Thursday, July 16, 2009

Bald-Faced Hornets

Nature Watch

By Susan Benson,
CNHM Director of Education

Maybe you have noticed a football shaped nest hanging from a nearby tree, or a new one being built under your roof overhangs, or under your deck or porch. The term "hornet" is often used to refer to many of the wasps that build large, papery nests. The most notable paper wasp in our area is the bald-faced hornet, a species of yellowjacket wasp. These insects have large, black and white, heavy-bodies with white markings on their faces that resemble a bald spot. They adapt well to their environment, showing a remarkable intelligence for an insect so small.

How do they cope with our northern climate changes? Bald-faced hornets are experts at temperature regulation—both heating and cooling. They heat using the best insulation, trapped air. To cool their nest, special workers bring water to the nest, spread it on the nest and then fan it to “air condition.” But how do they make this nest wonder?

The work begins every spring. In each bald-faced hornet colony, it is the females who do the manual labor. Each worker involved in exterior building gathers a mouthful of tree pulp from loose bark, which she works into paper. The paper is made by mixing starch-filled saliva with the wood. The nest is made up of several tiers of cells, or “cartons” and surrounded by a protective layer. Every visit a female makes creates a strip the color of the bark the wasp harvested, which she spreads with her mandibles and legs to dry into paper. As the nest grows throughout the summer, new, wider tiers are added. The wasps must then remove one or more of the inner layers of insulating paper while constructing new sheets on the outside.

Throughout the summer, worker bald-faced hornets guard the nest and collect nectar and arthropods to feed the larvae. Near the end of the summer, female larvae are fed greater amounts of food, allowing them to develop into queens. At the same time, the queen lays unfertilized eggs that develop into male wasps. The males mate with fertile females, and as winter approaches, the wasps die, except for young fertilized queens that hibernate underground or in hollow trees. The nest is generally abandoned by winter, and will most likely not be reused. This is hard work for one season!

Do we need to be afraid of these wasps? Any animal that is feeling threatened will protect itself. Bald-faced hornets do not have a barbed sting, so can deliver a series of painful stings. It is their venom that creates the pain. However, my method when seeing any bee or wasp is to ignore it, stand still, and let it go on it’s way. Many times when we are wearing colorful clothing, we are often mistaken for flowers, and once they discover that we have no rewards, they move on peacefully. However, beware if you disturb their entire nest.

These insects are beneficial as they are pollinators. They drink flower nectar for quick energy while they hunt, while also using the flowers as a hunting ground for smaller insects that are also attracted there. They can be beneficial in gardens since they predate upon insects that damage plants. It is worth taking the time to observe a bald-faced hornet, as you never know what you might have an opportunity to observe!

For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and exhibits, the Curiosity Center and Brain Teasers 2, in Cable at 13470 County Highway M. Also find us on the web at to learn more about exhibits and programs.

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