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tarsus, tarsi, tarsomere, tarsal formula

Insect Leg Legs of hymenoptera Anatomy of a Spider Spider Anatomy for glossary
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
No Taxon (Glossary)
No Taxon (T)
No Taxon tarsus, tarsi, tarsomere, tarsal formula
Explanation of Names
From Greek, tarsos, sole of the foot (1).
tarsus noun, plural tarsi, adjective tarsal - the "foot" or last part of the insect leg, attached to the end of the tibia. It typically has five joints, or segments, called tarsomeres. (Sometimes the number is reduced, and this can be a useful identification aid, e.g., in many beetles.) The tip of the last segment often has tarsal claws, and sometimes there is a pad of hairs underneath these, called a pulvillus (plural pulvilli).
See diagram of insect and spider legs above.

Photos illustrating tarsi:

Tarsal formula refers to the number of tarsomeres on the front, mid and hind legs e.g. "Scarab" Beetles have a tarsal formula of 5-5-5 or 5 tarsomeres on the front legs, 5 on the middle ...
This character is especially useful at family rank and higher.
Print References
Gordh, A Dictionary of Entomology, p. 908 (1)
Internet References
Wikipedia: Arthropod leg
Works Cited
1.A Dictionary of Entomology
George Gordh, David H. Headrick. 2003. CABI Publishing.