Sunday, September 21, 2014

Bot Flies in Maine

Note: This program first aired on September 20, 2014.

There are so many reasons I am grateful to live in Maine. One of those reasons is the list of things I just don’t need to worry about, like poisonous snakes. The historic and even then very rare reports of timber rattlers in the far western mountains never cross my mind when I am in the woods. Also on that list are poisonous spiders, both poisonous species that are occasionally found here are not native. Brown Recluses and Black Widow spiders make their way into Maine using the time honored tradition of non native species everywhere, they let us transport them, in this case on things like bunches of bananas or grapes, or shipments of used furniture. Our biting insects, though fierce, are typically not deadly. I don’t have to worry about getting malaria or dengue fever from a mosquito bite. Our long winters keep all kinds of tropical maladies and pests from becoming issues here in Maine.

Typically the host survives the bot fly. Not this time.
All of this got turned on its head after a conversation I had last week with Susan Hayward, naturalist extrordinaire and a founding co-director of the Maine Master Naturalist Program. She was commenting on my recent program about horn worms (aka hawk moth larvae) and the curse of the naturalist to be simultaneously fascinated and repulsed by something. She shared her own experience of recently watching a bot fly larva emerge from a meadow vole. Wait, what?? A bot fly larva? We have bot flies in Maine?

Bot flies are a pest that I typically associate with warmer places. The fly lays an egg that ends up contacting your skin, and the egg hatches stimulated by the heat of your body. The tiny larva then burrows below your skin, into your body and sets up shop. It feeds on your flesh and breaths through a hole it maintains at the surface of your skin.  It gets big. Once it is developed enough, it crawls out of your body, drops to the ground and pupates in the soil. Everything about this is simultaneously fascinating and revolting, but it was never something I thought I had to worry about here in Maine.

And it turns out, actually, I was right. We do indeed have bot flies in Maine, but there are lots of different kinds of bot flies, and as parasites, they tend to have good fidelity to their host species. The bot fly Susan saw was in the genus Cuterebra which tend to attack rodents. The flies lay eggs in the entrances to rodent burrows, and as the animal moves past, the eggs hatch and the larvae, well, you know what they do. Apparently, from the number of veterinary web sites out there, its not unheard of for pets to get a bot fly, perhaps from sniffing around rodent burrows. Horse and other live stock owners know about bot flies (other species) too. Apparently I was the only one who didn’t know. And if I had thought about it, all the books I’ve read about the arctic talk about caribou infested with warble flies, which is another name for bot fly, so they venture even further north than here.

It is apparently quite rare but not unheard of for humans to get parasitized by bot fly larvae in this part of the world, but if you need something to worry about, feel free. I am going to put the rodent parasitizing bot flies in the same box in my brain as timber rattlers and brown recluse spiders, the one labeled “cool, possible, but not worth worrying about”. I encourage you to do the same. And one more thing, if you want to know more about bot flies, my advice is, don’t google this while you are eating.

Photos courtesy of Susan Hayward.


Images of Rodent and Rabbit adult bot flies

Tuesday, September 9, 2014


Note: This program first aired on September 6, 2014.

I am a vegetable gardener and this year I went out of my way to pick a tomato variety that would yield large and plentiful fruits. I am lucky enough to have a green house, and though I don’t give my tomatoes all the attention they deserve, they thrive in the heat and grow to heights well above my head. My peppers do just as well, and year after year I am amazed that such large and productive plants can grow from such tiny seeds.

The end of summer is always a whirlwind of activity, and this year was no different. I walked into the green house last week after several days away and noticed some of my pepper plants seemed to be missing a lot of leaves. Then I noticed many dark green blobs and blotches on the soil under the plants, and it slowly dawned on me that something was eating my pepper plants, and I knew just what it was. With a search image in my head, I quickly found the unbelievably large caterpillars that were munching away, confirming my fears. The hornworms are back.

The hornworms in this case are Tobacco Hornworms, Manduca sexta . They and their closely related cousins Tomato Hornworms, are common garden pests, generally showing up on tomato plants in late summer, capable of defoliating a plant seemingly overnight. If you aren’t paying attention at just the right time, you can lose all of your tomato plants. We tend to find them on tomatoes, but they feed preferentially on most members of the Solanaceae including tomatoes, peppers, potatoes and tobacco.

If you have never seen one, they are amazing looking, and sort of freaky. They grow to a size larger in length and diameter than my finger, and according to one source, can actually bite when attacked. Some how I never seem to see one when they are small, but they do start out that way. They are the larvae of Sphinx moths, large nocturnal moths that lay eggs on the host plant in summer. After a few days the eggs hatch and the larvae emerge, feeding for three weeks, and apparently growing from a tiny hatchling, to a caterpillar larger than my finger. They then pupate in the soil, burrowing under the surface and remaining there for at least three weeks. In the first generation of the summer the adults emerge in three weeks. Those adults then mate and lay eggs, and that second generation pupates and overwinters in the soil, with the adults emerging in late spring or summer of the next year. And just like the larvae when they are small, I never seem to see the adult moths either.

The crux of the matter is this, my feelings about the hornworms are complicated. On one level, they are amazing. Huge puffy green caterpillars with beautiful markings and bizarre appendages, they are hard to draw your eyes away from. On another level they are pests, they destroy my tomatoes and are so well camouflaged you are never sure you found them all. When I do find one, I invoke the circle of life and feed it to my chickens. On a final, and more visceral level, I find them disgusting. Though I know better, when I see them I feel a distinct physical sensation in the pit of my stomach, it’s revulsion. Something in my animal brain reacts badly to these enormous grub like larvae, even when my human brain says “wow! Cool!” quickly followed by “darn those pests!”.  I take it to mean that there is something in my evolutionary history that is speaking up, something that is telling me not to eat these hornworms, and I don’t have any way to assure my animal brain not to worry, there is no chance of that. So I am left simply with this strange tension between the very old and the very new. If we pay close attention, I think we will find this tension in many parts of our lives. Whether or not we can rectify it, it is worth being aware of. It’s a window that allows us to look at where we came from, how we lived, and how far we have come from that today.

Tuesday, September 2, 2014

Lobster Mushrooms

Note: This show first aired on August 30, 2014.

Last week I was in western Maine, enjoying a last blast of summer vacation. Hiking through the mixed woods around Flagstaff Lake, I was amazed by the abundance of fungus growing in the woods. We saw several different coral fungi, puffballs, earth tongues, amanitas, slime molds and many different kinds of mushrooms. Late summer and fall are peak times for fungal fruiting activity, as long as there is sufficient moisture and we were clearly there at the right time. Fungi are very ephemeral, responding to temperature and humidity, and the species you see around you fruiting on the forest floor change from week to week and even day to day.

The species that made the biggest impact on me however, was the lobster mushroom, otherwise known as Hypomyces lactiflorum. They were everywhere, huge and bright orange and erupting out of the duff and leaf litter. They are called lobster mushrooms due to their orange color, looking something like the orange of lobster meat, or cooked lobster shells, and they are reportedly edible, though I doubt they bear any culinary resemblance to lobster.

The lobster mushroom’s claim to fame or dirty secret is that it isn’t really a mushroom at all, not in the conventional sense anyway. What we see and call a lobster mushroom is actually a mushroom of one of two common genera that has been parasitized by the Hypomyces lactiflorum fungus. Hypomyces has no shape of its own, its mycelium (or generic fungal fibers found in soil everywhere in the forest) live in the soil among the mycelium of its host species. When the host species fruits, the term for creating a mushroom, Hypomyces invades and uses the host’s mushroom for its own purposes.  And what is the purpose of a mushroom? It is the reproductive structure of many kinds of fungi. When the mycelium of two separate fungal individuals of the species meet in the soil, they exchange genetic material and the resulting mushroom is simply the above ground tissue where the spores  (which are analogous in many respects to plant seeds) are formed and then released into the air, which is the medium in which they are dispersed. For some reason Hypomyces can’t make a mushroom on its own, so it uses someone else’s. If you look closely at a lobster mushroom, you will see the tiny little sacks that are the fruiting structures of Hypomyces, they cover the surface of the lobster mushroom, and that surface area is what Hypomyces is after. The host fungus also undoubtedly provides nutrition to the parasite, so this is a case of a fungus eating another fungus as well as the story of a reproductive service unwillingly provided by one fungus to another.

The victims of this attack are fungi in the Lactarius and Russula genera. They are both very common in the forest and include hundreds of species. Both form mycorrhizal or mutually beneficial relationships with most trees species as well. In the northeast, Hypomyces typically parasitizes Russula brevipes and Lactarius piperatus.

We are coming into peak mushroom season. I encourage you to get out on a fungal foray of your own. Go for a walk in the woods and take your time, bring a field guide and a camera and spend the afternoon exploring the diversity that can pop up overnight, and disappear just as quickly. And it must be said, you have to be careful. Just because lobster mushroom is named after a food, that doesn’t necessarily mean it is edible. Remember it’s a parasite, and you can’t identify the host once its been parasitized. There are people out there who can teach you about wildcrafting edible mushrooms, I am not one of them. So please, due diligence is in order. Fungal appreciation is a life long pursuit, I am enjoying the state of “beginners mind” I find myself in, where the discovery and identification of a common species brings excitement and joy. I hope this fall, you will join me in this simple pleasure.


George Barron’s Mushrooms of the Northeast North America, Lone Pine Press 1999, one of my favorites, nice photos.

David Arora Mushrooms Demystified Ten Speed Press 1979, 1986 The definitive mushroom book for most of us! Pacific Northwest centric, but still useful. Dense, and lacking lots of pretty pictures (most are black and white). Clearly kooky author.

Lawrence Millman Fascinating Fungi of New England Kollath and Stensaas Publishing 2011

Tom Volk’s webpage on Hypomyces:

Kids and Summer

This program first aired on August 23, 2014.

This week's show was one of the super fun kids shows I do from time to time. I won't bother to post a transcript, but I would recommend that you give it a listen here.

In the spirit of kids and the outdoors, I also encourage you to check out Richard Louve's organization the Children and Nature Network. While we in Maine don't usually have a hard time getting outside, technology is encroaching further and further into our wild lives, and Louve and his organization are working hard to do something about it.