The reports on larvae are somewhat divergent, depending on the species and the condition of the larvae (fresh versus alcohol-preserved): The fully-grown caterpillar of Niphopyralis myrmecophila (according to material preserved in alcohol) is approximately 14 mm in length, 4.4 mm thick at its largest diameter, and completely colourless, with the spiracles visible as fine, shiny colourless dots.

The larval body is naked, hardly flattened, markedly tapered anteriorly and posteriorly, with all segments bulging out almost in a physogastric way.

The two epicranial halves are almost triangular and encompass a large tongue-shaped frontal plate that reaches posteriad to the occipital opening.

Each side of the head bears six ocelli, with the upper five in a curved line, and the sixth separate more ventral; the latter ocellus is not pigmented like the others.

The well-developed anal prolegs have an angularly curved frontal row of 11 crochets in falf-grown larvae and more in older ones.

Furthermore, they lack a proboscis, have reduced palpi, and the males exhibit bipectinate antennae, a mix of characters that for a long time hindered their correct placement among Lepidoptera (see Systematics).

[4] The caterpillar of Niphopyralis myrmecophila lives in a flat oval self-spun casing consisting of two slightly curved halves that fit precisely onto one another.

They actively participate in the maintenance of the ant nest by repairing and reinforcing walls with spinning thread.

After settling down, the moth usually walks a short distance, with its wings held horizontally and skewed backwards.

In resting position, the wings are normally held vertically, covering the body from the sides, and the abdomen is raised to approximately 45°.

[6]: x  Twenty-three years later, in 1916, Walter Karl Johann Roepke described Wurthia and erected the new subfamily Wurthiinae, which he placed in Arctiidae (now Arctiinae).

Common (1990), realising that Wurthia is misplaced in Schoenobiinae, re-established the subfamily Wurthiinae with this genus as the sole member.