BIOL 312 Lecture Notes - Lecture 6: Insect Wing, Insect Flight, Plecoptera
14 Nov 2017
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Wings: veined wings on 2nd and 3rd thoracic segments. Flaplike cuticular projections supported by cross- veins (tracheae, blood, nerves). Connected to thorax by articular sclerites; thorax is a rigid box. Direct vs. indirect flight muscles (most use indirect, odonates use direct). Indirect f. m. indirected connected to wings because thorax is tight rigid box. Muscle action deforms rigid thoracic box and wings move predominant flight muscle adaptations: click mechanism: wings only stable in up or down position, asynchronous muscles: many contraction cycles per impulse. Carboniferous (~320 million years ago had already diversified into at least 10 orders). Wings evolved from thoracic lobes (not articulated, tracheation evolved later), evolved from appendages (e. g. limbs or gills) (articulated or tracheaeted) All primitively wingless hexapods are terrestrial, all the basal winged groups have aquatic juveniles (dragon-, damsel-, mayfly). It is not clear if aquatic lifestyle is derived in these groups or if it evolved independently. Squirrels dropping insects from heights to break them.
