A: Thank you so much for bringing me a black and yellow mud dauber, Sceliphron caementarium. This attractive wasp can be found from southern Canada to Central America and the West Indies. It has a very distinct, long pedicel or waist attachment which is between the thorax and abdomen. The pedicel can be nearly twice as long as the abdomen. The wings of the black and yellow wasp are amber or smoky in color. The legs of this insect are black and yellow. The pedicel can be black or yellow but it will form a small yellow spot where it attaches to the top of the abdominal area. The black and yellow coloring tells other predators this insect should be left alone. The adult females collect mud for their nests, thus the name, “mud dauber.” Each adult female wasp will build a nest of about 25 cylindrical cells or more at a sheltered location, such as the eaves of the house, in a barn or shed, or under a bridge. She will lay one egg per cell and insert a spider for the larva to consume once it has hatched; then she seals the cell with mud. While all wasps can sting multiple times, black and yellow wasps are generally gentle in nature and not easily provoked. We do not recommend poking them or handling them but as a rule – they are not aggressive. I know people do not often like so see the mud cases on their homes, but if possible, consider leaving them alone. Because they are hunters, we consider them beneficial. The adults also feed on nectar from local flowers.