Caterpillar Host Plants: Harvesting Solar Energy for Wildlife

Plants feed wildlife. Plants feed nearly all life as we know it.  They are the base of the food web and produced much of the oxygen in the atmosphere:  Calories to consume and the fuel to burn them.  Even those creatures that consume other animals are dependent upon plants for their survival.  The solar energy that plants convert to sugars and the minerals that they mine from the soil slowly make their way up the “food chain” to even the most carnivorous apex predators via the bodies of their herbivorous prey.   The somewhat outdated concept of the “food chain” can still help to visualize the process of nutrients and energy cycling through natural communities.  These days it is most often referred to as a “food web” and the following graphic is a simplified representation of how it functions with some familiar examples.

food_web

(There should be more arrows going all over the place, a ‘web’ if you will, but like I said, this is simplified to highlight the cyclical nature of the whole process.)

The main points of this graphic I want to focus on are 1) Energy comes from the sun.  2) That energy is harnessed and stored as carbohydrates by plants.  3) The rest of the system depends upon harvesting that stored energy.  Everything else is standing on that foundation of plants

As omnivores, humans have the ability to derive our energy from many sources, and in fact need a varied diet to acquire all of the nutrients necessary for our bodies to function.  It allows us to occupy nearly any area on the planet, but other creatures are not so easily adaptable to new foods and environments.  Survival strategies are often dependent on the seasonal abundance of plant resources with periods of migration or hibernation to cope with food scarcity.  Many insects have evolved to become specialists at feeding on certain types of plants in response to the annual growth cycles in temperate climates.  Typically, an egg is laid on or in a preferred food source, a larva emerges and feeds on that food source until it consumes enough energy to pupate into a winged adult.  The adult then flies off to find a mate, locate another larval food source, lay egg(s), and repeat, if possible, until they die.  Aphids, Wasps, Bees, Moths, Butterflies, Flies, and Beetles all follow this same basic life cycle.

IMG_6108

Black Swallowtail laying eggs on Meadow Parsnip (Thaspium trifolatum)

Butterflies and Moths, collectively known as Lepidoptera, have adapted specialized strategies to feed on plants and mitigate the effects of their defenses in an evolutionary tango over the past 60-100 million years. Through the process of evolution and adaptation the insect’s fate has been inextricably tied to the fate of the plants they consume.  Lepidopteran larvae, commonly referred to as: caterpillars, grubs, tentworms, silkworms, inchworms, armyworms, etc. are a crucial first step in transferring the sun’s energy throughout the ecosystem.  A feature of their specialized feeding behavior is that they have become much more efficient at converting the plant material into proteins with which they build their bodies.  Those proteins are the main food source for many of the creatures that occupy the next trophic level up the pyramid.

Enigmogramma basigera (Pink-washed Looper Moth)

Freshly emerged Pink-Washed Looper Moth (Enigmogramma basigera) and it’s cocoon on a Cardinal Flower (Lobelia cardinalis). Many of it’s larval siblings were dinner for baby birds.

One of my favorite sources for information on butterflies, moths and caterpillars is BAMONA (Butterflies and Moths of North America), a website/database operated by the Butterfly and Moth Information Network.  It has tons of information and resources for anyone looking to learn more or contribute their knowledge and sightings of Lepidopterans.  I spent a little while browsing their database of species and compiled the following list of common names for Butterflies and Moths. See if you can spot the pattern:

“Elder Shoot Borer Moth, Maple Leaftier, Small Aspen Leaftier Moth, Black-headed Birch Leaffolder Moth, Oak Leaftier Moth, Poplar Carpenterworm Moth, Birch Tubemaker Moth, Pecan Leaf Casebearer Moth, Alder Tubemaker Moth, Birch Dagger Moth, Cottonwood Dagger Moth, Tupelo Leaffolder, Fringe-Tree Sallow, Knapweed Root-borer Moth, Poison Hemlock Moth, Virginia Creeper Borer Moth, Fall Clematis Clearwing Borer, Seagrape Spanworm Moth, Walnut sphinx, Poplar Catkin Moth, Yellow Birch Leaffolder Moth, Consular oakworm moth, Oslar’s oakworm moth, Peigler’s oakworm moth, Orange-tipped oakworm moth, Spiny oakworm moth, Pink-striped oakworm moth, Orange-striped oakworm moth, Chestnut Crescent, Live Oak Antiblemma, Oblong Sedge Borer Moth, Large Boxelder Leafroller Moth, Spring Spruce Needle Moth, Fall Spruce Needle Moth, Cherry Shoot Borer, Hickory Leafroller Moth, Hackberry Emperor, Ten-spotted Honeysuckle Moth, Wavy Chestnut Moth”

(These are just a sampling of the species whose Latin names begin with the letter ‘A’!)

The pattern to which I was referring is that the plant that the larva feeds upon is right there in the adult’s name.  Many even tell you the plant part they consume: Leafroller, Shoot Borer, Root Borer, Poplar Catkin, Spruce Needle, etc.   Being a specialist at consuming such specific plants and plant parts confers the advantage of less competition for food resources, but it is a double edged sword.  If that particular plant or part of the plant is not available then the caterpillars cannot survive.   This is where you, the human, enter the picture.  Many of the native plants that were interwoven into the landscape and served their purpose as a larval food source for millennia have been marginalized or removed altogether.  First, agriculture, next urbanization and development, and then landscapers all took turns removing the native smorgasbord and replacing it with foreign, undigestible plants.  Whereas a human might view a Chinese Cherry tree ringed with a border of Monkeygrass surrounded by a freshly mown lawn as a tidy, beautiful landscape, a butterfly looking for a place to feed and nurture her young might see a desert or a wasteland devoid of food.  That same human would probably derive a very similar aesthetic pleasure from an American Cherry Tree ringed with sedges and surrounded by native bunchgrasses, and over 500 species of Lepidoptera would see food and a nursery for the next generation.

Spring is nearly upon us.  That time of year when everyone briefly turns their attention to beautifying their yards before it gets too hot.  Beware the big box stores and their clone armies of gold medal winning plants injected with systemic insecticides.  “Pest Free” is another way of saying “Useless to Wildlife.”  Resist the impulse buy in the garden center.  Do your research and find some plants that will satisfy your aesthetic wants AND wildlife nutritional needs.

blackswallowtails

Black Swallowtail caterpillars on Meadow Parsnip (Thaspium trifoliatum). The plants responded with lush new growth a week later.

 

Postscript:

In the course of researching moths for this article I stumbled upon an account of a moth with a truly unique larval food source: The Gopher Tortoise Moth (Ceratophaga vicinella).  Based on the naming conventions described above what would you guess that Gopher Tortoise Moth caterpillars eat?  If you guessed Gopher Tortoise Shells you would be correct!  More specifically they consume the solid keratin that binds the many plates of a gopher tortoise shell together.  Keratin is the same protein found in your hair and fingernails and other natural fibers such as wool.  The ability to digest and derive sustenance from keratin is shared by a close cousin of the Gopher Tortoise Moth: the common Clothes Moth that loves to eat (you guessed it!) wool clothing and rugs.  The amazing part of this relationship to me is that there used to be such a surplus of Gopher Tortoise shells laying around that their abundance encouraged an entire new species to branch off and specialize in consuming only tortoise shell keratin.  Sadly, this strategy has proven to be risky with the decline of Gopher Tortoises, which is a direct result of the decline of the Longleaf Pine-Wiregrass ecosystem (and its seasonal fires) on which they are dependent.   There are hundreds of other animals and insects that depend on Gopher Tortoises and their burrows in some form to survive, and none of them are doing well.  Bring back the Longleaf!

 


Lauraceae: Sassafras, Guacamole, Cinnamon and other tough spells

IMG_4120a

Sassafras albidum leaves are variable.  This 3-lobed shape is most recognizable.

Laura who?  Lauraceae is a plant family.  Just in case you’re a little hazy on what that means… Most of us are familiar with the hierarchy we had to memorize in High School Biology class: Kingdom-Phylum-Class-Order-Family-Genus-Species.  Some of the categories can be further subdivided, such as the ‘Family’ level, which can be divided into ‘Subfamilies,’ and some of these are even subdivided into ‘Tribes.’ The Latin names we use for plants on this site and our plant tags are just the Genus and Species, but the actual full scientific name would have at least seven words! When I type “Liatris spicata” (Blazing Star) that is actually shorthand for “Plantae Angiospermophyta Dicotyledoneae Asterales Asteraceae Liatris spicata.”  So, when I say something is a plant family, I’m referring to that third step up the taxonomy ladder that ends with the suffix “-aceae.”  Some plant families you might be familiar with are Asteraceae (Sunflowers, Coneflowers), Lamiaceae (Mints), Rosaceae (Roses, Apple Trees, Strawberries), Solanaceae (Tomatoes, Peppers, Eggplant, Tobacco) and Violaceae (Violets).  The members of a plant family all share some common characteristics that were most likely inherited from a common ancestor.  Recent advances in DNA analysis have lead to some minor and major regroupings in plant families, with many new genera and species created as the picture of how plants evolved has become clearer. IMG_3083a

Spicebush (Lindera bezoin) flowers bloom in late winter/early spring before the leaves sprout. 

Lauraceae is a medium sized plant family with most of the members adapted to life in cloud forests near the equator.  South and Central America and Southeast Asia have the steep mountainous terrain and proximity to the Equatorial Pacific Ocean to produce cloudforests, and the majority of the species in the Lauraceae family reside there.  Nearly all of the members are trees or woody shrubs that contain essential oils.  Cinnnamon, Bay, Camphor, Avocado, Sassafras, and Spicebush are all in this family, and all have very distinct odors from the compounds in the oils they produce. The majority of this family also produce fleshy fruits with a single, relatively large, seed or pit in the center.  These fruits are attached to the branches by a bowl-shaped “cap” much like an acorn on an oak.IMG_4132a

Sassafras bark resembles that of a pine tree at first glance.

The last two on the above list, Sassafras (Sassafras albidum) and Spicebush (Lindera spp.) are Georgia natives and pretty unique for this family because they are deciduous.  Sassafras roots have long been used in tinctures as a treatment for all manner of ailments, and as a flavoring for root beer.  Spicebush leaves and twigs are used to make tea, and as a result of repotting many dozens of them I can tell you that their roots have a very pleasant aroma. Both Sassafras and Spicebush are dioecious, meaning that there are male and female plants, and both are required for the female plants to produce berries.  These berries are important food sources for birds, especially migratory ones.  The berries have a high fat content (think Avocados) and are great long-lasting fuel if you are flying to the other side of the planet.

IMG_2376

Spicebush Swallowtail caterpillar on Spicebush leaf.  Sassafras is also a host plant for these caterpillars.

One more fun fact about plant families: They often host specific families of butterfly and moth caterpillars.  These organisms have co-evolved in the arms race between plants and their insect predators.  Specific caterpillars adapt new ways of breaking down and deriving nutrients from the very oils and volatile compounds that the plants began producing as a means to repel hungry leaf-eaters. Many caterpillars actually incorporate the compounds into their flesh, also as a means of deterring predators!  Monarch caterpillars digest chemicals (cardiac glycosides) produced by milkweed that would stop the heart of most other animals.  Spicebush Swallowtail caterpillars consume leaves that would probably have a turpentine-like taste to you and me.  These relationships began many, many thousands of years ago, and continue to evolve to this day.

IMG_4135a

Sassafras tree turning brilliant colors between a dogwood and an oak.

You are now familiar with most of the local members of an entire plant family! Learning plant families is a great way to get a sense of the bigger picture of plant taxonomy.  I first read about it in the book “Botany in a Day” by Thomas J. Elphel, and I highly recommend it to anyone that wants to learn more about plants.  I still learn things every time I open it up, and I’ve had my copy for about 5 years.  CLICK HERE to go to Elphel’s website where you’ll find lots of web resources and the links to buy his book if you wish.

Sassafras trees are turning beautiful colors right now, so keep an eye out for those distinctive leaves.  I just “discovered” several trees around my neighborhood that I had never noticed before. Are there any on your street?sassafrasfall


Cullo-whee!

     Pandra and I had the pleasure of attending the 30th annual Cullowhee Native Plant Conference last week, and visions of host plants are still dancing in our heads.  Dozens of great speakers gave informative and inspiring talks on everything from seed saving to plant-fungus associations in the soil.  I’m going to try to relay some of the highlights and a small portion of the knowledge that these people passed to me.     IMG_20130719_093653_179  

      Doug Tallamy (above, with caterpillar slide) gave two talks at the conference, and they both focused on the importance of native plants as habitat for insects and birds.  His book, Bringing Nature Home is one of the most accessible books about ecology that I’ve ever read.  It’s been an inspiration to us, and I highly recommend reading it if you haven’t already. The central point is that plants are the source of all energy (via the sun), and in order to transfer that energy up the food chain to birds, mammals, etc. we need insects.  LOTS of insects.  Native plants co-evolved with our native insects and are therefore the best food for them.  Larval host plants are very important in maintaining a healthy population of caterpillars and butterflies.  This is crucial for the butterflies obviously, but it’s also crucial for birds.  95 to 100% of a fledgling’s diet consists of caterpillars.  No caterpillars = no birds.  Dr. Tallamy and his interns have compiled lists of native plant genera and just how many species of butterflies and moths they support.  His lists of ‘Best Bets’ for herbaceous and woody plants are tailored for the mid-Atlantic states because he resides in Delaware, but there is much overlap between the Southeastern and Mid-Atlantic ecosystems.  He did say that the USDA is probably going to hire his intern to compile lists for each of the 50 states, so we’ll be eagerly awaiting the Georgia list.  Oak seems to be the champion of larval life support.  Most of us don’t have the space for an oak, or more likely already have a few in/over our yards, but native plum/cherry trees in the Prunus genus are great understory trees and they support over 400 species of caterpillars! As soon as I get the chance the Crepe Myrtle (from India) in my yard is out and a Chickasaw Plum (Prunus angustifolia) is in!

IMG_20130718_135548_537

      Tradd Cotter (pictured above) gave a very entertaining and informative talk about fungus and their associations with plants.  If insects are the crucial link between plants and larger animals, then fungus are the crucial link between soil nutrients and plant roots.  He also led a nature walk to demonstrate how to ID various types of mushrooms and other fungi.  His company, Mushroom Mountain is a great source for local spawn if you wish to grow edibles in your backyard, but they are also heavily involved in mycoremediation.  It still amazes me that people think that mushrooms in the lawn or garden are a bad thing.  They make soil, join plant roots into nutrient sharing networks to the benefit of all, and break down complex chemical structures into plant food essentially.  Tradd also mentioned in his talk that he had found a fungus strain that preys solely on fire ants, turning them into the infamous “zombie ants” featured in a ‘Planet Earth’ sequence.  I don’t know about you, but if I could wipe out the fire ants in my yard with absolutely no toxic chemicals and the myriad of problems they create I’d gladly pay good money for some of those spores. They are still testing that strain to make sure there are no unforeseen environmental impacts.

      Last but certainly not least, Janisse Ray gave a very impassioned and inspiring talk about seed saving, the need for the decentralization of our food supply and the creation of local plant/seed exchanges.  She has a new book out about seed saving called The Seed Underground. (AJC article about it here) Pandra bought a copy and got her to sign it.  She said it took forever because Janisse was having a conversation with everyone and gave them a hug after signing.  One of her previous books, Ecology of a Cracker Childhood, is a beautifully written account of her childhood in South Georgia and I urge everyone to read it ASAP.  She still lives and works in South Georgia on Red Earth Farm, and will be speaking in Atlanta in November.  Here is a Youtube video of one of her speeches to get you excited about it.

    We both had a great time, made lots of new friends and contacts, and learned quite a bit.  I’m already looking forward to next year!