Inch Your Way to Loving Worms!

Inch Your Way to Loving Worms!

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?

A lucky four-leaf clover.

The brightly colored cloudless sulphur caterpillar!

Luna Moth

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/

Trees for the Bees: How to Support Wildlife this Arbor Day!

Trees for the Bees: How to Support Wildlife this Arbor Day!

A native bee visiting a redbud tree.

These warmer days make it hard to sit still; we all want to get a jump on our yard and garden plans! Maybe you’re thinking of adding some small pockets of pollinator habitat. Or perhaps you’ve finally decided to add a tree or two for shade. While there’s a dizzying number of guides for “pollinator flowers”, there’s less advice on how homeowners can utilize trees and shrubs to support wildlife.

Planting a tree can be an investment not only of money but of time as well. When thinking about the long-term goals for your property, it’s important to think about the legacy you want to leave behind, as the tree may outlive you. Planting the right trees can not only increase your property’s appeal; it can also provide habitat for songbirds and pollinators for decades to come! So which trees are attractive to pollinators, are native to Iowa, and look great in our yards? We’ve put together a list to answer some of these questions, just in time for Arbor Day, which falls on April 28 this year!

But first: why trees?

Native trees and shrubs provide excellent wildlife habitat in several ways. Many provide an early flower source for pollinators such as bees and butterflies, and they are also great habitat for birds! Trees provide nesting and hiding areas for birds, and can attract insects that birds need to feed their chicks (more on that later). Planting native trees will especially invite butterflies and moths to visit your yard and lay their eggs, which hatch into caterpillars. These caterpillars then snack on tree and shrub leaves (they won’t do any real damage) until they spin their chrysalises or get plucked by a bird. Caterpillars and other insects are fundamental to the food web: they are the juicy, protein-filled link between plants and larger animals. If you want to see beautiful butterflies and songbirds, you should plant native trees that support native insects!

A blue jay with an acorn.

Native trees are central to an exciting, diverse yard!

The nonnative ginko tree (the one with fan-shaped leaves) supports about 4 species of caterpillars. In contrast, native oak trees alone can support 534 species of caterpillars (according to Dr. Doug Tallamy*). Consider the fact that black-capped chickadees need at least 300 caterpillars a day to feed their chicks – that’s about 5,000 caterpillars needed in a few weeks while the chicks grow! And this is just one example. Imagine if you had three chickadee families in your yard, or five other species of birds visiting your feeders. Suddenly, native trees just seem practical, and planting nonnative trees, such as a ginko, seems, as Tallamy put it, “equivalent to erecting a statue” in terms of its usefulness.

A young chickadee and parent.

Unhelpful trees:

Let’s address the elephant in the room: some trees and shrubs commonly planted in yards are pretty damaging; they easily spread from our yards and choke out native plants that wildlife depend upon, and cost cities and counties thousands of dollars to remove from natural areas and building foundations (some of these trees’ roots can actually compromise the integrity of buildings). Some trees and shrubs to stay away from include: Bradford or Callery pear trees (Pyrus calleryana; also their flowers smell bad), Norway maples (Acer platanoides), buckthorn (Frangula species), multiflora rose (Rosa multiflora), tree of heaven (Ailanthus altissima), and Amur and Morrow’s honeysuckle (Lonicera maackii and L. morrowii, respectfully).

 

 

Lastly, do your best to avoid planting cultivars and hybrids that promise better color, bigger flowers, etc. Most native trees (especially maples) produce spectacular fall color anyway, and the hybrids you see in the nurseries will likely be sterile, and won’t produce flowers that attract pollinators or birds (if they produce any at all). It is also important to note that nonnative shrubs, trees, and hybrids may tout that they produce berries, and therefore support wildlife. Birds in particular may feed on berries only certain times of the year, and that time may not coincide with berry production on hybrid plants. Additionally, these nonnative plants will not come close to supporting the number of caterpillars needed to keep birds nesting in or near your yard.

Bradford pear tree with smelly flowers.

Multiflora rose choking out trees.

Now for the main event: the best shrubs and trees to plant!

How the lists are set up: Shrubs, small trees, and larger trees that are native to Iowa and beneficial to pollinators are listed below in order of bloom time. Each table describes a specific genus or species of tree, which is pictured to the right of the table (or below in mobile format).

Shrubs and small trees are listed first, and larger trees are listed afterwards. A small picture of the blooms produced by a shrub or tree may be displayed in the corner of the picture of the mature plant. These are not exhaustive lists; they are meant to get you started!

{ See end of article for a list of places to purchase native shrubs and trees! }

Shrubs

 

The following native plant species are shrubs and small trees reaching a maximum height of 30 feet. These trees are perfect for small yards, or large yards that want to add visual interest and diversity by planting trees of varying heights. Some of these shrubs also make great hedges or borders near property lines! Be sure to look up how some of these shrubs spread to make sure their maintenance needs meet your expecations.

Common NameBloom PeriodSun and Soil Needs
Pussy WillowEarly to Mid-SpringFull Sun, Wet – Moist
Species NameBloom LengthWildlife Supported
Salix discolor2 WeeksPollinators, Birds
Max HeightBloom DescriptionFall Color
6 – 20 ftSmall, fluffy white catkinsDull green – yellow

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
Serviceberry (Juneberry)Mid-SpringPart – Full Sun, Moist – Dry
Species NameBloom LengthWildlife Supported
Amelanchier arborea1 – 2 WeeksPollinators, Birds, and more
Max HeightBloom DescriptionFall Color
6 – 20 ftWhite, 1-inch flowersRed-orange

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
Eastern RedbudMid-SpringPart – Full Sun, Moist – Dry
Species NameBloom LengthWildlife Supported
Cercis canadensis4 WeeksPollinators
Max HeightBloom DescriptionFall Color
15 – 25 ftShowy pink flowersYellow

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
American PlumMid- to late SpringPart – Full Sun, Medium
Species NameBloom LengthWildlife Supported
Prunus americana2 WeeksPollinators, Mammals
Max HeightBloom DescriptionFall Color
10 – 15 ftShowy white flowersRed to Yellow

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
Prairie Crab AppleLate SpringPart – Full Sun,  Moist – Medium
Species NameBloom LengthWildlife Supported
Malus ioensis1 – 2 WeeksPollinators, Birds, and more
Max HeightBloom DescriptionFall Color
10 – 25 ftShowy white-pink flowersBrown-orangeish

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
Gray DogwoodLate Spring to Mid-SummerPart – Full Sun,  Moist – Medium
Species NameBloom LengthWildlife Supported
Cornus racemosa3 WeeksPollinators, Birds, and more
Max HeightBloom DescriptionFall Color
8 – 15 ftShowy white flowersRed-purple

 

Butterfly weed
Common NameBloom PeriodSun and Soil Needs
American ElderberryLate Spring to Mid-SummerPart – Full Sun, Moist
Species NameBloom LengthWildlife Supported
Sambucus nigra canadensis, or Sambucus canadensis3 – 4 WeeksPollinators, Birds
Max HeightBloom DescriptionFall Color
4 – 12 ftShowy white flowersBrown-reddish to Yellow

 

Butterfly weed

Trees

 

The following species are taller native trees ranging from 40 to 120 feet tall. These trees will provide high-quality habitat in larger yards, and are sure to attract and support wildlife, especially if mutlitple species are planted. Be sure to check if these trees create any fruits or seed pods so you can determine which trees best match your expectations.

Common NameBloom Period Sun and Soil Needs
Maples (Sugar, Black, and others)Early to Late SpringPart – Full Sun, Medium
Species NameBloom LengthWildlife Supported 
Acer species1 – 2 WeeksPollinators, Birds,  and more
Max HeightBloom DescriptionFall Color
60 – 100 ftSmall yellow-green flowersStriking colors, varies by species
Bicknell's sedge

Sugar Maple (Acer saccharum)

Common NameBloom Period Sun and Soil Needs
Black CherryLate Spring to Early SummerPart – Full Sun,    Moist – Dry
Species NameBloom LengthWildlife Supported 
Prunus serotina2 – 3 WeeksPollinators, Birds,  and more
Max HeightBloom DescriptionFall Color
50 – 80 ftShowy white flowersYellow to reddish
Bicknell's sedge
Common NameBloom Period Sun and Soil Needs
Kentucky CoffeetreeLate Spring to Early SummerPart – Full Sun,    Moist – Medium
Species NameBloom LengthWildlife Supported 
Gymnocladus dioicus2 – 3 WeeksPollinators, Birds
Max HeightBloom DescriptionFall Color
60 – 90 ftSmall white flowersYellow
Bicknell's sedge
Common NameBloom Period Sun and Soil Needs
Basswood (Linden)Early SummerPart – Full Sun,    Medium
Species NameBloom LengthWildlife Supported 
Tilia americana2 WeeksPollinators
Max HeightBloom DescriptionFall Color
50 – 100 ftSmall white flowersDull green – yellow
Bicknell's sedge
Common NameBloom Period Sun and Soil Needs
Oaks (Red, White, and others)VariesVaries
Species NameBloom LengthWildlife Supported 
Quercus speciesVariesInvaluable to countless wildlife
Max HeightBloom DescriptionFall Color
40 – 80 ftVariesDull to striking colors
Bicknell's sedge

Northern Red Oak (Quercus rubra)

* = According to research by Dr. Doug Tallamy, author and faculty member at the University of Delaware.\

This article used a number of resources, including:

Ladybird Johnson Wildflower Center                                      Michigan Department of Natural Resources

Missouri Botanical Garden                                                         Michigan State University

University of Minnesota Extension                                            USDA NRCS PLANTS Database

 

Some great native shrub and tree nurseries:

 

The State Forest Nursery: Ames, Iowa.  1-800-865-2477 or 515-233-1161

Iowa Native Trees and Shrubs: Woodward, Iowa. 515-664-8633

Blooming Prairie Nursery: Carlisle, Iowa. 515-689-9444

Happy Arbor Day, and happy tree planting!