That's One Big Caterpillar

While on Harsen's Island in St. Clair County, Michigan last week, Tony Troche found a thick, enoromous caterpillar. After a quick check on someone's fancyphone, we were able to determine that our caterpillar was that of a Cecropia Moth (Hyalophora cecropia).


A couple of years ago, Lindsay found a dead Cecropia Moth in our driveway. To see that post, which includes more information on the species, click here.

A Fen-tastic Saturday Morning, Part III

In my previous two posts, I discussed the plant communities and some of the plants present in three of northeastern Indiana's highest quality fens. While botanizing these preserves, Nate Simons and I noticed a few common butterflies and moths that certainly deserve a place on this blog.


In the photograph above, a Monarch (Danaus plexippus) is feeding on nectar from Spotted Joe-Pye Weed (Eupatoriadelphus maculatus). Monarchs are protected by chemicals they obtain as caterpillars that are toxic and taste bad to potential predators. These heart toxins come from milkweeds (Asclepias spp.), and are often many times stronger in the Monarch caterpillar than they are in a milkweed plant.

While most people are familiar with the phenomenon of bird migration, relatively few are aware that millions of Monarchs depart on similar journeys each fall and spring. Many of our butterfly species overwinter as adults, caterpillars, or pupae; however, our winters are just too cold for Monarchs, so they annually travel south (some up to 3000 miles!) at the end of our warm season. Monarchs who have summer homes in eastern North America all travel to the Sierra Madre Mountains in Mexico, whereas those in western North America make their way to California. To stay warm during their migration and during the winter, congregations of up to tens of thousands of Monarchs cluster together on a single tree. I hope to someday visit the Sierra Madre Mountains in February to see this amazing sight. As seen on the Journey North webpage, this year's Monarch migration is already underway!

The most amazing part about this migration phenomenon is that the butterflies that migrate this year are several generations removed from those that migrated last year. Once Monarchs return back to North America in the spring, they lay eggs in March and April and then die soon after. Those eggs eventually develop into caterpillars, then into adults that lay eggs and then die. The next generation hatches in May or June, and the next generation after that is born in July or August. Finally, after all of these adults have lived their short lives, another generation is born in September or October. It is this generation that migrates, hibernates, mates, then migrates back to North America to lay eggs and die. One of the great mysteries of our natural world is how the migrating generation of Monarchs knows where to go each fall, as it was their great-great-grandparents, who died several months earlier, that last made the long journey to Mexico or California.


After reviewing the fritillaries in several of my resources, I came to the conclusion that the butterfly above is an Aphrodite Fritillary (Speyeria aphrodite). On another of my photos, the silver spots on the hindwing undersides of this butterfly are conspicuous. Aphrodite Fritillaries have only a single brood each year, with adults typically present from June to September. Eggs are laid in the late summer and caterpillars hatch in the late summer or early fall. The caterpillars then overwinter and begin feeding on violets (Viola spp.) the following spring.


Question marks and commas aren't just forms of punctuation, you know. In fact, they are both species of butterflies. The butterflies going by these names are also quite similar in appearance. When looking at the upper surface, the two species can be distinguished by looking for an extra dark spot on the forewing present in Question Marks (Polygonia interrogationis) but not in Eastern Commas (Polygonia comma). This extra spot is the horizontal rectangle near the top and outside edge of the forewing on the Question Mark shown above.


Another way to tell a Question Mark from an Eastern Comma is to look at the underside of the hindwing, where each species bears the tiny silvery punctuation symbol for which it is named. As seen above, this butterfly is therefore a Question Mark; an Eastern Comma would lack the dot underneath the comma on the underside of the hindwing. Another way to tell the two similar species apart is that Question Marks have longer hindwing tails than do Eastern Commas.

In addition to feeding on nectar from flowers, Question Marks also feed on tree sap, decaying fruit, animal droppings, and carrion. They often overwinter as adults.


The first three species highlighted in this post are butterflies, but the caterpillar above is that of a moth. Specifically, this grayish-green larva is the caterpillar of the Hitched Arches Moth (Melanchra adjuncta), feeding on leaves of Ohio Goldenrod (Solidago ohioensis, or Oligoneuron ohioense). Thanks to Ben Hess of Ben and Joy, who let me know that Janet Creamer of Indy Parks Nature Blog and Midwest Native Plants, Gardens, and Wildlife had identified this caterpillar for him just a few weeks ago. And thanks, Janet!

That wraps up my account of my visit to some of the fens of northeastern Indiana this September. As you can see, these unique communities are home to a nice variety of unique plants and animals, but my reports barely scratch the surface.

Garden "Pests"

I had hoped to be able to post about the St. Joseph County Parks - Spicer Lake BioBlitz that took place this past Saturday, but because the rain never let up from the time we began until about 6 PM, I never even took my camera out of its case.

Instead, here are a couple of "pests" that I found in our garden when picking vegetables this past Friday. Personally, I enjoy having these "pests" around, and considering how tired Lindsay is of trying to come up with new ways to prepare and preserve tomatoes and peppers, she is probably pretty happy to have them as well.


This is the caterpillar of a Black Swallowtail (Papilio polyxenes) butterfly, feeding on the leaves of our carrot (Daucus carota) plants. Black Swallowtails not only thrive in areas of agriculture, but they are even said to be declining in the northeastern United States, where former agricultural areas are being converted to forests. In addition to carrots, Black Swallowtail larvae can be found feeding on other members of the carrot family (Apiaceae), as well as members of the citrus family (Rutaceae).


I have only ever seen these caterpillars with this coloration of lime green with black bands, each with six yellow spots, but apparently the green coloration can be replaced by white on some specimens.


Another "pest" that I found was munching on our jalapeno pepper (Capsicum sp.) plants. This is the larval stage of the Carolina Sphinx (Manduca sexta) moth, also known as a Tobacco Hornworm. This is one enormous caterpillar, reaching a length of 9 cm! As the common name implies, Tobacco Hornworms are often found devastating tobacco (Nicotiana tabacum) crops, but just as commonly they are found on tomatoes (Solanum lycopersicon), peppers (Capsicum spp.), and other members of the nighshade family (Solanaceae). Because of their attraction to tomato plants, they are often referred to as Tomato Hornworms, but this common name is said to refer to a different species, the caterpillar of the Five-spotted Hawk Moth (Manduca quinquemaculata).

Before I found this caterpillar, which in spite of its size blends in very well, I noticed that the fence around our garden had been broken in one spot, coincidentally near our pepper plants. Considering that Tobacco Hornworms are voracious eaters, I can't help but wonder now if it didn't eat through our fence to get to the peppers!

Pine Station and Clark and Pine Nature Preserves

For each of the past several years, Shirley Heinze Land Trust has asked me to lead one of their member hikes at northern Indiana preserves. This year, my hike was at Pine Station and Clark and Pine Nature Preserves in Lake County. The hike that I led took place a couple of weeks ago, and I wanted to post some of the highlights.


The two dedicated state nature preserves are on opposite sides of Clark Road, with Clark and Pine on the west and Pine Station on the east. The highlight plant at these preserves is the State Endangered American Blue Hearts (Buchnera americana, shown above), a plant of moist sandy prairies with a scattered distribution throughout the eastern United States. American Blue Hearts is considered "one of our very rarest plants" according to Plants of the Chicago Region (1994), and it is considered the plant responsible for initially bringing legendary botanist Floyd Swink to Chicago (be sure to see this link for an account on Floyd, including the story about him, the great Julian Steyermark, and American Blue Hearts).


Clark and Pine Nature preserve consists of shallow swell-and-swale topography, with aquatic plants such as Water Shield (Brasenia schreberi), White Water Lily (Nymphaea odorata), and Variegated Yellow Pond Lily (Nuphar variegata) dominating the swales and mesic prairie plants dominating the swells. When standing at this site, it is always amazing to think of all of the development and destruction that has taken place immediately surrounding these preserves, yet that this kind of quality still exists on much reduced postage stamp parcels. In fact, Clark and Pine Nature Preserve is said to harbor more species of concern (plants and animals combined) than any other nature preserve in Indiana. Another of these state listed species, Purple Bladderwort (Utricularia purpurea, State Rare, shown below) is so common at this site as to form a purple haze over the swales in July and August.


One of our first field trip observations as people were arriving to hike the preserves was an enormous Polyphemus Moth (Antheraea polyphemus) caterpillar feeding on Sandbar Willow (Salix interior) along the road. This caterpillar, immortalized below, was nearly as large as my index finger, both in length and girth. And let me tell you... I have one hefty index finger!


As we were observing and photographing this caterpillar, we found another green caterpillar, that of and IO Moth (Automeris io) feeding on the same colony of Sandbar Willow. As I was telling those in attendance not to touch this caterpillar, shown below, because those bristly barbs may sting, someone assured me that yes, they do sting, as they had just rubbed up against it and felt its wrath.


Sand mining took place historically at Pine Station, leaving swaths of panne community in areas that were historically mesic prairie swells. Near the Great Lakes, when sand is excavated down to the water table, a unique and rare flora often results, yielding an expression of a seed bank that must be thousands of years old (see my commentary on this topic posted at Get Your Botany On!). The dominant plant species in the man-made panne shown below include Twig Rush (Cladium mariscoides), Golden-seeded Spike Rush (Eleocharis elliptica), Baltic Rush (Juncus balticus var. littoralis, State Rare), Hair Beak Rush (Rhynchospora capillacea), and Low Nutrush (Scleria verticillata). Plant species of conservation concern are common to abundant in this scrape.


One of the plants that often shows up in these scrapes but that occurs naturally in calcareous sands and fens is Kalm's Lobelia (Lobelia kalmii, below). This delicate plant is much more attractive to me than its more conspicous and gaudy relatives Cardinal Flower (L. cardinalis) and Great Blue Lobelia (L. siphilitica), which are much more generalist species in terms of where they will grow.


Another species of concern, Common Bog Arrow Grass (Triglochin maritimum, State Rare, below), is more abundant in this panne than I have seen it anywhere in the state. According to Derek Nimetz of Indiana Department of Natural Resources - Division of Nature Preserves, this species has done extremely well where recreational 4-wheelers have driven through the site. Species like this require periodic disturbance, as they need their space and don't do well in the presence of much competition. Thanks, illegal 4-wheelers!


While walking through the panne, I scared up a Great Egret (Ardea alba, State Special Concern, below), whose white feathered body made for a statuesque subject against a cloudless sapphire sky.


As expected, Pine Station and Clark and Pine Nature Preserves proved an excellent location for a late July field trip.

Goose Pond Fauna, And A Final Note On The Goose Pond Biodiversity Survey

I've already posted in general about the recent Goose Pond Biodiversity Survey, and in more detail about the results of our vascular plant survey, so this post will be dedicated to the fauna observed during the event.

The bird highlight for me was seeing so many Black-necked Stilts (Himantopus mexicanus) throughout the marsh communities. Aptly named for the black plumage on the backs of their necks and the long, pink legs, this shorebird species was not known to breed in Indiana until as recently as 2005. With the restoration of ~4,000 acres of marsh habitat, Goose Pond is now a hot spot for this otherwise primarily coastal species, as 19 Black-necked Stilts were tallied during the two-day survey.


In the seeded prairies, Sedge Wrens (Cistothorus platensis) were singing constantly. Unfortunately, I wasn't able to get photos of the Henslow's Sparrows (Ammodramus henslowii) that were also giving their insect-like "tsilik" songs from the same prairies. Both of these grassland species are listed as State Endangered in Indiana, and without the installation of ~1400 acres of prairie on the preserve, they would not be as successful in Greene County, Indiana as they are today.


A common butterfly, Gray Hairstreak (Strymon melinus), has also benefitted somewhat from the restoration at Goose Pond; however, this species is widespread and often thrives in weedy old-field areas as well as prairies. If you're not watching for butterflies, this one can go undetected, as its wingspan only totals ~1 inch.


The much more conspicuous species shown below is a female Black Swallowtail (Papilio polyxenes), which has a wingspan of 3 1/4 to 4 1/4 inches. Black Swallowtails are found throughout the eastern 2/3 of the continental United States, in all sorts of open habitats.


Thanks to Don Gorney and Sandy Belth for verifying my butterfly identifications.

The Smartweed Caterpillar (Acronicta oblinita) is a common species of open, often moist habitats throughout eastern North America. As the common name implies, larvae of this species often feed on smartweeds (Polygonum spp.), but they will also feed on a variety of other plant species including forbs, shrubs, and trees. As an adult moth, this species is known as a Smeared Dagger Moth. Identification in the field was made by Ben Hess.


One of the common dragonflies observed at Goose Pond was the Common Whitetail (Plathemis lydia, aka Libellula lydia), a member of the group known as Skimmers. Common Whitetails display sexual dimorphism, as the males (shown below) and females look quite different. This conspicuous species can be found in nearly any wet area throughout the Lower 48, as well as in southeastern Canada.


Another common dragonfly found in abundance at Goose Pond was the Blue Dasher (Pachydiplax longipennis). Another "Skimmer," this species is also widespread, found in all types of wet areas throughout most of the contiguous United States and into portions of southern Canada. In the photograph below, the male Blue Dasher is shown in "obelisk" position, a posture taken to reduce the amount of surface area exposed to the sun to prevent overheating. As you can see in this Wikipedia link, the posture of the Blue Dasher below is in fact reminiscent of an obelisk.


For most of the two days, my eyes were focused on the ground, so my fauna observations were limited. However, the article below, printed in the Bloomington Herald Times, gives a nice recap of the wildlife that was observed, and of the biodiversity survey in general.

Portrait of life: Goose Pond biodiversity survey paints a picture of wildlife that call southern Indiana wetlands home
By Dawn Hewitt
7/25/2010
Who would have dreamed that bog lemmings live at Goose Pond? The small rodent is found in grassy openings in forests and forest edges, especially where sedges, ferns and shrubs grow, and not in corn and soybean fields. Somehow, the hardy little mammals survived a century of draining, plowing, row crops, pesticides, fertilizers and bulldozing during wetlands restoration.

The critter was one of thousands caught and cataloged July 16 and 17 during the first Goose Pond Biodiversity Survey. The newly restored, 8,000-plus acre state fish and wildlife area is teeming with life. The bird species the wetlands have attracted have been well documented and jaw-dropping at times. But what else is out there?

Scientists from across the state and beyond joined forces to address that question. Organized and co-sponsored by the Indiana Academy of Science and Friends of Goose Pond, 82 biologists, including botanists, ichthyologists, lepidopterists and other entomologists, herpetologists, mammalogists, ornithologists and biogeochemists went into the fields and marshes in an attempt to paint a two-day, summertime picture of all life forms present there.

While the lemming was a shocking find, many scientists were more impressed with the sheer numbers of organisms found.

“We didn’t find anything exceptional, but the abundance is phenomenal,” said herpetologist team leader Daryl Kerns, with the IAS and a biology professor at Hanover College. The school’s Rivers Institute was also a key player in organizing the event.

Goose Pond property manager Brad Feaster provided some preliminary results:
• Vascular plants: more than 400 species identified so far
• Beetles: 79 species and counting
• Butterflies: 47 species
• Moths: 41 species and counting
• Dragonflies: 22 species
• Reptiles and amphibians: 19 species
• Birds: 123 species

Many reports and final tallies are still to come from the 13 teams that were in the field that weekend. Team leaders have until Aug. 16 to submit their results, and some will spend a month sorting, identifying and counting.

The entomologists collected literally buckets of bugs that will take weeks to identify. Some set up bright lights in fields at night, and the insects dove by the thousands onto collecting sheets.

The final results will be published in the Proceedings of the Indiana Academy of Sciences and will also be made available to the public. Such a list already exists for birds on the web at www.in.gov/dnr/fishwild/3094.htm.

Other species likely or known to be at Goose Pond will not show up in the survey because they are dormant this time of year, or simply weren’t found on the two-day search, Feaster said.

“This one event will significantly expand our knowledge of the biota at Goose Pond Fish and Wildlife Area,” Feaster said.

Barbara Simpson, a member of Friends of Goose Pond and key organizer of the event, said publishing the results will encourage nature lovers to document additional species there. “It will be like an on-going treasure hunt,” she said.

Simpson said the success of the survey includes more than species tallies, but also the enthusiastic participation of scientists, students, nature lovers and volunteers, all of whom donated their time and expertise to the project, including travel expenses. In return, they got free meals and lodging, a chance to socialize with like-minded biologists, and an opportunity to explore the re-established wetlands.

Goose Pond is “well-managed for diversity, and suitable to become a world-class natural resource,” Kerns said.

Which End is Which?

Take a look at the caterpillar in the photograph below and see which end you think is the head, and which end you think is the rear.


Many caterpillars have developed defense mechanisms to ward off predators. Some of those mechanisms include camouflage, mimicking other animals in appearance (e.g. snakes), chemical defense, mimicking poisonous caterpillars in appearance, intense and sudden movement, pretending to bite, regurgitating, and hissing; yet another defense mechanism is possessing a "false head" (Wagner 2005). In some caterpillars, like the Spicebush Swallowtail, the false head is located over the thorax. More commonly, the false head is located at the opposite end of the body.

In the Turbulent Phosphila (Phosphila turbulenta) shown in these photographs, the head appears to be at the end facing my camera in the photograph above. However, the shiny, black, true head of this caterpillar is at the end facing my camera in the photograph below, hidden under the black and white prothoracic shield (the shield over the first segment of the thorax).

Predators often attack the head end of a caterpillar (Purser 2003), so possessing a false head is a way to potentially survive an attack. When the false head is attacked, caterpillars that possess them regurgitate, bite, or emit a poisonous substance (Wagner 2005).

Lindsay and I found this caterpillar at Starved Rock State Park near Utica, Illinois a few weeks ago. It was on a handrail along a trail, with a leaf that had fallen off of a Roundleaf Greenbrier (Smilax rotundifolia) plant. As it turns out, the Turbulent Phosphila feeds on... you guessed it, greenbrier; they often feed in groups, and have been known to defoliate plants (Wagner 2005). You can find this boldly patterned caterpillar in open woods throughout much of the eastern United States (Wagner 2005).

Purser, Bruce. Jungle Bugs: Masters of Camouflage and Mimicry. Buffalo, New York: Firefly Books, 2003.

Wagner, David L. Caterpillars of Eastern North America: A Guide to Identification and Natural History. Princeton and Oxford: Princeton University Press, 2005.

A Late Season Caterpillar

Last week at a site in Lake County, Indiana, Tony Troche and I observed a very interesting caterpillar climbing on a stem of Flat-topped Aster (Aster umbellatus). I actually thought that the caterpillar was moving up the stem, but in fact, it is moving down. The humped eighth abdominal segment is one of the identifying characters for this colorful caterpillar.


This is the larval stage of a Brown-hooded Owlet (Cucullia convexipennis), also known as the Brown-bordered Owlet and the Brown-bordered Cucullia. An excellent description of this caterpillar can be found in Caterpillars of Eastern North America: "Each individual appears as if it were hand-painted and then glazed." Brown-hooded Owlets are found from Nova Scotia south to Georgia, and west to Minnesota and Missouri. Host plants for this species include asters (Aster spp.) and goldenrods (Solidago spp.).

A photo and description of the Brown-hooded Owlet moth can be found at nearctica.com.

Our New Pet

Don't worry... Bootypants is still doing just fine...

But now, we've got another furry friend at our house. For at least the past week, this Giant Leopard Moth (Hypercompe scribonia, = Ecpantheria scribonia) caterpillar has been in and around our garage. Giant Leopard Moths are also known as Great Leopard Moths and Eyed Tiger Moths. This species is found in forests throughout the eastern half of the United States and into southern Canada. Giant Leopard Moth larvae overwinter as caterpillars, often hidden under loose bark on a tree, under a log, or in leaf litter. They are polyphagous, meaning that they will eat a variety of food; they are known to feed on oak, willow, banana, orange, cherry, cabbage, dandelion, sunflower, plantain, and violet. They typically stay hidden during the day and feed at night.

At first glance, this caterpillar looks like a large woolly bear caterpillar lacking the brown central section. Its body is mostly black, covered by stiff, black bristles. However, when threatened, the Giant Leopard Moth caterpillar rolls into a ball, exposing red intersegmental rings and spiracles (small openings on the body of the caterpillar that allow air to enter the trachea). This red color warns potential predators that this caterpillar may be poisonous. While its bristles are prickly, this species supposedly does not sting.

While the caterpillar is interesting, take a look at the moth it will become...

This Giant Leopard Moth photograph is from Wikipedia. What a gorgeous moth! With a wingspan of up to 9cm, this is a large moth. We haven't seen this moth on our property, but will definitely watch for them next year.

A Sunday Walk in the Park

Our friends Mike and Ben came to visit this weekend, and we spent Sunday morning at Potato Creek State Park.


Along the trails, Lindsay found a small white and black-striped caterpillar with long, white hairs. The caterpillar was crawling on Canadian Clearweed (Pilea pumila). As you can see, Ben was excited to see this little creature.


I believe that this is a Hickory Tussock Moth caterpillar (Lophocampa caryae), but I don't see the long tufts of black hairs that are commonly found on this species. Hickory Tussock Moths feed on a variety of tree species, including hickory and pecan (Carya spp.), walnut (Juglans spp.), American Hornbeam (Carpinus caroliniana), ash (Fraxinus spp.), elm (Ulmus spp.), oak (Quercus spp.), and willow (Salix spp.). A rash can sometimes form on people who touch this caterpillar, and it has also been said to inflict a sting.

A bit later, Lindsay saw an Eastern Box Turtle (Terrapene carolina) with a beautifully patterned shell scurrying across the trail. The Eastern Box Turtle is one of only two turtle species in Indiana that spends most of its life outside of the water; the other is the Ornate Box Turtle (Terrapene ornata). Amazingly, there are records indicating that Eastern Box Turtles can live up to 120 years old! While this species is not uncommon, studies show that their numbers are decreasing as a result of habitat destruction and collecting.

Near the end of our walk, I spotted a large orange and black butterfly, and was able to get a few photos before it flew off. I think this is a Great Spangled Fritillary (Speyeria cybele), a common species of woodlands and meadows. Great Spangled Fritillary caterpillars overwinter, feed on violets (Viola spp.), and develop into an adult butterfly the following summer. They have been found alive until late September, making them a long-lived butterfly species.

Captivating Caterpillars

For some reason today, even with the thick carpet of white on the ground, I began thinking about caterpillars. I went through my caterpillar photos this evening, taken at various times over the past 5 years, and I have a few to share.

The caterpillar in the photo above is that of a White-marked Tussock Moth (Orgyia leucostigma). White-marked Tussock Moth caterpillars can be found on almost any woody species in eastern North America, but they are most commonly found eating apple, birch, black locust, cherry, elm, hackberry, hickory, oak, rose, willow, fir, hemlock, larch, spruce, and other conifer. The hairs of the caterpillar can cause an allergic reaction, so be careful if you see this one.

This is an American Dagger Moth (Acronicta americana) caterpillar that I found on the side of our house. This caterpillar can range in color from yellowish to white. They are most commonly found in forests and woodlands in eastern North America, and can be found feeding on alder, American hornbeam, ash, basswood, birch, box elder, chestnut, elm, hazel, hickory, horse chestnut, maple, oak, poplar, redbud, sycamore, walnut, willow, and other woody plants.

The IO Moth (Automeris io) caterpillar is a member of a group of caterpillars that have many-branched, poison-filled spines that give a sting that apparently feels like that of stinging nettle (but lasts longer). The IO is found in fields, woodlands, forests, and streambanks in eastern North America from southern Canada to Florida. They can be found feeding on aspen, birch, blackberry, cherry, clover, elm, hackberry, hibiscus, oak, poplar, sassafras, willow, wisteria, and grasses (even corn!).

The Saddleback (Acharia stimulea) is another caterpillar that has stinging spines. In fact, the sting is said to be one of the most potent of North American caterpillars. Even the cocoon of this species can deliver a sting. Saddlebacks can be found in fields, gardens, edges of wetlands, and woodlands through the Midwest and south to Florida and Texas. They can be found feeding on a wide variety of plant species, including apple, aster, blueberry, buttonbush, cabbage, citrus, corn, grass, maple, oak, and garden and ornamental species.

This non-stinging caterpillar is that of a Polyphemous Moth (Antheraea polyphemus). They can be found in barrens, woodlands, and forests throughout North America (except in Arizona and Nevada). Polyphemous Moth caterpillars eat a variety of plants, including apple, ash, birch, dogwood, elm, hazel, hickory, maple, oak, rose, and willow. I've never heard this, but Polyphemous Moth caterpillars have been known to make a snapping sound with their jaws.

The two photos above are both of the same species, Black Swallowtail (Papilio polyxenes). They are found in open fields, farmfields, gardens, wet meadows, and other open wetlands in eastern North America from Canada south to Florida and Texas, and even into Costa Rica. Black Swallowtail larvae most commonly feed on plants in the carrot family (Apiaceae), but can also be seen feeding on rue and on species in the citrus family (Rutaceae). When provoked, black swallowtail caterpillars invert a v-shaped organ (called an osmeterium) from behind the head that looks like a pair of horns. The osmeterium emits a strong odor that is distasteful to predators.

And finally, my favorite caterpillar, the Spicebush Swallowtail (Papilio troilus). Spicebush Swallowtails are found throughout much of the eastern United States, most commonly in woodlands and swamps, but they can also be found in fields and gardens. They feed on sassafras and spicebush. This caterpillar is showing a form of mimicry. Its head looks like that of a snake, especially to a passing bird, who may then think twice before trying to make a lunch of this species.

You'll notice that there are a variety of plants, many trees and shrubs, on which these (and other) caterpillars prefer to feed. Oaks and black cherry are two of the most common food plants to native butterfly and moth larvae. By planting native trees and shrubs in your yard, you can easily attract a variety of caterpillars to your yard. The caterpillars in turn attract birds; you can easily create a functioning ecosystem in your yard just by planting the native species that attract the bottom of the food chain.

Most of the information from this post was taken from Caterpillars of Eastern North America. This is a great book with excellent photographs and valuable descriptions and habitat information. If you're ever looking for a book on caterpillars, I strongly recommend this one.