Vespula is a genus holding a small number of social wasps. With the sister genus Dolichovespula, these groups are jointly termed yellow jackets. There are over 200,000 species, but the yellow jackets only make up a minor proportion of this, amounting only to 1 per cent in total. It's these wasps that you may see lurking near picnics, falling into drinks and just being a general bother. You should try to tolerate these insects if you can. By squashing them, you can attract more wasps. This is a defence mechanism that's initiated by the pheromone (odour particle) released when a wasp is squashed. They provide an array of services in the wider ecosystem and its thought that they do a considerable amount of pest control. There have been over 6,000 species of solitary and social wasp recorded in ZA.