Life of silkworm moth is short — and ever-changing.
A strikingly green caterpillar about as long as my little finger was attached to a sprig of oak leaves in our yard.
Knowing the caterpillar with spikes on its back was the larvae of an Io silkworm moth, we clipped off the twig along with extra oak sprigs for caterpillar food and placed it inside a ventilated container next to a window inside our house.
My wife, Kathy, brushed a finger against the caterpillar and got a sharp sting from the defensive venom in the critter’s spikes.
Moth caterpillars, aka larvae, continuously feast on the host plant where they were hatched from a tiny egg. They grow larger through about five successive instars, aka molts, wherein they shed outgrown skin in order to expand their size.
The fifth instar is the prelude to pupating, in which the caterpillar forms a hardened pupa called a cocoon. After a few weeks, or sometimes months, a seeming miracle unfolds as the once worm emerges as a dazzling creature sailing on tissue-thin wings.
Our green caterpillar is in its final instar and will soon spin a papery cocoon in leaf litter on the bottom of the container. The cocoon will harden in about 10 days.
After two to three weeks, an Io moth will break forth from the cocoon, in a process called eclosion, and flutter on brownish-purple forewings spanning more than 2-inches and hindwings varying from rusty-red to brownish and yellow while displaying big blackish-blue eyespots dotted white in the center, like otherworldly pupils.
We’ll release the moth outside where it will fly only at night, as do most moths. While at rest during the day, the eerie eyespots should scare away insect-eating birds.
The moth’s name comes from Greek mythology, where Zeus turned his human mistress Io into a white cow to conceal her from the jealous rage of his wife, Hera. Go figure.
Moths belong to insect order Lepidoptera, Greek for scaly winged. This is the same order as butterflies, but moths have threadlike antenna, whereas butterflies have clubbed antenna. North American moth species outnumber butterfly species by 11,000 to 765.
Io moths are relatively common in Houston, as
are other silkworm moths — like the elegantly longtailed, ghostly green luna moth, the multihued reddish-brown cecropia moth and the large yellowish-brown Polyphemus moth.
Cocoons have long been hibernating in leaf litter and soil but have recently been opening for the egress of abundant summer moths — just look at the wall by a nighttime porch light.
Silkworm moths have no functioning mouth parts for eating or drinking. They live a week or two solely to breed while females lay eggs the size of pinheads on host plants, promulgating a new generation of moths.