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27 Jun

keywords: milkweed, June beetles, meadows, flowers

June meadows receive a heavy dew, breath a thick mist, and, in their flowers, display the royal colors of gold and purple.

Legumes (that is, members of the pea family) are common in our hayfields and pastures, because their nitrogen-fixing abilities make them good as both soil builders and as animal forage. This ornate splay is the European Cow Vetch.

Another popular legume is Red Clover. It is probably our most common field legume. In many cases, the fields are 'frost-seeded' with legumes. That is, the clover seeds are spread over unploughed ground late in the winter, and the seeds work their way down during the usual heaves and drops that accompany soil freezing and thawing.

Deptford Pink. Another European species, oft described as a weed.... an elegant weed.

A yellow-legume, Bird's Foot Trefoil, to add to our purple-flowering nitrogen fixers. (Nitrogen fixation is actually only an in-direct product of these plants - their roots make happy homes for certain bacteria which then do the actual biochemical work of taking nitrogen gas from the air and converting into a form that plants can use.)

Sulfur Cinquefoil. Unlike the legumes first shown, species like this and the Deptford Pink were probably not intentionally introduced into the fields. In some cases, they just came along for the ride in manure, ballast dirt, plant pots etc that were brought over from Europe. In other cases, they were planted in flower gardens and then struck out on their own.

This is a European Buttercup, a frequent resident of our fields and lawns. There are native Buttercup species, but this isn't one of them.

As a transition of plant to bug, here's a Milkweed Beetle hanging out on Milkweed buds. Note the similar coloration between this and the Monarch. Bright red may alert potential predators that such insects are packed with a bad mouthful of chemicals and are best left alone.

Milkweed in bloom. The Honey Bee (also from the Old World... but the Milkweed is not) is out of focus because it was quite agitated. With good reason... its foot is caught in the milkweed flower and so begins our tale.

The previous week, at a site in Dutchess County, I had noticed these small European Skippers dangling from a Milkweed flower. Often such flower-trapped insects turn out to be the work of crab spiders which hide out in the blossoms and ambush unsuspecting visitors. But in this case, it was the flower itself who was trapping the prospective pollinator.

This picture leads us a bit closer to an explanation. The leg of this fly can (more or less) be seen inserted into a slit located between the two petals.

Here's a close-up of the Milkweed flower, with the petals parted slightly to show the slit between them. At the top of that slit, the black speck is the structure that holds two pollen sacks together. Picture an insect that has poked its leg into the slit while trying to get a grasp on the nectar-rich flower.

As the insect pulls its leg out of the slit, it catches on the notch in the black structure. Its struggling begins to pull the pollen sacks (the yellow structures in the picture) out of the slips where they have been resting.

Continued struggling pulls the pollen sacks farther out of the flower until, finally, ...

the insect flies away with the pollinia grasping its leg (OK, so this isn't the bionic fly, it's my tweezers, but I hope you get the picture.) However, the story is not over yet...

Then, like this ant, the visitor is stuck with pollen spangles on its feet. The plant has done half its work...

If the be-decked flower-visitor continues to visit Milkweed flowers then, sooner or later, one of its dangling pollen sacks (called pollinia, singular=pollinium) will slip into another flower's slit and get caught, as has happened here. I did not pluck this leg from an insect. Often, unable to remove their leg or break-off the pollinium, the insect jettisons its leg, leaving it behind to adorn the flower.

Here, I have moved the un-fettered pollinium to one side, so that one can better see the trapped one.

This last picture comes from the partial dissection of a Milkweed flower that had no obvious insect parts attached to it. Lying inside of almost every slit was a detached pollinium as shown here. Importantly, also inside of each slit are the flower's stigma - the female receptacle for the pollen. Once a pollinium as become trapped in a stigmal slit, it apparently hydrates with nectar and eventually the sack dissolves and the pollen fertilizes the flower.

Craig Holdrege of the nearby Nature Institute has written a very nice description of milkweed including a description of the pollinization process. Click here to read his interesting account.

To close, just a few more invertebrate miscellania. Move the plant stalks aside and get to the ground surface of the meadow, and you'll probably see a spider or two scurrying across the surface. These are Wolf Spiders, a family of spider which hunt their prey not with a web but by the chase. They do, however, make silk. As this mother spider illustrates, they use it to wrap up their egg mass into a handy purse which they carry about underneath them.

This mass was dangling below an elm leaf that overhung the Farm Creek. What was this furry spot?

Looking more closely, it turned out to be a swarm of little heads looking up at me. These are probably alderfly larvae which have just hatched from an egg cluster that had been stuck to the leaf and which was barely visible beneath their feet.

For Charley Eiseman’s recent alderfly blog, including upclose pictures of the little ones, checkout this link

May (or June) Beetles (or Bugs) are fairly large beetles that often come to lights during this time of year. For a while, a few weeks ago, they seemed particularly abundant.

Such abundance doesn't often go unnoticed in the biological world. Gisela and Michael-James showed me this "light fly" that they had caught . Apparently, this fly parasitizes adult June beetles, ovipositing on the beetle as it flies (when the soft parts are exposed).

Finally, this is a "Ichneumon annulatorius" wasp, not that that tells us much. Apparently, it is known to parasitize Army Worms. Some wasps, if not this particular one, are parasites on the larvae of insects such as June Beetles.

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2 Comments

Posted by on June 27, 2011 in Nature

 

2 responses to “

  1. Amy Lou

    July 13, 2011 at 10:42 pm

    Conrad you are amazing…I am so glad that Tom & Adelia forwarded on your blog to us. The descriptions and photos are beautiful. We kayaked through Drowned Lands and thought of you and Otter swimming around finding all sorts of treasures. Much love Amylou, Finn, Addie & Cosmo

     
  2. Judy Anderson

    June 29, 2011 at 10:16 am

    Hey, great photos, and I love the fly story with the “illustrations” and then explainations.

     

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