Filiform

Filiform antennae are threadlike, with uniformly sized segments.
Filiform antennae are threadlike, with uniformly sized segments. Modified from A Manual for the Study of Insects, John Henry Comstock, 1895 (Public Domain)

Definition:

Filiform is a term used to describe certain insect antennae. The term comes from the Latin filum, meaning thread. Filiform antennae are slender and thread-like in form. Because the segments are of uniform widths, there is no taper to filiform antennae.

Filiform is a common morphological form of antennae found in many insect groups. Examples of insects with filiform antennae include:

Filiform is just one of many morphological forms of insect antennae. See also:

Source: Borror and DeLong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson