Fine structure and development of the large sensilla basiconica on the antennae of sphecid wasps

The large sensilla basiconica of different species of the Sphecoidea are similarly shaped. Each sensillum is associated with a large number of sense cells as well as three envelope cells, the second of which is doubled. During early development degenerating supernumerous envelope cells were observed. After the early cell degeneration four envelope cells remain. The inner envelope cell secretes a temporary dendritic sheath, the three outer envelope cells secrete the various parts of the cuticular cone. After the secretion of the cone, envelope cell 3 degenerates.