Arthropods are named for their jointed appendages.
Both nematodes and arthropods possess an external covering, or cuticle.
Some nematodes are parasitic on humans.
Arthropods possess an open circulatory system.
Both nematodes and arthropods must molt in order to increase in size.
The ecdysozoans include nematodes, arthropods, and other phyla that have tough external coats, or cuticles, that must be shed as they grow. This process of shedding, or molting, is called ecdysis.
Nematodes, or roundworms, are unsegmented pseudocoelomate worms that lack a circulatory system. Although most nematodes are free-living, some well-known nematodes, such as hookworms and pinworms, are parasitic.
Arthropods have a reduced coelom and an open circulatory system. Arthropods have segmented bodies that enable specialization of body structures such as appendages.
A. hard forewings protect membranous hindwings
(Coleoptera, Wing characteristics)
B. hindwings reduced to stabilizers
(Diptera, Wing characteristics)
C. wings have scales
(Lepidoptera, Wing characteristics)
D. hairy wings
(Trichoptera, Wing characteristics)
E. complete metamorphosis
(Hymenoptera, Type of Development)
F. incomplete metamorphosis
(Orthoptera, Type of Development)
H. "true bugs"
I. butterflies, moths