Mud cocoons are constructed by Sceliphron wasps. Also called mud dauber wasps, they are long and slender insects, with a narrow thread like waist. Their color is blue or black, with yellow markings.
Only mother wasps construct nests. The nests are built usually under bridges, inside caves, on the walls of barns, car ports, underside of barks and places that are safe from rain.
The nest shape and design vary. Black and yellow mud dauber builds a pot shaped nest, the size of a lemon. Organ pipe dauber builds half-inch wide cylindrical tubes resembling pipe- organ pipes. The nest consists of a number of cylindrical cells, each separated by a partition.
Before building a nest, the mother wasp finds a place with moist clay soil. She collects mud with her mouth. Rolls mud into a ball and carries to the nesting spot. There she molds the mud ball with her mandibles. One mud ball against other are smashed every time. The saliva from her mouth acts as a glue. She makes a series of cells with partitions in-between. All the cells are plastered with a final coating of mud, to form a smooth nest.
The mother wasp works hard the whole day from morning till sunset. She rests at nights. She takes unto two days to complete one cell. As she flies close to nest, the buzzing sound she produces comes from the fast beat of her wings. She fans the mud to dry out quickly.
When the nest is nearing completion, the mother wasp goes hunting after spiders. She prefers jumping spiders, catches and paralyses them by her sting. She brings them to the nest. Each cell is filled with five or six spiders. She lays a single egg on the spider bed and seals the cell with mud. After she has completed a series of cells, she leaves the nest for ever.
The egg inside a cell hatches into a larva. The larva has plentiful spider food kept ready by its mother. The larva wastes no time. It feeds and grows. Soon it becomes pupa and undergoes development. The cell serves as a cocoon.
After nine months, adult wasps emerge out of the nest, making large holes. It is spring time and the adult wasps have plenty of nectar available. It is interesting to see that while the adult wasps are nectar feeders, the larvae are spider eaters!