Moths fly under the radar. Less showy than butterflies, their close relatives, and less visible as so many are nocturnal, we tend to focus on the damage they cause (a hole in a favorite sweater, for example) rather than the important role they play in maintaining a healthy ecosystem. Moths pollinate night-flowering plants, are an important food source for birds and bats, and provide us with silk, one of our finest fabrics. Gypsy moths harm trees, but the caterpillars provide food for nesting birds and their droppings serve as fertilizer, helping to revitalize the forest.

Let’s take a closer look at moths, their complex and adaptable wings, their many disguises, and their unexpected superpowers. Let’s explore their different life stages that give moths the ability to specialize and adapt their form to meet their needs at each stage of their development.

Multipurpose Wings

White-lined sphinx moths, with heavy bodies and relatively short wings, have to beat their wings very fast, causing them to resemble hummingbirds as they hover over a flower to sip its nectar. However, sphinx moths’ streamlined bodies and narrow wings also make them fast and agile. They can quickly dart away from an attack or briefly fly backwards.

The tiny scales (modified hairs) covering moths’ wings lend themselves to an astonishing variety of colours and patterns, providing both camouflage and warning displays. The scales detach easily if a moth is caught in a spider’s web. They also absorb bat sonar making them less noticeable to bats, one of their key predators.

In addition to flight, moths use their wings to regulate their body temperature. The scales on their wings, like tiles on a roof, provide insulation. They ‘shiver’ in order to raise the temperature of their flight muscles when it’s cold, and they’re able to transfer heat from one part of their body to another.

Masters of Disguise

The polyphemus silk moth can be found in all four western provinces. They have large purplish eyespots on their hindwings that are designed to startle and distract potential predators.

Moths employ several tactics to avoid predators. Some use camouflage to blend in with their surroundings. Dull colours and mottled patterns are a perfect match with bark or lichen when a moth is resting on a tree. Moths may even adapt their shape to resemble a twig or a dead leaf. Others try to warn off predators by resembling wasps or bird poop or by having extremely lifelike eyespots on their wings that intimidate pursuers. Eyespots may also deflect an attack as the predators aim for the eyespots located at the edge of the wings, providing the moth with a greater chance of survival. Birds are less likely to eat caterpillars such as the spotted tussock moth caterpillar as they are covered in stiff bristles.

Unexpected Superpowers: Taste, Smell, and Sound

Spurge hawk moths were introduced into Canada to help control weed spurges. They have a modified mouthpart that enables them to detect the sonar cries of bats, a useful skill for a night-flying insect.

Moths have some of the most sensitive hearing in the insect world, enabling them to detect the high-pitched cries of bats, one of their primary predators. Moths’ ‘ears’ can be found on various parts of their body but are usually located near the wings where they can quickly alert the moth to move towards or away from a sound.

Many moths are nocturnal and rely on their well-developed sense of smell to find each other. The cecropia silk moth is North America’s largest native moth. The female emits pheromones to attract a mate, which the male’s sensitive antennae can detect from a distance of up to 1.5 km. Moth antennae are often feathered, providing a larger surface area of sensory receptors.

The earliest moths probably chewed plants to obtain nourishment. The development of a proboscis, a long straw-like mouthpart, was a game-changer as it permitted them to suck up nectar and other plant juices. When not in use, the proboscis is tightly coiled up inside its mouthpart. The proboscis of a hawk/sphinx moth can be up to 36 cm long, and yet they manage to insert it into a tiny opening to obtain nectar: “‘It's like trying to hit the opening of a drink can with a two metres long straw in your mouth,’ says Anna Stockl, part of a research team into how moths control their proboscis.” They discovered that moths use visual feedback to position their proboscis, moving their body and their proboscis to arrive at their goal.

Moths have a few taste buds on their proboscis and antennae, but most are located on their feet in the form of scales, bristles, and pits so the moths can taste the plant they’ve landed on.

Life Stages

The larvae of one-eyed sphinx moths feed on willow and poplar, while the adults are unable to eat as they haven’t got a functional mouth part.

Butterflies and moths progress through four life stages: egg, larva (caterpillar), pupa (cocoon), and adult (wings). They moult between each of these stages as their bodysuit will only stretch so far. Most moths moult 4 or 5 times, but for some it’s many more. They’re very vulnerable and unable to move while moulting until their new skin hardens.

Moths dramatically change their appearance between each of the major life stages in order to equip them with the necessary body parts and senses. Caterpillars grow rapidly and require lots of food, so they have well-developed mouthparts. On the other hand, their eyes are simple as they won’t be needed for complex tasks. Unlike adults, the larvae have elaborate silk glands and a spinneret for extruding silk when it’s time to spin a cocoon. The eggs are usually laid in batches for better thermoregulation; there is safety in numbers; and they’re able to fully take advantage of a food source.

Further Information

Moths: A Complete Guide to Biology and Behavior, David Lees & Alberto Zilli [Smithsonian]

For the Love of Moths [Xerces Society]

Lives of Moths [Butterfly Conservation]

10 Things You Didn’t Know About Moths [National Geographic]

Six Unexpected Pollinators [EcoFriendly West]

Nature Companion, a free app/website introducing many of the plants and animals found in Canada’s four western provinces [EcoFriendly West]

Photo credit: One-eyed Sphinx Moth https://www.flickr.com/photos/apmckinlay/42992650941

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