The Beautiful but Poisonous Milkweed

Its flowers smell like perfume, its colorful blossoms and abundant nectar draw a variety of insects to it.

But only a very few species can tolerate eating the milkweed, because a cut leaf or stem produces a sticky, milky, alkaline sap that is full of toxic chemicals. Monarch butterflies and their larvae seem to tolerate these nasty substances (called cardiac glycosides), and actually sequester them in their body, so that if a naïve predator like a young blue jay tries to eat them, the bird’s digestive system immediately rejects the caterpillar and the bird spits it out. This might not save that particular caterpillar or butterfly, but the bird won’t try eating another one of that kind and remembers “orange and black – don’t eat that”.

This week the first caterpillars showed up, one I had expected, and one I had never seen before.

This Monarch caterpillar is probably just a few days old. In a week or two, it will look more like this one below.



And then I walked over to another clump of milkweed across the yard and found this clump of larvae that had eaten the milkweed leaves literally to the "bone". They had almost completely defoliated the plant.

A little closer view of these half-inch long fuzzy larvae. Turns out these are the Tufted Milkweed Moth (Euchaetes egle). The female lays her monster clutch of eggs on plants without Monarch larvae, which is a good thing since this enormous group are voracious eaters. I captured this bunch and put them in a rearing cage with a couple of 2-foot long milkweed stems, and they managed to demolish all of those leaves in less than two days.

The milkweeds are forming small pods of seeds now, and soon another group will arrive to monopolize these plants – the milkweed bugs.



Milkweed bugs are seed predators and, like the Monarchs, they arrive by migration from points south, in time to harvest the seed crop. It’s always amazing to me that these insects can hone in on scattered patches of milkweed as they move through an urban area like this one. The picture above was taken last August when the pods had matured. Adults and nymphs feed communally on the seeds; they stick their mouthparts through the pod wall, secrete salivary enzymes to digest the seeds, and then slurp back the digested nutrients. We've only seen milkweed bugs on plants in Minnesota the last few years; perhaps its the change in climate that makes it possible for them to come this far north.

Backyard Pollinators

The wildflower garden is almost at maximum flowering, and we’re seeing increasing numbers of butterflies, wasps, bees, flies, and beetles swarming the colorful bouquets.



We haven’t seen honeybees in the garden for several years, but pollination efforts have been amply taken care of by a variety of hymenoptera from tiny sweat bees to larger bumblebees and several types of wasps as well.

The swamp milkweed is in full flower, and emits a sweet fragrance that pulls in quite a few different pollinators, as well as a specialized group of munching herbivores that are
well adapted to handle the toxic cardiac poisons (glycosides) it sequesters in its leaves and stems (but perhaps not its flower nectar).   Yesterday, the plants were full of
bald-faced hornets, a long legged black and white wasp (not a hornet taxonomically speaking), known for its painful, repetitive stinging ability.  They are social and nest in a large papery hive constructed by all the workers, but they seemed to aggressively exclude each other from the particular flowers on which one is foraging.





My camera equipment is inadequate to get good closeups of this less than 1-inch long insect, but this photo shows the striking black and white coloration well);  from (http://bugguide.net/node/view/279221/bgimage).  For more information and some really great close-up photos, go here:  http://www.cirrusimage.com/Bald-faced_hornet.htm .

The hornets moved pretty quickly around each flower cluster, thrusting their heads deep into each flower as they moved along.  It was somewhat comical to watch them try to leave that flower cluster, because the milkweed flower has a unique pollination mechanism that traps the insect’s leg in a tiny cleft where they get stuck until they are able to remove the saddlebag of pollen in that cleft.  The hornets pulled, twisted, buzzed, and hung from the flower until they could manipulate it just right to escape.  Most of the hornets had multiple bags of pollen attached to the spines on their lower legs (which you can faintly see as light yellow oblong structures attached to the end of their leg).



The milkweed’s strategy is to reward the insect with just a drop of nectar so that
it moves to other flowers, gets its leg stuck once again and deposits the saddlebag of pollen in another, different flower and… voila, pollination.

Bumblebees avoided the milkweed preferring the bee balm and the coneflowers instead.  These flowers don’t seem to offer much of a nectar reward because the actual flowers in the composite head are tiny and narrow. However, it turns out that bumblebees have really long tongues, complete with little brushes on the end of them, that enable the bees to reach into a narrow slot and slurp up even the tiniest drop (http://www.bumblebee.org/bodyTongue.htm).  They are pretty hard to photograph close up, because they are continually on the move, testing each flower in the head for
nectar and stopping only infrequently in any one flower for just a few seconds.

Below - bumble bee on purple coneflower:





Above:  bumblebee on Bee Balm (Monarda)

It is due primarily to the services of our local bumblebees that we had such a fine raspberry crop this summer.  In June, the raspberry plants were thick with several species of bees, but the bumblebee, in particular, is an incredibly efficient pollinator.  Apparently they develop electrostatic charge as they fly, so that when they land on a flower, the pollen attaches itself to their fuzzy thorax and leg spines.  When they move on to another flower, the receptive stigma of that flower attracts the electrically charged pollen away from the bumblebee, and again, voila…pollination.  Another amazing feat bumblebees perform to collect pollen (which they feed to their larvae) is to “buzz” the flower at a frequency that causes the pollen sacs on the flower’s anthers to open and dust the bee. The bees groom themselves when they get back to the nest, depositing their pollen for workers to feed the larvae.  However, while out foraging, there is an abundance of pollen on them that finds its way onto theappropriate flower receptacle.  Some people claim that these characteristics make bumblebees far better pollinators than honeybees.

Summer Friends

I know it's mid summer when these little guys make their appearance on my front door.





My whole family enjoys these friendly little frogs - the Cope's Gray Tree Frog. This little guy is one of two almost identical tree frog species in Minnesota - the other being the Eastern Gray Tree Frog, and they are really only distinguishable by their call (which are still very similar), the black markings (or lack thereof) on their backs, and by chromosomal analysis. Since I don't feel like trying to scrape a bit of cheek cells off this little guy (or trying to obtain a blood sample), I am using my expert (not) observational abilities, noting that my friend here does not have black spots on his back, and that his trill is fairly fast (and can be compared HERE), and am therefore calling him a Cope's Gray Tree Frog.

But really, his name is not the most interesting part about this little frog. These are amazing creatures! As would be expected by their name, the Cope's Gray Tree Frog live in trees surrounding wetlands, prairies, grasslands, and Oak savannas. They have been found to hunt at night around lighted buildings on the outskirts of towns or around rural homes (which is why I have them on my front porch in the evening and morning - apparently, the hunting is good by my front door - and is also the reason we have to abandon the spot by mid summer lest we get eaten alive by hungry mosquitos).

The Cope's Gray Tree Frog breeding season is from May to July, and as with all frogs, they require a wetland to mate, lay eggs, and for tadpoles to live in for the first weeks of their lives. This brings us to an important point. Many wetlands in our area are becoming compromised by new homes being built and dirt being filled into them to allow for better building pads, but also by residents of these homes who stock their high quality wetland with fish, because they think that's what's supposed to be there or because they want to be able to go fishing in their own back yard. While fun for the fishermen, this can have catastrophic effects on all the frogs (and other amphibious creatures) in this community. Stocked fish have been shown to predate up to 94% of native wetland creatures, including the Cope's Grey Tree Frog, leaving the wetland a barren, fish filled waterway. The moral of the story here: if there aren't fish in your pond, wetland, or small lake, DON'T PUT THEM THERE. Wetlands are not just a flooded prairie. They are a breeding ground, a sanctuary, and a life giving haven to many of Minnesota's native wildlife, and they are fragile ecosystems that can be destroyed with the slightest human interaction.

Okay, now that I've said my piece on that, I want to share the most interesting part about the Cope's Gray Treefrog...

Living in Minnesota, it gets darn cold in the winter. What's an amphibious creature to do when it gets to be -10 degrees F? These frogs have an amazing ability to produce glycerol - and when it gets cold out, it circulates through the cells to prevent ice crystals from forming. Then, the frog freezes, it's heart stops, circulation stops, the frog stops breathing, and it spend the rest of the winter in a suspended animation state! When spring arrives, the frog slowly thaws, and thanks to the glycerol, all the cells are intact, and the frog heads back up the tree (and into the wetlands) to continue it's life.

How about some more pictures?



I think what I like most about these little guys is that they can change color depending on the temperature. They can go from grey (thus the name), to brown, black, tan, or even green within a few minutes. And the toes! I love their long sticky toes.





They make a mucos on their toes that allows them to stick to nearly any surface - even glass! It makes me happy when I wake up in the morning and see tree frogs crawling up my windows.



If you'd like to read more about the Cope's Gray Tree Frog, there's a great page HERE and HERE. Thanks for reading!

Alien Invaders

Have you seen these in your yard or on the golf course this
summer?



The Japanese Beetle is an attractive insect, but a destructive one. Look what they've done to the leaves of one of my raspberry plants.



The beetle has been in the US since the early 1900s, but occurs primarily east of the Mississippi River in growing numbers.  We seem to have a particularly heavy infestation in the Twin Cities this summer.  Larva overwinter as pupae in the lawn soil, emerge as adults in the spring, mate on various sorts of plants as they eat through its leaves, lay their eggs in your lawn, and the larva grow up feeding on grass roots until they enter a suspended state of metabolism during winter cold weather.   Plants the adults prefer to munch while finding a mate include roses and red raspberries, dahlias, hollyhocks, and hibiscus, and various trees such as Japanese maple (naturally), Norway maple, apple, and Crepe Myrtle, as well as soybeans.  They particularly like fragrant roses; one of my white roses had so many beetles chomping away inside the petals, it looked like it was animated by Harry Potter magic.



How do you get rid of them?  In Japan, they are controlled by their natural predators and parasites, but in the U.S., unless there are huge infestations with risk of crop damage, affected plants are usually not treated.  To read more about its control, go here:

It is also suggested that the best control is to use landscape plants that don’t attract the beetles, like red maple, boxwood, redbud, dogwood, burning bush (Euonymus), juniper, spruce, and pine or flowering perennials like ageraturm, columbine, begonia, lily of the valley, coreopsis, larkspur, foxglove, and hosta.

Welcome!