All things bright and beautiful,
All creatures great and small
All things wise and wonderful,
The Lord God made them all
Mrs C.F. Alexander (1818-1895).
Wasps, and the wasp season has just begun, can be a problem even to nature lovers and, since insects thrive in warmer rather than colder climates, Rome is full of them. Two questions arise: what is the use of wasps and why are they so successful?
Wasps belong to the insect order Hymenoptera (membranous wings), along with ants and bees. They are social insects and live in large communities where every individual has a role to play from birth to death. A completed wasps nest is an ovoid structure usually about 50 cm in diameter, although in New Zealand, where European wasps have been introduced, huge nests of over four metres in diameter have been recorded. In the spring fertilized female (queen) wasps emerge from hibernation and set off to find a suitable nest site. Usually an underground cavity such as a rabbit burrow is chosen, but hollow trees and cavities in walls may also be used. The queen rasps off thin layers of old wood from fence posts and such and chews them, with saliva, into a kind of wood pulp. This is worked into shape and becomes wasp paper. The queen constructs a dome from which is suspended a stalk attached to a group of hexagonal cells. An egg is cemented into each cell and after a few weeks of care and feeding from the queen these give rise to the first wave of workers. The workers take over nest building and feeding duties from the queen, who devotes the rest of her life to egg laying. New layers of egg cells are added as the community grows, and foraging for food becomes the main activity of the workers. Unlike bees, wasps, in the larval stage, are carnivorous, which is why they are so useful to humans. The workers cruise the neighbourhood trees and other plants looking for, and carrying off, small insects which are chewed into a pulp to be fed to the growing grubs in the nest. The grubs accept this food and, in return, exude a sweet liquid which the worker needs to replace lost energy. In this way wasps are responsible for removing countless millions of insect pests which would damage agricultural production in no uncertain way.
Adult worker wasps need only sugars to keep them going (they are no longer growing and do not need protein). This is where they become a nuisance, as they attack fruit, jams and sweet drinks. Wasps are equipped with a very effective means of defence in the form of a sting which is, in fact, a modified ovipositor or egg-laying instrument and is supplied with poison glands. The actual poison is a complex mixture of proteins and histamines and can cause quite serious allergic reactions in some people, apart from more or less intense pain. On top of that, the wasps sting is not a one off affair as it is with bees. The sting can be used over and over again to give multiple wounds. It is important, therefore, to avoid disturbing wasps as they go about their business. Children in particular should be trained always to look before biting into a sandwich or sipping a drink. A sting on the lips or inside the mouth is a serious, very painful matter. Wasps alighting on clothing or on the skin should be gently coaxed into leaving rather than subjected to panicky, brusque movements. They usually respond by leaving quietly.
Hornets, huge wasps which are a brown/yellow rather than the wasps black/yellow colour, are much more common in Italy than in northern Europe and therefore potentially much more dangerous. They tend to favour hollow trees or empty buildings for the construction of their huge nests. Fortunately, hornets seem to be much less invasive of human activities than their smaller cousins, but they should be respected and avoided since their sting is very potent.
A final word about a rather different insect, not a wasp but a bee the carpenter bee. This insect is the large, shiny, blue/black bee which we see all through the spring and summer as it searches flowers for nectar and buildings and trees for suitable rotten wood in which to build its nest. This fearsome-looking creature does indeed carry a very potent sting but it is very reluctant to use it, and one would actually have to handle the bee roughly in order to be stung. So watch carpenter bees, admire their beautiful wings and colours to your hearts content. As long as you keep your distance you are quite safe.