Symphylans: Symphyla

The soft, whitish bodies of symphylans (sim-FIL-ehns) are long and slender, measuring 0.078 to 0.31 inches (2 to 8 millimeters) in length. The head is distinct, heart-shaped and has three pairs of mouthparts. One pair is fused together to form a lower lip. The antennae (an-TEH-nee), or sense organs, are long and threadlike or beadlike. There are no eyes. The body has fourteen segments. The back of the body is covered with fifteen to twenty-four soft plates. The first twelve body segments each have a pair of legs. At the base of each leg is a short stiff spine and special sac. The spine probably helps the symphylan move through the soil, while the sac probably regulates water and salts in the body. The next-to-last body segment has a pair of projections from which the symphylans produce silk. The last body segment has a pair of long, sensitive hairlike structures.