Marvelous Milkweed Herbivores

All plants are involved in an evolutionary battle with herbivores, where plants evolve various traits that deter herbivores and then herbivores evolve the ability to eat them again. This evolutionary struggle has raged on for over 400 millions years, contributing to the massive diversification of both plants and the wide range of herbivores that eat them. So much so that plants and herbivores make up a majority of the diversity of life on earth, at least among organisms bigger than microbes. In some cases this evolutionary struggle results in plants and herbivores that have all sorts of fascinating traits and behaviors.

Milkweeds (genus Asclepias) evolved an impressive array of defenses against herbivores, including toxic cardenolides that stop insects’ hearts, gooey latex which gums up their mouths, and obnoxious hairs which make munching through leaves a hassle. These defenses work really well because most insects don’t even bother trying to eat milkweeds at all. But, unfortunately for the milkweeds, and fortunately for fans of really awesome insects, there are a bunch of herbivores from all across the insect tree of life that evolved to feed on milkweeds and only milkweeds, and they’ve gotten really good at it. Most of them are brightly colored to warn predators of their toxicity (called aposematic coloration). And they are toxic because, amazingly, they can tolerate the toxic cardenolides in the milkweeds and then incorporate them into their tissues. An exceptionally clever adaptation that turns a plant’s defense into a tool to deter predators.

In a recent walk around Sleepy Hallow State Park outside of Lansing, Michigan, I saw a bunch of these milkweed specialist. First is a one we are all familiar with, the caterpillar of the monarch butterfly:

Monarch (Danaus plexippus)Monarch (Danaus plexippus)Monarch (Danaus plexippus)

The fruits of some of the milkweeds were coated with large milkweed bugs (Oncopeltus fasciatus):

Large milkweed bug (Oncopeltus fasciatus)Large milkweed bug (Oncopeltus fasciatus)

Then I found one of my favorites, the swamp milkweed beetle (Labidomera clivicollis):

swamp milkweed beetle (Labidomera clivicollis)swamp milkweed beetle (Labidomera clivicollis)

There are two aphid species that commonly feed on milkweeds, the bright yellow oleander aphid (Aphis nerii), which is actually and introduced species in North America, and the more drab-colored milkweed aphid (Aphis asclepiadis). Both are commonly tended by ants who collect sugary honeydew they excrete and then, in some cases, protect them from predators.

oleander aphid (Aphis nerii)

milkweed aphid (Aphis asclepiadis)I found one more caterpillar that feeds on milkweed, the delightfully fuzzy milkweed tussock caterpillar (Euchaetes egle):

milkweed tussock caterpillar (Euchaetes egle)milkweed tussock caterpillar (Euchaetes egle)

There is also one more really rad milkweed herbivore I didn’t find, the red milkweed beetle (Tetraopes tetrophthalmus), but check out some these great photos of them by Ellen Woods (1, 2, 3, 4).

As the sun set I was excited that I found so many fascinating and photogenic animals during a short walk near the lake.

20150912-20Thinking about the perennial struggle between plants and herbivores reminds me of the last line in Darwin’s Origin of Species “from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved”, which so succinctly summarizes how fulfilling it is to carefully observe, understand, and appreciate the marvelous diversity of life which surrounds us.

Three Jumping Spider Shots

Here are three looks at a stunning jumping spider I found on a tall reed near the Savannah River in South Carolina. First with a white background showing the huge fuzzy forelegs and red-spotted abdomen, then a close-up portrait with the metallic green chelicerae, then a wide angle macro shot with a horse pasture, trees, and rainbow in the background :)


Life and Death

I found abundant signs of life and death in a recent walk through the woods

jumping spider with midge

Jumping spider eating a midge

Zelus sp.

Assassin bugs stalking

Zelus sp.

fly carpenter ant

Carpenter ants dragging a still living fly back to their colony

green bottle fly

Blow fly waiting for something to die

racoon nest

Squeaks from a hollow tree trunk

baby raccoon with mom

Raccoon cubs squabbling and breastfeedingskunk cabbageAnd skunk cabbage emerging after a long winter

Spanish Moss – Delightful Dangling Denizens of the South

Expansive live oaks dripping with spanish moss–a quintessential scene of the southeastern United States.

Spanish moss (Tillandsia usneoides)

Contrary to the common name they are not actually a moss, rather a flowering plants in the Bromeliad family. They can reproduce from seed or by chunks moved by wind or birds, who use them for nest building. Their arboreal tangles provide important habitat for a wide diversity of arthropods including a highly specialized jumping spider which appears to only live in spanish moss.

Spanish moss (Tillandsia usneoides)

Spanish moss (Tillandsia usneoides) live a pretty strange life style, for a plant. As “air plants” they spend their whole lives draped over tree branches far from anything resembling soil. So despite inhabiting only wet semi-tropical regions they are at serious risk of desiccation. To combat this they have a specialized water efficient form of photosynthesis called CAM Photosynthesis. This is the same trick that cacti use to conserve water. Up in the trees spanish moss must also find nutrients. Instead of having roots their long slender leaves are covered in scaly hairs that can absorb nutrients and water. Nutrients comes through rainwater and dust and also from the trees they inhabit. They are not stealers like parasitic mistletoe, rather, they soak up what washes out of tree bark and leaves. This source of nutrients is important enough that trees which leach few nutrients do not provide suitable habitat for spanish moss.

Spanish moss (Tillandsia usneoides)

Spanish moss is also quite useful to humans. Up until the advent of synthetic fibers spanish moss was harvested from the ground after storms or directly from trees, then heaped into piles to decompose for a few weeks leaving just the dark elastic cords that make up the plants’ center. These were dried and cleaned, then used to stuff mattresses, car seats, or spun into rope, just to name a few uses. Spanish moss is also potentially useful as a simple way to monitor air pollution. Because they absorb particulates from the air which then accumulate in their tissues, measuring levels of toxic substances like Mercury in spanish moss may provide an accurate measure of air pollution in the area.

The South provides many natural history gems, but the ones hanging from the trees are among my favorites.

Photos taken on Sapelo Island, Georgia

Spring Is a Time of Firsts

The first unwavering stare from a reptile

Common garter snake (Thamnophis sirtalis)

The first butterfly

Comma (Polygonia c-album)

The first disappearing act

Comma (Polygonia c-album)

Comma (Polygonia c-album)

The first leaves reaching for the sun

Mayapple (Podophyllum peltatum)

And the first flowers calling out

Spring beauty (Claytonia virginica)


Common garter snake (Thamnophis sirtalis)

Comma (Polygonia c-album)

Mayapple (Podophyllum peltatum)

Spring beauty (Claytonia virginica)

All photos taken 25 April 2015 in the broadleaf forests of Nancy Moore Park in East Lansing, Michigan.