lily beetle and golden tortoise beetle decided it's best to look like bird droppings.
Scarlet lily beetles consume exclusively true lilies and are often found on their stalk, leaves, buds and flowers. They have a beautiful bright red coloring and will play dead, dropping to the ground, if threatened. However, their larvae adopted an entirely different approach to defense, one that is less action packed but equally dramatic.
Upon hatching on the underside of the leaves, the larvae will smear waste or frass, in entomological terms, all over the back of their body. This unusual disguise besides being a deterrent to predators is also a shield from the sun. This is a full grown larva without the frass covering.
Their presence might not be so visible at first but as they grow, so will their appetite as they wander to other parts of the plant. Brown clumps of frass eventually make their way to the entire plant rendering it unrecognizable.
The golden tortoise beetle larvae have the same idea in mind but their fecal shield is engineered with more precision.
They have an anal fork, a structure positioned over their body which collects old molted skin along with their own fecal material deposited using their telescopic anus. Watch how they create the shield.
Their frass contain chemical repellant due to their diet of sweet potato and related species such as morning glory and bindweed. Golden tortoise beetle larvae molt three times and retain the skin after each molt so the fecal shield literally grows with them. In addition, it is movable so the larvae can angle the shield to protect themselves from an attack. Watch as the contraption opens and closes.
However ingenious as it may seem, it is effective only with smaller critters while birds or larger insects are still not deterred. We watched as 3 larvae on our morning glory was picked off in consecutive days leaving zero adult golden tortoise beetle for us to observe.
