Under a magnification of 128X, this photomicrograph revealed the presence of two, Strongyloides sp. filariform, larval-staged organisms. Infective, third-stage filariform larvae (L3) of Strongyloides stercoralis are up to 600µm long. The tail is notched (see PHIL 1509, under higher magnification), and the esophagus to intestine ratio is 1:1. Infective L3 larvae are found in soil and invade the human host by direct penetration of the skin.