Tlie subphylum is called Uniramia because of the presence of unbranched appendages. These animals have non-jointed mandibles, uubranched appendages without any palps. They have only a single pair of antennae that correspond to the second ceplialic segment (second antennae). Malpigliian tubuless act as excretory organs. This symphyla has 10, I300 species belonging to classes Chi lopda, Pauropoda, Symphyla and Insecta.

Pliylum Onychophora wit the s.ingle example Peripatus has a unique position showing affinities with annelids, arthropods and molluscs.