Oct 14, 2010


by: Lorraine Julien

It was early September and, as I left the house, something caught my eye way up in one of our maple trees. It was a huge hornet’s nest about 30 feet up in the tree - so high that I had to use my binoculars to see it in any detail. The colourful patterns on the nest were amazing and, since it was so far away, I didn’t worry about being stung. The nest appeared to be about 24” long with swirly beige stripes on it unlike any other hornet nest I‘d seen.

Good thing I photographed the nest because just a few days later – about mid-September, some activity near the nest caught my eye. This time there were several ravens or crows (too far away for me to tell which) and they appeared to be attacking the nest. They succeeded in cutting away the outer shell so that it eventually fell to the ground, leaving only some comb sections still attached to a tree branch.

Though not my favourite thing, I did some research into hornet (wasp) nests and they really are a true miracle of nature; the building method has passed from generation to generation for millions of years.

A queen wasp begins construction of the nest by making a stalk from a type of wood pulp. The stalk is attached to a branch or some other structure (like your house!) and then construction begins on a comb. Once the nest reaches the size of a walnut, female workers then take over the rest of the construction. The end result is a super-lightweight structure that enables the inhabitants to maintain a steady temperature of about 29 degrees Celsius well into late fall. This is the ideal temperature to ensure survival of the wasp larvae.

Scientists have been intrigued for years by the lightweight yet strong construction of hornet nests. The nests are made entirely from a type of paper pulp. Unlike honey bees though, wasps cannot produce wax but instead create a paper-like substance (similar to paper mache) mainly from wood pulp. Wood fibers are gathered locally from rotting wood, which is softened into a soft paste by chewing and mixing with saliva. The saliva acts as an adhesive and dries very quickly. The pulp is also used to make combs (much like honey bee combs), only these are used for rearing wasp larvae. The pulp is also used for the insulating, protective shell. The colour of the nest is determined by the type of wood that is used for the pulp. Wasp nests are continually being enlarged during the summer months, as space is required, hence their large size near the end of the season.

Hornet nests are amazing feats of engineering. It’s been found that the nest envelope contains air voids that slow heat transfer, providing insulation and retaining warmth for the young wasps. On hot days, by contrast, large quantities of excess heat have to be extracted from the nest to prevent overheating. When overheating threatens, hornets sit at the entrance to the nest and use their wings as fans to increase the air change rate and extract heat from the interior of the nest, much like an exhaust fan! Also, the wood-based nest fabric takes up moisture from the air at night thereby releasing warmth, through the heat of condensation to the nest interior. The reverse happens in the daytime.

These findings may lead to new applications in timber engineering. Some options include refinements to breathing multi-layered building envelopes and a better use of the properties of wood as a climatic buffer which may moderate undesirable fluctuations in the interior of buildings.

Though there are well over 100,000 species of wasps, I believe this nest was probably built by a large colony of yellow jackets. Yellow jackets do tend to produce larger nests and they are one of the most common and numerous wasp species.

For every pest insect there is a predatory wasp species and, believe it or not, these insect predators actually do a lot of good. During the summer months, one colony can consume hundreds of pest insects every day. In fact, wasps are so good at eating insects that some farmers use wasps for natural insect control. Wasps seem to have little negative impact on farm crops.

Old nests are never resettled the following year as they seldom survive our winter weather. By late September most wasps have vacated the nest – some will die and others will find a spot to lie dormant for the winter and begin the process all over again the following spring.

The next time you spot a lowly hornets’ nest, just think about the engineering and design that went into the building of it - that is, before you run away!

 

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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