Time of Plenty by Heather Doherty was originally published in the BFEC newsletter, Vol. 19/No. 4, Fall 2015.
Early fall is the time of harvest, when we celebrate a wealth of fruits of the soil. Many corners of our natural world also find their fullness in fall, from the expected acorns and woolly bear caterpillars to unexpectedly goulash spiders.
One of my neighbors spends her evenings softly cursing the natural abundance that rains down on her deck. Her children sled, literally, down a steep hill below on hickory nuts from an impressive tree in the backyard. Their abundance is worthy of ankle twisting in a wide perimeter around the house.
While this particular bounty is more appealing to wildlife, we humans take our harvest seriously too. In late summer, our stomachs burst with dinners of corn on the cob and a profusion of garden tomatoes. To a person who loves her fruits and vegetables, the volume and array of the selection is a short-lived dream. The dream is already slipping away as I write this article, but the largess is still underway outdoors.
Many plants let loose their bounty in fall months before entering dormancy. Grasses in the BFEC prairie nod their heavy seed heads in the breeze, while plumes of milkweed seed drift like feathery bubbles.
Maple trees send their helicopter seeds (known officially as “samaras”) whirling haphazardly downward, while black walnuts fall with a heavy thump to blacken the ground below. The sub-pea sized fruit of black cherry trees or the red seeds of dogwood that quickly fall or are consumed by birds are more easily overlooked.
Of tree species, the mast of oak trees — acorns — are surely the most well know, and are dearly sought by wildlife. In addition to squirrels, they are greedily devoured by deer, wild turkey, woodpeckers, blue jays, ducks, foxes, raccoons and insects.
The wealth of acorns coating the ground under a mature oak tree can be astonishing. But annoyed homeowners likely revel in the fact that acorns do not rain upon them every year; most species produce a large crop of acorns every two or three years, and a truly massive crop even less frequently. The cycle can be affected by factors like drought, a late spring frost that shrivels oak flowers or the tree’s general health. Regardless of such complications, oak trees alternate heavy mast years with years of measly production.
Why the “go big” or not-at-all strategy? Producing an abundant crop of acorns consumes a large share of the tree’s energy that it simply can’t afford every year. And even though acorns are not considered “prey” in the usual sense, the theory of “predator satiation” may also apply here.
This theory suggests that rather than spitting forth offspring one a time to be gobbled by a throng of hungry creatures, a given species may wait to release all of its young at once, creating such an overabundance that a few actually escape after predators have rolled away from the table.
You can see this theory in action on the shores of Lake Erie when millions of mayflies, which have been living as larvae underwater, emerge en masse to coat every surface of nearby towns. With abundance so tremendous that cars skid on them like ice when they accumulate on the road, a few manage to evade the gorging bats, birds and fish to mate and lay eggs. (Tomatoes may operate under the same guise, when they fall to the ground after diligent gardeners grow weary of the daily tomato menu and heat and weeds.)
While heavy, alternating mast years is one form of self-preservation for oak trees, they do have another: tannins. These compounds are abundant in acorns and can disrupt an animal’s ability to effectively digest proteins. While the bitter tannins can make cows or horses ill, plenty of birds and mammals eat them anyway. Animals such as white-tailed deer seek the lower-tannin species of the white oak family, while others have been observed caching acorns and consuming them at a more moderate rate.
People have been known to enjoy this and many other wild-nut bounties too. Native Americans consumed acorns after repeatedly soaking them to remove the tannins and then pounding them into flour.
Non-nature enthusiasts may be alarmed by a big fall migration... not of birds heading to Central America, but of creatures seeking shelter in the warmth of our homes. Among the unwanted guests are spiders. If not indoors, fall is the time for near-spider experiences while walking around the yard or on trails.
Scores of tiny webs scattered in the grass and on the BFEC’s split rail fence shine with dew in the morning autumnal sun. A less appealing version is finding yourself face-to-face with a giant spider, realizing that you were very, very close to walking through the web and wearing the spider as a new hair ornament.
Not a welcome surprise to most of us, though the spiders are spectacular. Why do these beauties appear in fall, just in time (coincidentally?) for the season of ghosts, jack-o-lanterns and headless horseman?
The lifecycle of some spiders follows the same schedule as the innocuous acorn. Way back in spring, tiny spiders hatched from eggs, perhaps just as subtle flowers dotted oak trees. The young spiders, like the tiny new acorns, were initially easy to miss. But by the end of the season, they make themselves known in all of their substantial glory.
This cycle applies to the sounds of the season too. It’s not until mid to late summer that nights fill with the songs of crickets, grasshoppers, and katydids. While birds and frogs jubilantly sing the rites of spring, the young forms of these insects bide their time, eating leaves, growing and molting, and waiting for their moment. As the birds tire, the insects reach their own maturity and begin to sing.
FUN FACT: the rate of a cricket’s chirps per minute correlates directly to temperature, which is why those chirps become very slow as the season advances. Once the ambient rate of a species is known, it is possible to count its chirps and work backwards to determine temperature.
Though not all spiders mature in late summer and fall, it is true of one of our most conspicuous species, the black and yellow garden spider (Argiope aurantia). It is a member of the orb-weaver family, named for their wheel-shaped webs. This species builds webs that are two to three feet wide, with a prominent zig-zag of silk in the middle.
Their preferred habitat is tall vegetation on the edge of fields and in gardens, and sometimes the eves of adjacent buildings, making them common human neighbors. Unlike other nocturnal orb-weavers, this species is active during the day, and makes a habit of resting at the center of its web rather than in a hidden refuge. What’s truly unmistakable, of course, is its 2.5 inch leg span and bright black and yellow markings.
True to many spider species, the females are much larger than the males. Males build smaller webs nearby and attempt to ward off other suitors. They court females by plucking strands of her web; males die soon after mating (and yes, are sometimes consumed by the females). Females produce egg sacs that they suspend near the center of their webs to be guarded, but only for so long. Females will die near the time of the first hard frost, and spiderlings emerge in the spring, noticed at first by no one but their tiny prey.
The coincidence of spider splendor and Halloween seemed way too great during the BFEC Harvest Festival last fall when student intern Caitlin Redak spotted a real beauty — the marbled orb-weaver (Araneus marmoreus). The very round body of this spider, about 3/4 inch in diameter, was bright orange with darker orange markings, a coloration that appears only as it matures in October. The spider looked decidedly like a Halloween jack-o-lantern.
This season is also the hour of the caterpillar. On warm days they seem to be everywhere, crossing paths in a very business-like hurry, seemingly unbothered by people pausing to exclaim over their colors and tufted, spiky hair. At this time of year, after spending months in treetops or shrubs consuming leaves, caterpillars are likely looking for a suitable place to over-winter.
Through the winter, they will exist in a state of diapause, developmental stand-still. Diapause is triggered by environmental stimuli, in this case shortening day length.
Those caterpillars that are destined to become moths will look for shelter in a brush pile or leaf litter on the forest floor, or even dig a few inches in loose soil, and then form a pupae (similar to a butterfly’s chrysalis). The shorter days had already signaled to the caterpillars that they should stay put through the cold weather.
I observed a tomato hornworm plucked from one of my tomato plants last September in this process. I put it in a container with several inches of soil, where it eventually dug down and formed its pupae. Had this occurred in the middle of summer, it would have spent about two weeks there and then emerged as an adult moth (with an impressive three inch wing span). Since it was late in the season, however, the moth had been triggered before entering its pupae that diapause and a long wait underground was its course of action.
Now buried underground, insects like this one must also avoid freezing to death. Similar to amphibians that also spend the winter in leaf litter, some insects avoid freezing by secreting their own “antifreeze.” Known as cryoprotectants, these molecules lower the freezing point of an insect’s body. Some insects also develop an ability to limit freezing to certain tissues in which it causes less damage.
Though the tomato hornworm posses a rather intimidating horn on its rear end, it does not actually sting. But beware of other seemingly fuzzy caterpillars, for some of them, like the caterpillar of the gorgeous io moth, actually posses stinging spikes.
The adult io moth is adorned with two very prominent eyespots on its back wings (presumed to emulate owls and scare off birds), on a field of rosy pink or yellow. It’s beauty is short lived, since it has no feeding mouth parts. All of the eating it will ever do takes place during its larval stage.
Unlike some other moths and butterflies, it is not picky about which plant species, or “host,” it will choose to lay its eggs on to become food for the nibbling larvae. Its selection includes red maple, dogwood, beech, ash, oak and many others. I was surprised a few months ago to find a cluster of them feeding on cattail next to a pond. By now, they are likely already curled up for winter as pupae, bidding their time until spring.