This is a bald-faced hornet's nest (Dolichovespula maculata). Although they’re pretty well hidden during the summer months, once the leaves fall in the autumn they are revealed up in the bare branches of the trees. In November and December we drive around the city looking for them. They’re empty by then – the wasps only live for one season, and once the cold weather sets in they abandon their nest. The newly-hatched queens look for a place to hibernate for the winter – behind a bit of bark or shingle, or wherever they can tuck in and hopefully survive the cold. Those who are still alive in the spring will wake up and look for a suitable place to begin construction on a new nest. By this time the previous year’s nest has disintegrated – it’s rare to see any signs of a nest in February, for instance. Without the colony constantly working on the growth and upkeep of a nest, it usually falls apart and disappears during the first few winter storms or windy nights. So we need to collect them soon after they’ve been abandoned. Sometimes new inhabitants move in after the wasps have gone. Spiders and ladybugs are the most common new tenants. Often squirrels have hidden a few peanuts inside. There could be holes pecked through the paper by birds looking for insects to eat. Some of the chambers still contain unborn wasp larvae and there may be a few dead wasps between the layers of paper. Perhaps a few queens have tried to hibernate there but it’s not a good choice of places because they don’t last long.

This past fall (2009) we collected 135 nests, all in a relatively small area in the city of Toronto. This was almost twice as many as we’ve ever found in previous years, and there were very many more that we passed by because they were too high or too small or otherwise not choice, according to our own criteria. For some reason there was a part of town where we could predictably find the brownish-golden nests that are favourites to use. We have many unproven theories as to why there are lots of nests in some years and relatively few in others. Sometimes there are many nests but they are generally small. Sometimes there are fewer but they are big. This year they were usually medium to large-sized and there were very many. Weather conditions must play the biggest part in determining the number, size and success of the colonies. A mild winter and early spring means that more queens survive and more nests are begun. A long hot summer may mean bigger nests. And perhaps the month-long city-wide garbage strike had something to do with the abundance of healthy nests and well-fed wasps this year. I'd like to understand more about the conditions that the flourishing or depleting of the species is dependent on. In any case, this year we could count on bringing down at least a dozen within a few hour's work.

Getting the nests out of the trees is an operation that Allen and I specialize in. We have five bamboo poles, each about 8 feet long, which slide in through the back of the car and lie along its full length from the dashboard to the back of the trunk. One of these poles has a strong hook inserted into one end. A full roll of duct tape and a supply of plastic bags are also necessary to bring along. When we spot a good nest, we estimate the number of poles it will take to get it down. A one-poler means a quick job whereas a four or five-poler takes considerably more effort. The required number of poles are brought out of the trunk. One overlaps the next, and the two are taped together in several places. If the nest is in a tree growing in the front yard of a house, we need to ask the tenant if we can remove it, which often leads to some interesting conversation and lots of education about the life-cycle of the wasp and their paper-making skills. If the nest hangs over the street, then there needs to be some traffic-control while the poles are raised and the aerial fishing goes on. If the nest is hanging from one thin branch, then it can be snagged easily by getting the hook around the branch just above it and twisting the poles until the branch snaps. Whoever is down below, not wielding the poles, has a chance to catch the falling nest. This is pretty satisfying when it happens. Often a nest has been built around several branches, one or more of which is too thick to snap, so we call this nest a poker. Rather than hooking it, the end of the pole needs to be poked right into the nest and the whole thing pushed upwards and shaken until it comes apart. These nests come down in pieces. If the nest was high and therefore took awhile to get down, there are often a few people standing around who had stopped to watch the procedure, so sometimes it becomes a social event.

At the peak of summer a successful bald-faced hornet nest may contain up to about 500 wasps. A queen, who was fertilized during the previous season, first builds the beginnings of the nest which consists of one small layer of about seven hexagonal chambers. She lays an egg in each chamber and continues to build the next, larger layer of chambers below this one while the young go through their metamorphoses from eggs to larvae to pupae to wasps. As soon as the first ones chew their way through the silken covering of their chambers, they take over the work of re-building the nest to accommodate the growing hive and of feeding the larvae and queen and generally tending to all the needs of the colony. These are all sterile female worker wasps. As the nest grows, more layers of chambers are added and more of these workers are born. They remain constantly busy. In August the drones begin to be born, along with the new queens who will continue the species into the following year. The drones mate with the new queens while the workers continue to feed everyone and make the paper for the nest’s ever-changing needs. By the end of summer the activity slows down and once the weather is cold all wasps leave the nest. Only some of the new queens survive the winter.

It’s fascinating to watch a worker make paper. She may land on a tree trunk or some lumber, for instance, where she’ll walk backwards while scraping off a layer of cellulose with her mandibles. If you look closely at any unpainted outdoor lumber you will probably see signs of this – many one or two-inch long stripes where the colour of the wood just below its weathered surface shows up. She will chew up this cellulose into a pulp, then fly back to the nest and begin to lay the new material down along the edge of the paper already made. She does this by, again, walking backwards and spitting out the pulp along a row, then several times coming to the front of the line and pushing it out sideways, thereby increasing the paper’s size. Apparently there are properties in the wasp’s saliva which act as a fire-retardant. Once while in the woods I found an empty nest and that night sat near to a warming fire while taking it apart. The dirty bits were thrown into the flames. It was especially noticeable with the combs that once in the fire they did not burst into flame like other paper surely would. They did eventually burn, but with a reluctant smouldering.

So the colourful stripes of a nest are created by the various pigments in the wood or other cellulose that the wasp chews. We’ve collected nests from ornamental or fruit trees that are predominately red. Oak bark also has a lot of red pigment in it, so the nests in some oak trees are often red. It’s common to have bold stripes of white or a golden colour interspersed with a greyish-brown. The colours range from black through many shades of browns and greys to white. Often there will be flashes of pink or very bright colours that may have come from painted wood or coloured papers that the workers chewed up. Bright greens and blues are common enough, although such colours are usually only occasional stripes amidst the more usual greys and browns. Some of the most beautiful nests have a mix of colours which tends to delineate each stripe more boldly. But the subtlety of a shining, almost uniformly silvery-grey nest is also very beautiful. It’s impossible to tell what colour the nest is until it’s removed from the tree – usually it’s too high up to see this. So it’s always a delight to catch one as it falls from above and discover its unique beauty.