Accessory subcostal vein: the vein given off from the subcosta and branching toward the apex of the wing in Perlidae.
Aceous or aceus: suffix; similar to, or of the nature of.
Acephalous: without a head.
Acerata: arthropods without true antennae Arachnids and Limulus
Acetabular caps: Hemiptera; the coxal cavity.
Acetabuliform: like a shallow saucer with more or less incurved sides.
Acetabulum: the cavity into which an appendage is articulated; specifically the coxal cavity, - q.v.; also applied to a cup-like cavity in the sucking mouth of maggots.
Achreioptera: ordinal term proposed for the coleopterous family Platypsyllidae.
Achromatic: free from color; tissue that does not stain readily.
Acicular: needle-shaped; with a long, slender point.