NATURE NOTES: Autumn’s final frenzy

By LESLIE BISHOP, guest columnist

October in the natural world brings a frenzy of activity. With daylight decreasing and temperatures lower at night, it is a time of transition. Just as we are busy cleaning up our summer gardens, many insects are completing their short lives and preparing for the new generation. Others are preparing for winter.

Yellow jackets and other wasps are no exception. These social insects become especially aggressive in autumn — for a good reason.

The number of individuals in a nest reaches its maximum number before frost. Although they may occasionally sip nectar from flowers or ruin a picnic by attacking open soda cans, wasps are carnivores that primarily eat other insects.

The workers are now busy collecting insect prey to feed the last developing larvae in their nests. Many of these last larvae will develop into new queens and males, who will mate before winter sets in.

The survival of these last larvae thus ensures that new colonies develop next spring. Once cold weather comes, all remaining individuals of the colony die, except the queens, who survive to overwinter.

We fear these aggressive insects because of their painful sting, but we can also be grateful to them.

In our gardens they serve as effective insect predators and reduce our need for insecticides. Wasps typically prey on caterpillars such as corn earworms, armyworms, cabbage loopers and tomato hornworms. They also relish the beetle larvae that munch on our green beans, as well as aphids that plague many crops.

All summer I watched a bald-faced hornet nest develop in the corner of our garage window. The nest grew from a small paper ball to a beautiful nest the size of a football sculpted intricately to fit with the window, frame and stones of our home. Luckily the window is not near an entryway, and we could watch their behavior from a safe distance.

These are not true hornets, but are more closely related to yellow jackets, which build large paper nests underground. And similar to yellow jackets, they can sting multiple times while defending their nests.

Bald-faced hornets are large black wasps with white or pale yellow on their faces and the tips of the abdomen; they are quite distinctive in appearance from yellow jackets and other wasps.

In the spring, a new bald-faced hornet queen, who mated the previous fall and overwintered alone, begins the new colony. She produces paper by shaving wood from posts or boards in strips with her strong jaws (mandibles), chewing it thoroughly and mixing in saliva to produce a paper pulp.

After she has chosen a place to build the nest, she uses the paper pulp to make a stem that supports the first horizontal layer of hexagonal cells. She will lay her first brood of eggs in these cells. She covers the nest in a protective shell composed of layers of paper.

The eggs hatch into grub-like larvae. The queen captures caterpillars and other insects, chews them up and feeds the mash to her developing larvae.

These larvae undergo metamorphosis and emerge as female workers who take over the business of nest building and prey capture. The queen is now free to do her main job — egg laying — for the remainder of the summer.

As the number of workers in the nest increases, so does the size of the nest. New horizontal layers are added by connecting them with paper columns to the layer above. The nest grows from the top down into a multistoried complex. Not only can the nest grow in length, but also in width as workers add laterally to existing floors.

As the nest grows, the protective shell that covers the entire nest must also grow. You can watch hornets (from a safe distance!) building these outer walls. They bring pellets of paper pulp back to the nest one after another, and spread them in strips with their mandibles by walking backwards.

The color of the strips reflects the type of wood used: gray from weathered fence posts or red from decaying oak wood.

The patterns of the colorful strips on the outer walls of wasp nests create one of the most artistic structures in the insect world. These nests have attracted the attention of naturalists for centuries. In fact, observations of wasps’ paper making inspired the shift in 18th century Europe from using cotton and linen rags to employing wood in commercial paper making.

Now is the time, on these last days before a hard frost, to get out and observe insects and other animals that are making the last preparations before winter. Maybe there are other lessons we can learn from the innovative work of insects.

Leslie Bishop is a Brown County resident and retired biology professor from Earlham College. She is a volunteer interpretive naturalist at Brown County State Park. She can be reached through the newspaper at newsroom@bcdemocrat.com.