Giants of the Night
The moth flutters silently, mysteriously through the night. Her wings are impossibly large and glow green like an emerald in pale moonlight. She is a luna moth, named for the moon, for the night, and on this, her last evening on Earth, she’s searching for a place to lay her eggs.
Big, Fluffy and Fluttery
Luna moths belong to the silk moth family of insects. About 1,500 kinds of silk moths flutter worldwide. Most live in tropical places, but 13 kinds live in Missouri. Silk moths have fuzzy bodies and velvety wings that out-bling many butterflies. Some silk moths have wing spots that look like large, glaring eyes. When the moths unfold their wings, the eyespots show, scaring away would-be predators. Silk moths are some of nature’s largest insects. The atlas moth of Southeast Asia is bigger than a dinner plate, and Missouri’s largest moth, the cecropia moth (shown below), is larger than some songbirds!
Chubby Green Eating Machines
Once they hatch, baby silk moths have one thought in their squishy little brains: food. Silk moth caterpillars eat their eggshells, then chow down on leaves. Newborn caterpillars are mosquito-sized, but soon grow long and chubby. Older caterpillars grow fleshy spikes that appear dangerous, but io moth caterpillars are the only silk moth caterpillars in Missouri that can sting with their spikes.
Cecropia, polyphemus and luna caterpillars grow as big as your dad’s pointy finger, but regal moth caterpillars (shown below) win first prize for size. Called hickory horned devils because of their inch-long spikes, these eating machines stretch 6 inches long—about the size of a hot dog!
From Beastly to Beautiful
After two months of near-constant eating, silk moth caterpillars chomp their last leaf then search for somewhere to turn into a pupa (pyoo-puh). Think of a pupa as a silk moth’s teen years—a time when the baby caterpillar grows into an adult moth. Regal and imperial caterpillars burrow underground to pupate. Other caterpillars spin cocoons that camouflage and protect the fragile pupae. Cecropia caterpillars bind their cocoons to tree branches. Polyphemus caterpillars wrap leaves around their cocoons for extra camouflage. Luna caterpillars let their cocoons drop from trees, so they’re buried beneath a blanket of leaves.
Love is in the Air
If silk moth caterpillars are all about eating, then silk moth adults are all about romance. When silk moths emerge from their cocoons or burrows, they lack mouths and can’t eat. The only thing fueling their flutter is fat they put on as caterpillars. Once they burn through that fat, they die.
Because time is short, female moths speed courtship along by releasing pheromones (fair-oh-mones). Pheromones are like perfumes that male moths find irresistible. Males use their feathery antennae to follow pheromones to females. Each kind of silk moth releases pheromones at a certain time of night. This “calling time” keeps moths with similar-smelling pheromones from attracting the wrong mates.
Male moths mate one to three times but rarely live longer than two weeks. Females usually die once their eggs are laid. But about 10 days after adult moths fold their wings forever, an army of tiny but very hungry caterpillars hatch and begin inching their way toward becoming giants of the night.