Fuxian Lake insect is a unique species in the Devonian Chengjiang fauna, which belongs to the primitive type of true arthropods. The adult is 10 cm long and has 31 body segments. The exoskeleton is divided into three parts: head, chest and abdomen, and the number of dorsal and ventral segments is different. Devonian straight shrimp is the ancestor of modern insects, and the fossils of insects in Fuxian Lake are similar to those of straight shrimps, which indirectly indicates that the insects in Fuxian Lake are the distant ancestors of insects. The researchers also found that the digestive tract of the Fuxian lake worm is full of sediment, indicating that it is a mud-eating animal.
The distant ancestors of insects also had creatures that did not eat mud is the only option that cannot support the above argument.