Moths - Prairie Rivers of Iowa

Inch Your Way to Loving Worms!

by Jessica Butters | Feb 8, 2024

The pretty cecropia moth caterpillar!

We won’t be talking about love or flowers this Valentine’s Day, but we will talk about some love-able critters that can eat flowers! They’re squishy, fluffy, or prickly, and sometimes called worms. They can be striped, spotted, or elaborately camouflaged. They are mini bird burritos, have secret appendages, and can trigger gag reflexes. They will become tomorrow’s moths and butterflies. We’re talking about CATERPILLARS!

What exactly is a caterpillar?

These curious creatures are the larval stage of growth in butterflies and moths. The term “caterpillar” is colloquial, and almost exclusively refers to moths and butterflies (although some moth caterpillars are also called “worms” or “inchworms”). Other insects have different terms for their larval stages, such as “maggots” for fly larvae and “grubs” for beetle larvae.

Most people know that the caterpillar/larval stage is one step in the development process called metamorphosis. But did you know that there are two general kinds of metamorphosis: “complete” and “incomplete”? The big difference between the two is that insects using complete metamorphosis go through a pupal stage (a period where they are inactive for a bit). Butterflies and moths go through complete metamorphosis because a caterpillar forms into a pupa when it develops into a chrysalis or rests inside a cocoon. Insects that go through incomplete metamorphosis do not go through a pupal stage (some examples include dragonflies, praying mantids, and crickets).

A black swallowtail caterpillar with beautiful warning stripes that say “don’t eat me”.

Why so squishy?

Back to caterpillars: why would any animal want to be small, slow, and squishy for a period of their life? What is the advantage, considering how tasty caterpillars are to birds, rodents, and many other animals? About 80% of insects (including bees, ants, fireflies, and more!) use complete metamorphosis to grow, which requires this vulnerable phase. Why is this?

Besides the pupal stage, another hallmark of complete metamorphosis is that the larval stage and adult stage have virtually nothing in common. Most scientists agree that this difference is key to the success of complete metamorphosis: young and adult insects don’t have to compete for the same resources. Caterpillars munch on leaves and grow in vegetation while moths and butterflies sip nectar and fly around looking for mates. But what about the fact that most caterpillars are specialists? Why would caterpillars evolve to be picky?

The brightly colored cloudless sulphur caterpillar!

A red admiral caterpillar feeds on nettles in Brookside Park!

Why so picky?

To name two examples, monarch caterpillars can only eat milkweed, and red admiral caterpillars will only eat nettles. Wouldn’t it be much more advantageous to be able to eat any kind of plant, or at least a more general group of plants? Not necessarily. Specialist caterpillars seem to have better defenses against predation than generalist caterpillars: monarch caterpillars eat poisonous milkweed plants, and red admiral caterpillars hang out in nettles that sting – most animals will learn to avoid these caterpillars. Scientists also think that specialist caterpillars are better at identifying and choosing plants, and consequently eat more. Because so many caterpillars are specialists, it is imperative to plant as many native plants as possible if you want to help butterflies and moths. It’s surprisingly beneficial to be a picky, squishy caterpillar, but it’s still a dangerous world.

Worm weapons!

Plants can’t supply all necessary defenses – many caterpillars must deploy their own wacky weapons to defend their soft, protein-filled bodies. One tactic is coloration. Caterpillars can be camouflaged to look just like bird poop, or have colorful patterns to warn their predators they are poisonous or bad-tasting. Eastern tiger swallowtail caterpillars look almost exactly like miniature snakes, frightening off birds with their life-like eye spots. These caterpillars also have secret appendages, called osmeteria, that they strike out of their head to mimic a snake’s tongue! Other swallowtail species also have colorful osmeteria they can stick out in conjunction with nasty smells and sometimes irritating secretions (not harmful to humans). Other caterpillars take defense to new lengths: fecal firing.

You read that right. To help hide their smell from parasitic wasps, silver-spotted skipper caterpillars catapult their smelly frass (excrement) 38 body lengths away, a distance equivalent to 228 feet for a six-foot human! Curiouser still, some caterpillars like the walnut sphinx moth can squeak or whistle. The whistle sounds like a bird warning call, causing the hungry bird to drop the caterpillar. But let’s get into some hairier defenses.

A snake-mimicking eastern tiger swallowtail, with its osmeterium acting like a snake’s tongue!

Many caterpillars are hairy enough to make some 1980s bands jealous. Sometimes the fluff just means the caterpillars are cute; other times it means they shouldn’t be touched. Many fuzzy caterpillars can have hairs that break on contact, causing irritation on the finger or mouth that touched them. This doesn’t always affect humans; if you’ve handled woolly bear caterpillars before, you’ve handled these kinds of irritating hairs. Other caterpillars can have more irritating hair, or have specialized hairs that can actually deliver mild venoms. Puss caterpillars get a lot of media attention for the sometimes blistering results they can give to human skin, however there have been no sightings of these caterpillars in Iowa (puss caterpillars grow into a particular species of flannel moth). The buck moth and some slug and saddleback moth caterpillars can cause serious irritation, but sightings and encounters are very rare in central Iowa and symptoms normally do not need medical attention (for specifics on venomous caterpillars, read here). Most fuzzy caterpillars in Iowa are harmless or merely have irritating hairs. Removing hairs with tape, washing the area afterwards, and ice or baking soda paste is the best care for minor rashes from caterpillar hairs.

Pictures: Above, a touch-friendly woolly bear caterpillar. Below, a slug caterpillar that may irritate the skin. While not seen often in Iowa, some slug caterpillars can deliver more of a sting. Besides that, they look SO STRANGE! In nature they look like a spider’s shed exoskeleton, and are well-camoflaged in leaf debris. Read more here!

The last caterpillar defense tactic is one that we hope you aren’t dealing with this Valentine’s Day: manipulation. Some caterpillars can trick animals that are usually predators into being their caretakers! Many gossamer-winged butterflies (a family of butterflies comprised of hairstreaks, blues, coppers, etc.) exude pheromones as larvae that trick ants into thinking the caterpillar is a fellow ant. Some of these dainty blue butterflies use this trick to commit social parasitism! Exactly how they utilize ants varies for each species of this butterfly family; for today we will focus on Edward’s hairstreak, a species of special concern in Iowa. This species of butterfly munches oak leaves as a caterpillar, and utilizes mini shelters created by ants. As a young caterpillar, it stays in the trees. But as it grows older, the Edward’s hairstreak caterpillar eats in trees only during the night; as dawn approaches it drops to the base of the tree to hide in ant-made shelters called byres, which are small piles of thatch created from leaves, sticks, and other forest floor materials. The caterpillars secrete a honeydew as a reward for the shelter and protection the ants provide. This relationship is much more in the spirit of the holiday, giving us a loving mutualism rather than parasitism.

Above, an inchworm on my kale plants this year. Below, a monarch caterpillar that could be harmed by garden pesticides!

From beautiful colors to shooting feces and feeding ants, caterpillars are worthy of love and appreciation! To support this wonderful world of worms, be sure to plant a variety of native plants in your yard, and most importantly do not spray pesticides! Yes, many caterpillars will chew on your garden plant leaves. I suggest allowing a part of your garden to become a “nursery”, a subset of plants that you don’t mind getting eaten by caterpillars. You can “babysit” the caterpillars by moving them off the plants you care about and place them onto the plants in the nursery (using gloves if they are fuzzy). By not spraying pesticides and allowing caterpillars to stay in the garden, you win the fun of watching the caterpillars that ate your dill and carrots turn into black swallowtails! Keeping from spraying pesticides also allows you to enjoy bumble bees visiting your tomato plants and bees sleeping in your flowers. By tolerating the presence of insects and a few munched leaves, you can support an entire little ecosystem with your garden, and witness all the drama the insect world has to offer while pulling weeds and watering plants. Let the backyard garden be your gateway to the curious world of caterpillars!

Visit the following links to dive even deeper into the curious world of caterpillars!

– A list of butterfly/caterpillar host plants: https://henderson.ces.ncsu.edu/2021/05/plants-that-host-butterfly-larvae/

– More information on the importance of caterpillars: https://extension.psu.edu/a-case-for-caterpillars

– A fun read on caterpillars in the US: https://www.newyorker.com/magazine/2023/03/20/the-little-known-world-of-caterpillars

– More on metamorphosis: https://www.scientificamerican.com/article/insect-metamorphosis-evolution/

– More on ant-butterfly relationships: https://sites.tufts.edu/pollinators/2019/07/the-butterflies-who-are-raised-by-ants/

The Love Lives of Moths: Competition in the Air

by Jessica Butters | Feb 6, 2023

Forget about buying roses – in the great words of Shania Twain, “that don’t impress me much”. To impress me, you’d have to match the energy of male moths. Instead of dropping cash on last-minute flowers, male moths are willing to fly miles for a first date, dodge dangerous predators, and out-compete other males, all while most humans are fast asleep.

But how exactly do moths find each other? Many are nocturnal, some aren’t brightly colored, and they can be tiny*. Plus, female moths generally stay put and let the males come to them. So what is the male moth’s secret to finding love in the black abyss of a night sky? The key is their incredible sense of “smell” through their unique antennae!

If you’re looking at a moth, the antennae may tell you if it’s a male or a female. Female moths often have the two simple strands of antennae that we are used to seeing on many insects. It’s the male antennae that are interesting; some, though not all, have antennae that look like a pair of feathers, each one having many branches covered in fine hairs. These feather-like antennae quite literally comb the night air in search of the calls of female moths, which are sent in the form of pheromones**. Male moths from larger moth families (e.g. giant silk moths) can detect a single molecule of female pheromone from seven miles away! Imagine if you could find a compatible stranger based on smell alone, or attract one using a drop of perfume. Though odd, it seems simpler than using dating apps; but is it truly easier?

Distance isn’t the only threat to a male moth striving to be lucky in love. Once his antennae detect a female call of his species, he has to find her – fast. Other males may have picked up the female’s call as well, and many female moths only mate with the first male she encounters. There is no prize for second place. To hone in on her location, males often fly in the cross-winds to try to detect more pheromone. Once a call is detected, he flies in that direction until the pheromone fades yet again.

During this high-stakes game of Marco Polo, moths also have to dodge hungry predators, such as bats. Different moths have different strategies for this. They may taste bad so they are spit out instead of eaten, have evasive flight maneuvers that would impress any Top Gun fan, or have incredibly fuzzy bodies that absorb sound. This weakens a bat’s attempt to use echolocation, giving the moths a cloak of invisibility.

A moth’s antenna seen through a microscope. Note that it is covered in fine hairs!

While the journey to mate may be arduous for males, female moths have their own complex decisions to make. Female moths only release small amounts of pheromones in hopes of attracting male moths with very sensitive antennae, which indicates they are fit and healthy. Additionally, she only mates with the first male to find her to ensure he is a strong and fast flier, another indicator of good health. Female moths don’t have genetic material to waste on mediocre males – they put high amounts of energy into creating their eggs. However, if the mating period goes on and the female hasn’t attracted a mate, she will start releasing higher amounts of pheromone. This intensifies her call, making her easier to find. Besides intensifying her call, the female can also tailor when and how often she calls. These strategies help ensure that she receives the best male possible and that her energies were not spent in vain.

The world of moths remains a mystery to most people. Considering the intricacies and drama involved, it deserves to be a topic of regular discussion! If you are at a loss of what to talk about at your next Valentine’s Day date or gathering, consider bringing up moth mating. It’s sure to add interest to an otherwise trite Tuesday.

*Some moths are diurnal (active during the day), many are brightly colored, and some species are huge!

**Pheromones are chemicals released by animals that change the behavior of other animals of the same species.

The Incredible Diversity of Iowa Moths and Butterflies

by Jessica Butters | Jun 29, 2022

Did you know that National Moth Week is celebrated in July? Read up on Iowa’s native moths and butterflies to be ready to celebrate Moth Week right, from July 23rd to 31st!

Iowa is home to about 110 butterfly species, and over 2,000 moth species! Butterflies and moths are related: both are in the insect order Lepidoptera, which roughly translates to “scaled wing”. Most of us think of moths as the ugly stepsisters of butterflies, but this is not true! In fact, I would call moths the sleeping beauties of our natural world (they are beauties that are often active while we sleep). Don’t continue to sleep on the incredible beauty of Iowa moths, and get to know our butterflies better!

Giant Silk Moths
If you’re lucky enough to have seen a luna moth, then you’ve seen a member of the giant silk moth group, called the Saturniidae family (Saturnia is the daughter of Saturn in Greek mythology). This group also includes the cecropia moth, named after Cecrops, a half-man-half-snake king in Greek mythology. If you squint at the top outer corner of the cecropia moth’s front wing by the dark eyespot, you can see what appears to be a profile of a snake’s head. Lastly, the luna and cecropia moths don’t eat as adults – they have no mouths! They only eat as caterpillars, which is common in the mysterious world of moths.

Hawk Moths and Hummingbird Moths
Aptly named, these moths look and fly like humming birds, hovering while drinking nectar with their straw-like mouths (called a proboscis). Some also mimic bumble bees, like the snowberry clearwing pictured on the right! Belonging to the family Sphingidae, these moths can be diurnal (day-active) or nocturnal (night-active). Some species don’t eat as adults. For those that do, they are important pollinators for prairie orchid and primrose species!

Owlet and Underwing Moths
Most of these moths are the experts of disguise, using drab colors on their front wings to blend in with bark and dead leaves. They are in the family Noctuidae, the largest family of moths in North America. Underwing moths, however, have a secret weapon: their back wings can have bright colors that hide under the front wings, and can be flashed to startle a predator during escape!

Tiger Moths
When wooly bear caterpillars mature, they are called tiger moths, also known as the family Erebidae. These moths can have bright colors decorated with geometric lines, consequently nicknamed “tiger” moths. I saw the tiger moth pictured here the last week of June at Ada Hayden park! This species of tiger moth is called the “reversed haploa moth” due to the fact that it has two color variations: either geometric lines on the front wings with plain white back wings, or the reverse: plain white front wings with geometric back wings.

Brush-footed Butterflies
The family Nymphalidae, commonly called the brush-footed group, is one of the most popular groups of butterflies with monarchs, regal fritillaries, and painted ladies included in its ranks. Why are they called brush-foots? Their front legs are very small, and kept close to their body (similar to t-rex dinosaurs in my opinion). These front legs aren’t used for walking and are basically reduced to little “brushes”.

Swallowtails
While one of the most entrancing butterflies, swallowtails are tough; they overwinter here in Iowa! As caterpillars, this group (which is the family Papilionidae) spin their chrysalises and wait out the winter under dead leaves, giving us another reason to leave areas in our yard undisturbed this fall. The caterpillars of this group can just as awe-inspiring, with some having bright green colors, or eyespots that can make them look like snakes to scare predators away!

Whites and Sulphurs
This group of butterflies has a charming behavior; they like puddles! Belonging to the Pieridae family, these butterflies are the most likely to be found in a “puddling” group, sucking up extra nutrients in the water. Adult butterflies appear white, yellow, orange, and sometimes have black markings. One of the coolest butterflies in this group is the Olympia marble, a species of special concern in Iowa due to declining numbers. Just look at its metallic markings against snow-white wings!

Blues, Coppers, and Hairstreaks
These tiny butterflies are also called gossamer wings, due to the beautiful shimmer that reflects off their wings! These butterflies are a part of the family Lycaenidae, and also love visiting puddles, so don’t let their looks fool you; they are hardcore. Continuing that thought: the species Satyrium edwardsii, or Edward’s hairstreak, has some wild behavior as a caterpillar. At night it feeds on oak leaves, and during the day it rests in active ant nests for protection! This species is also a species of special concern in Iowa due to declining numbers.

Skippers
If you can’t tell if an insect is a butterfly or a moth, you may be looking at a skipper. Skippers are in the family Hesperiidae, and have chunky bodies with hooked, hockey-stick-shaped antennae. They appear carefree as they skip through the air. From the side, their wings give them a triangular, shark-fin shape. Out of the two butterfly species in Iowa considered endangered, one is a skipper, called the Dakota skipper. It requires high-quality prairie remnants, a habitat extremely hard to find in Iowa.

While many people love butterflies, these insects don’t always receive the respect they deserve being diverse and important wildlife. They are more than nature’s gems-they are important pollinators that have fun behaviors to appreciate! Moths are often forgotten, despite the fact that they can be bigger and more colorful than many butterfly species, and have the coolest adaptations, such as flashes of color and mouth-less adults! The world of moths and butterflies is not just a pretty one; it’s a wild one!