Summer's end is coming Sept. 20.
Nights are cooler here at the farm, few birds are singing and some have left on migration while others are beginning to migrate in from the north.
Other signs: Fall fruits are ripening, late flowers are blooming and spiders are maturing and laying eggs. It can be an exciting time of year with a great deal of activity in the natural world, even if the marvelous sounds of summer have dimmed.
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Dark fishing spider ball with hundreds of babies.
The cucumber and Fraser magnolia fruits on our farm mature this time of year ands produce numerous red/orange seeds, which are highly attractive, especially to migrating thrushes.
The Fraser magnolia fruit color scheme is rather interesting since the cone itself advertises by color to attract birds from a distance, then the bright seeds direct the birds to a food reward for eating and dispersing the seeds. The seeds also fall from the cones and can be picked up on the ground in a two-stage process of attracting seed dispersal agents. Yet these magnolias are not always appreciated for their excellent food value for wildlife.
The May apple also blooms in the spring but sets fruit in late summer. Plants must have two leaves to bloom and the leaves and green fruit are protected by toxins. The ripeness is indicated by the yellowish color, which is likely designed to attract mammals on the forest floor.
Fact Box
William Dunson, Ph.d., professor emeritus of biology at Penn State University, splits time between Southwest Florida and his farm in Galax, Va. He can be reached at wdunson@comcast.net.
As with most poisonous fruits, they become palatable when ripe. There would be no point in providing a food reward for animals to eat a fruit and disperse the seeds if the result were death or sickness. But it is definitely in the interest of a plant to prevent the eating of the green fruit before the seeds are ripe or to discourage eating any seeds. This explains why the ripeness of fruits is indicated by changes in color and taste, and why seeds themselves are often toxic and remain so inside a protective husk even when the fruits are ripe. They pass through the digestive system of the frugivore unharmed, are dispersed away from the parent plant and are typically stimulated to germinate by this process.
An unusual sight in one of our flower beds, mulched with wood chips, was the appearance of a bright yellow blob, which appears to be the famous dog vomit slime mold. Slime molds are not true fungi. The plasmodium creeps along slowly much as an amoeba does and engulfs its food, which is mainly bacteria. Such a strange organism tends to freak people out but it is harmless and in fact can be eaten, although it is not recommended.
Another creature that freaks people out is the spider, which has few friends. Yet without them we would be inundated with all sorts of harmful insects.
We have considerable numbers of the dark fishing spider, often far from water. This female had a nursery web next to a pond and is tending hundreds of babies. Although humans tend to think maternal care is an altruistic trait mainly found in higher animals, such is not the case. Care of the young is a selfish and quite primitive trait since its purpose is to protect the genetic heritage of the female's progeny.
Baby spiders group together in a ball, presumably for protection, The sheer numbers are similar to a school of fish in that a predator would find it difficult to pick out one tiny spider to attack. The aggregate group of spiderlings may also discourage some predation due to the size of the group.
For years we tried to grow orange butterflyweed without much success since it appears to be a poor competitor if dense grass or weeds are present.
A hay field mown in mid-June apparently released a group of milkweed plants from competition and five clumps of butterflyweed grew began flowering in mid-August, later than the natural stands nearby. They attracted many butterflies, including a male monarch and a female spicebush swallowtail.
Butterflyweed provides nectar and larval food for the monarch butterfly including protective chemicals against predation (advertised by the bright colors), but only nectar for the spicebush swallowtail, which is one of a number of confusing "black and blue" butterflies that mimic the toxic pipevine swallowtail. Birds must have a problem distinguishing the edible from the toxic also - thus providing an evolutionary advantage for this mimicry complex.
An interesting large fly near our wooden outbuildings turned out to be a tiger bee fly, which is unusual looking and has a strange life history. It is a parasite on the large carpenter bees hated by homeowners because they drill holes in houses and barns. So here we have a beneficial fly that is reducing the number of carpenter bees that will emerge from their tunnels. So do not swat that particularly evil-looking fly! Isn't there is a certain satisfaction that even insects are plagued by other insects?
I miss the clamor of amphibians this time of year although I still hear an occasional call from bullfrogs and green frogs. Huge numbers of spring peepers present in the woods are virtually silent. There must be thousands more dispersed all around.
Our many planted arrowwood virburnum bushes have thrived and have now produced many small bluish berries. Birds are fond of these although they are not as obvious as red berries nor do they appear very appetizing. Flycatchers, such as this eastern kingbird, gorge themselves on these berries, despite the presence of numerous insects all around. There is a nutritional reason for this circumstance but I do not know precisely what energetic requirement is met by these berries. I can highly recommend planting them in your yard.
Everyone loves bluebirds because of their beautiful colors and song, and their use of our yards and fields to breed. Their persistence in breeding is impressive; they start early and continue to breed for a prolonged period. In a check of our 24 nest boxes a half-grown baby bluebirds was likely the last of perhaps three broods their parents produced this year. Yet the tree swallows that compete for the same nest boxes/cavities generally have only one brood in this area. Why are such different strategies successful in the same habitat?
