Armored Harvestmen

Photo of an armored harvestman walking on the ground
Scientific Name
Libitioides spp.
Family
Cosmetidae, in the order Opiliones (harvestmen), in the class Arachnida (spiders, scorpions, mites)
Description

Armored harvestmen have spines on their fingerlike mouthparts (pedipalps). Unlike other harvestmen, members of this family of so-called daddy longlegs do not usually have very long legs. Like other harvestmen, they can be quickly distinguished from spiders by their one-part, egg-shaped body (not easily separated into head and abdomen), and by their not spinning webs. They also lack venom glands.

There is only one genus, with two similar species, commonly encountered in Missouri:

  • Libitioides albolineata: usually darker brown than L. sayi, with a whitish V-shape, lines, or other markings. Widespread in the eastern United States.
  • Libitioides sayi: light caramel color, lacking white markings. A Great Plains species.
Other Common Names
Armoured Harvestmen
Cosmetid Harvestmen
Size

Length (not including appendages): about ¼ inch.

Where To Find

Statewide.

Usually found under rocks or logs or in the leaf litter of wooded areas.

Unlike other groups of harvestmen, which are usually scavengers, armored harvestmen are predators, capturing and eating small insects and other animals they can subdue.

Armored harvestmen and their daddy longlegs relatives progress from egg, to juvenile, to sexually mature adult. Unlike other arachnids, males of the various harvestmen groups fertilize females directly, via an intromittent organ, as opposed to transferring a sperm packet (spermatophore) to the female.

The family name, Cosmetidae, is the family-suffix form of the type genus, Cosmetus, which comes from a Greek root word that means "well-ordered," "ornate," or "adorned." Armored harvestmen in genus Cosmetus live in Central and South America and many of those species are ornately marked. The same Greek root gave us the words cosmetic and cosmos.

There are more than 700 species in the armored harvestmen family Cosmetidae; the family occurs natively only in the New World. In the United States, there are 4 genera, comprising 6 species. The rest of the hundreds of species in this family overwhelmingly occur in Mexico and southward to northern South America.

Media Gallery
Photo of an armored harvestman walking on the ground
Members of the armored harvestman suborder typically have rather short legs and live on the ground under rocks, logs, and leaf litter. They are predators.
David Bruns
Use of this image is restricted to MDC only
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Photo of an armored harvestman walking on the ground
Similar Species
About Land Invertebrates in Missouri
Invertebrates are animals without backbones, including earthworms, slugs, snails, and arthropods. Arthropods—invertebrates with “jointed legs” — are a group of invertebrates that includes crayfish, shrimp, millipedes, centipedes, mites, spiders, and insects. There may be as many as 10 million species of insects alive on earth today, and they probably constitute more than 90 percent all animal species.
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