The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum ( dorsal), the mesosternum ( ventral), and the mesopleuron ( lateral) on each side. The mesothorax is the segment that bears the forewings in all winged insects, though sometimes these may be reduced or modified, as in beetles (

Coleoptera Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

) or Dermaptera, in which they are sclerotized to form the elytra ("wing covers"), and the Strepsiptera, in which they are reduced to form

haltere ''Halteres'' (; singular ''halter'' or ''haltere'') (from grc, ἁλτῆρες, weights held in the hands to give an impetus in leaping) are a pair of small club-shaped organs on the body of two orders of flying insects that provide infor ...

s that attach to the mesonotum. All adult insects possess legs on the mesothorax. In some groups of insects, the mesonotum is hypertrophied, such as in

Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

Hymenoptera Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...

, and

Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

), in which the anterior portion of the mesonotum (called the mesoscutum, or simply "scutum") forms most of the dorsal surface of the thorax. In these orders, there is also typically a small sclerite attached to the mesonotum that covers the wing base, called the tegula. In one group of insects, the

Hemiptera Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...

, the dorsal surface of the thorax is typically formed primarily of the prothorax, but also in part by the enlarged posterior portion of the mesonotum, called the scutellum; in the

, the scutellum may or may not be visible, usually as a small triangular plate between the elytral bases, thus similar in position to the

n scutellum. In

and

the mesothoracic scutellum is also distinct, but much smaller than the mesoscutum.

References

Insect anatomy {{insect-anatomy-stub

See also

References