Moths

South Carolina is home to over 400 species of moths, a small sample of the almost 11,000 species found in the United States. Many are incredibly vibrant and eloquently patterned. Most people tend to think of butterflies as beautiful pollinators while simultaneously thinking of moths as drab pests. This is far from the truth. Moths are vital for a healthy ecosystem, providing food for small predators and contributing to overall biodiversity. While most frequently encountered moths are fairly nondescript, there are many strikingly patterned and colored species. Most moths are predominantly nocturnal, however some are diurnal such as the hawk moths (family Sphingidae), which are pollinators for many flowers. The hummingbird hawk moth earns its name by often being mistaken for a hummingbird feeding on flowers during the daytime. Closer observation will reveal its true identity.

Moths and butterflies are both in the taxonomic order Lepidoptera, but the two groups can be readily distinguished by their wings and antennae. Moths hold their wings horizontally, mostly in a fashion that covers their abdomens. Butterfly wings fold up vertically with the abdomen visible. Butterflies have long, smooth antennae whereas those of moth’s are feathery and fuzzy. Both start out as caterpillars, which are essentially chronic feed tubes. During the caterpillar stage butterflies and moths get most of their nutrients for the rest of their short-lived existence. Butterfly caterpillars form a hard chrysalis while moth caterpillars form silky cocoons to undergo metamorphosis. Inside their cocoon or chrysalis, tissue that originally formed the caterpillar starts to rearrange to form the head, body, wings, and legs. The metamorphosis process can be anywhere from 8-50 days depending on species and environmental conditions. As soon as they emerge, butterfly and moth wings are wet and curled up and must dry out and uncurl before the adult can take flight.

Large silk moths (family Saturniidae), like the luna and polyphemus moth, lack a digestive system in adult form and only live around a week. Their entire existence as a moth has one purpose, to reproduce. Female silk moths emit pheromones able to be picked up by males from great distances away with the aid of their large, feathery antennae. Luna moths have evolved a fascinating way to reduce predation in adult moths. They have long, distinctive “tails” on their hindwing that trail behind the moth as it flies. These tails work to deflect the echolocation of bats away from the body and wings and into the tails which are not vital for the moth’s survival. Oftentimes luna moths are found with broken and missing tail wings from misdirected bat attacks. Another species of silkmoth with an interesting defensive mechanism is the io moth. This vibrant yellow or peach-colored moth has large eye spots that can fool a predator into thinking it is a larger creature not to be messed with.

Other species use a large array of defensive strategies, many of which are during the caterpillar phase. The ornate bella moth’s host plant is rattlebox (Crotalaria), a plant that produces poisonous seeds. The beautiful orange and black caterpillar is immune to the poisons and can therefore feed on the seeds. This builds them a level of chemical protection, making the bella moth poisonous and distasteful. Many would-be predators, especially spiders and birds, learn their lesson once to a bella moth and are unlikely to attempt to try another. Among the most renowned caterpillar arsenals for defense are stinging hairs.

The painful sting of the saddleback caterpillar, a stunning green and brown caterpillar that sports four cactus-like extensions covered with venomous spines, leaves an unpleasant memory for anyone unlucky enough to brush against one. Some caterpillars fool predators simply by looking threatening. The bright green caterpillars of the regal moth are humongous, bearing large intimidating orange horns earning them the name hickory horned devil. Yet they are completely harmless. Unlike most moths, they burrow into the ground and form a naked pupa, eventually emerging as a remarkably brilliant orange and yellow regal moth.

The biodiversity of moths is more difficult to observe easily without special methods than many other insects due to their elusive and primarily nocturnal behavior. One way to attract and admire moths is to string up a moth sheet. The technique is as simple as hanging a white bedsheet near a light (ideally a UV light for best results, but a floodlight from a house works just fine) in an otherwise dark area. Along with beetles and many other insects, moths are positively phototactic, meaning they are attracted to lights, for reasons currently unknown to science. Checking the sheet every 20-30 minutes will often reveal much of the hidden biodiversity around. Otherwise, a whole lot of moths may be living right in your backyard without you ever knowing they are there.