Larval tongue worms are occasionally found in humans, who
acquire them from other vertebrates, generally from domestic
animals. Pentastome growth in humans is checked, however,
because the nasal tissue responds by forming calcareous capsules
that surround and isolate the worms. Tongue worms range in
length from a few millimeters to more than 150 mm. The digestive
tract is a straight tube. Excretory, respiratory, and circulatory
organs are absent—common adaptations to necrotrophic life.