Arenose: a surface that is sandy or gritty.
Areola: a small cell on the wings of certain Hemiptera: see also areae Hymenoptera; the central of three median areas on the metanotum: = 2d median area; upper median area.
Areolate: with small defined areas, like a network.
Areole: Lepidoptera; see accessory cell, cell and cellule.
Areolet: one of the small spaces between veins of net-veined insects.
Argentate: shining, silvery white.
Argenteous: silvery.
Argillaceous: of the texture, appearance or color of clay.
Arid: Applied to regions in which the normal rainfall is insufficient to produce ordinary farm crops without irrigation, and in which desert conditions prevail: see humid.
Arid transition area: comprises the western part of the Dakotas, northern Montana east of the Rockies, southern Assiniboia, small areas in southern Manitoba and Alberta, the higher parts of the Great Basin and the plateau region generally, the eastern base of Cascade Sierras and local areas in Oregon and California.