The silk glands of adult sphecid wasps, Microstigmus and Psenulus were examined by light and scanning electron microscopy to describe their structure. Silk glands in both genera were classi ed as epidermal glands of the type 3, that is they are formed by one ultinuclear terminal cell. From the terminal cell, one conducting canal runs along the body cuticle. The canals open to the exterior by means of spinnerets. These cuticular structures have different positions and forms in Microstigmus and Psenulus. The similarities in the structure of silk glands and the differences in spinnerets between these two genera con rm previous reports that silk glands evolved independently in Sphecid wasps.