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Posts tagged “Pollination

Common Milkweed Pollination

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The structure of the Common Milkweed (Asclepias syriaca ) flower is such that its pollen, produced in two saddlebag-like sacs with a black appendage joining them, snaps onto an insect’s leg when the two come in contact with each other. To assure that the chances of this are high, the pollen sacs (pollinia) hang inside a slit that is located between each of the five cups, or hoods, that contain nectar. An insect lands on the slippery flower, attracted by both the scent and availability of nectar, and inadvertently one or more of its six legs slips down between the hoods into a slit, where the pollinia automatically attach to the leg. The insect withdraws the leg upon leaving to find more milkweed nectar, and the attached pollinia eventually falls off onto another milkweed flower, pollinating it. Unfortunately, about 5% of milkweed flowers visited trap insects because they cannot extract their legs from the slit. It is not uncommon to see an insect dangling from a Common Milkweed flower – during a 30 minute visit to a milkweed patch recently I released 2 flies, 3 skippers (butterflies) and one honeybee that were caught, but hadn’t yet perished.


Hummingbird Clearwing Moth

Of all the insects I’ve found in milkweed patches over the years, the Hummingbird Clearwing is one of my favorites. It is a species of sphinx moth, named for its habit of hovering at flowers while it gathers nectar with its proboscis in a manner similar to that of hummingbirds. In fact, they are often mistaken for hummingbirds. The transparent wings, light brown thorax and dark chestnut abdomen are the field marks to look for. A diurnal moth, the Hummingbird Clearwing can often be found during the day in milkweed patches.


Milkweed Visitors

Milkweed is in full bloom right now, presenting the perfect opportunity for young and old alike to discover the multitude of butterflies, beetles, bees and other insects that are attracted to these magnificent flowers. If you visit a milkweed patch, don’t leave before getting a good whiff of the flowers’ scent – one of the sweetest on earth. How many of the insects you find are carrying milkweed’s yellow pollen “saddlebags” on their feet? You might want to check out my children’s book, MILKWEED VISITORS, which I wrote after spending the better part of one summer photographing the various insects I found visiting a milkweed patch. ( http://basrelief.org/Pages/MV.html )


Blue-eyed Grass

It’s easy to miss Blue-eyed Grass (Sisyrinchium angustifolium), as its flower is only about ½” in diameter and the plant only reaches a height of six to twelve inches. Blue-eyed Grass is a member of the Iris family, not, as its name implies, a member of the Grass family, although it does have stiff, grass-like leaves. Dark lines on its petals and sepals may well serve as nectar guides, leading pollinators to the yellow center. Each blossom is open for only a day at most. Typically you find Blue-eyed grass growing in sunny, wet fields, often on elevated soil — Thoreau noted that if you followed Blue-eyed Grass through a wet meadow, you could keep your feet dry.


Pitcher Plant Flowers

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The Pitcher Plant (Sarracenia purpurea) is a well-known carnivorous plant of bogs. It gets some of its nutrients by trapping and drowning prey in rain water that is caught inside a modified leaf that forms a cup. While most people are familiar with the leaves of Pitcher Plants, unless you visit a bog in June, you’re not likely to see their unique flower. It is curved over when it’s mature and its sepals (modified leaves that protect the bud and are located above the petals in these photographs) are red-purple and pointed; the petals are red and rounded. An approaching insect would be guided into the flower between two of the sepals–it would land on a petal and climb into the flower onto the umbrella-shaped stigma (the sticky top of the female pistil) which I inverted in one photograph in order to show the male pollen-producing stamens. An insect entering the flower would brush against the stamens, collecting pollen on its back while pollen from a previously-visited Pitcher Plant would fall off the insect onto the sticky stigma on which it was standing, pollinating the flower.


Fringed Polygala

Fringed Polygala (Polygala paucifolia) looks a bit like a miniature orchid, but it is not — it is in the Milkwort family. The structure of its ¾-inch bright magenta-pink blossoms is well-suited for its bumblebee pollinators.  The bee lands on the pink fringe at the front of the flower and its weight triggers the white “keel” to drop down.  A slit at the keel’s top opens, exposing the reproductive parts of the flower.  Pollen from the stamens is rubbed onto the bee’s hairs while it probes deeply into the base of the flower for nectar, while pollen from a previously visited Fringed Polygala is scraped off onto the stigma, where it needs to be in order for fertilization to take place.

 


Red-necked False Blister Beetle

 

If you find a blossoming Trout Lily in the woods it is quite likely that you will also find one of its most common pollinators, the Red-necked False Blister Beetle (Asclera ruficollis), on it. Ardent pollen eaters, this group of beetles obtain their common name because many species cause blisters when pinched or squashed against skin. Adults mate on flower heads during pollen feeding. Both sexes feed on pollen, which acts as an attractant, but the female will not accept the male until her gut is packed full of pollen. She stores the pollen in a special intestinal sack in which an enzyme causes the pollen to partially germinate — this causes the indigestible covering of the pollen grain to rupture. She then digests the contents of the pollen grain, which she uses to manufacture eggs.