Dorsal longitudinal muscles

Definition

A paired set of internal muscles running lengthwise along the dorsal (upper) side of the insect thorax or abdomen, originating on anterior tergites and inserting on more posterior tergites; the principal depressors of the wings in the indirect flight mechanism of many winged insects, and important in body flexion and posture control in all segments.

Etymology

Latin dorsum (back) + longitudo (length); descriptive of position and fiber orientation along the body axis

Example

In a blow fly (Calliphoridae), the dorsal longitudinal muscles contract to pull the notum downward, levering the wings upward via the pleural wing process; their antagonistic action with the dorsoventral muscles generates the rapid oscillation of asynchronous flight.

Synonyms

• DLM
• dorsal longitudinals

Related Terms

• dorsoventral muscles
• Indirect flight muscles
• Asynchronous muscle
• Tergum
• notum
• myofibril
• thoracic musculature
• wing depressor

Usage Notes

In the strict sense, refers to the segmental muscles of the terga; in flight physiology, often denotes specifically the power muscles of the mesothorax and metathorax. Contrast with ventral longitudinal muscles (sternal) and with extrinsic direct wing muscles that attach to the wing base. The term is sometimes used more broadly for any dorsally positioned longitudinal musculature in arthropods, including arachnid opisthosomal muscles, but the flight-related sense dominates in entomological literature.