Seq # 185020010

Dialectica imperialella (Zeller, 1847) Species

Last modified: Sept. 6, 2023, 5:28 p.m.

A rare species in Belgium, at first only known from a publication in 1860 from NA. The second observation was done in 2008 in AN. Since then, the species is recorded from other provinces, but always in very small numbers, except in some rare occasions. But it is still underrecorded, because the species seems not to be rare in the Netherlands.


Family: Gracillariidae > Subfamily: Acrocercopinae > Genus: Dialectica > Species: Dialectica imperialella
Vernacular names
Smeerwortelsteltmot (NL), Fen slender (EN), Silberfleck-Beinwellfalter (DE)
First mention in Belgium
De Fré Ch. 1860. Lépidoptères nouvellement découverts en Belgique. — Annales de la Société entomologique belge 4: 113–115. On page 109. view page




The imago has a dark brown ground colour with pure white markings. It sits with its front part upturned at an angle of 45°.

Museum specimens

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Specimens in nature

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The first instars are light green, but later on the larva becomes rosy to brownish red.

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The mine starts as a small, spiral on the underside of the leaf but turns into a blotch mine which most of the times includes the initial spiral. The last instars also eat the palissade tissue so that the mine becomes visible from the upperside of the leaf in the form of some brownish dots.
See also, and


A flat, reddish cocoon.

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Like most of the species in the subfamily Acrocercopinae, the full-grown larva exits the mine, drops to the ground and pupates there between leaf litter. It first spins a flat, reddish cocoon. In some rare cases, the caterpillar constructs its cocoon on the leaf without descending to the leaf litter.

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Flight periods

One generation per year: May and June.

Observed on

Host plant (species):
Symphytum officinale, Pulmonaria officinalis and Lithospermum officinale

The larva mines in the leaves of Lithospernum officinale, Pulmonaria officinalis and Symphytum officinale.

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