Petiole (insect anatomy) a pedicel, but in entomology, that term is more correctly reserved for the second segment of the antenna; while in arachnology, 'pedicel' is the accepted term to define the constriction between the cephalothorax and abdomen of spiders. The plump portion of the abdomen posterior to the petiole (and postpetiole in the Myrmicinae) is called the gaster. The structure of the petiole is an easy way to visually classify ants, because the major subfamilies of Formicidae have structural differences: some ants have two-segmented petioles, while others have a single-segmented petiole. Petiole may also be used in the context of wing veins,
Insect flight stability in its amplitude. To simplify the calculations, one must assume that the lifting force is at a finite constant value while the wings are moving down and that it is zero while the wings are moving up. During the time interval Δ"t" of the upward wingbeat, the insect drops a distance "h" under the influence of gravity. The upward stroke then restores the insect to its original position. Typically, it may be required that the vertical position of the insect change by no more than 0.1 mm (i.e., h=0.1 mm). The maximum allowable time for free fall is then