The Grey Dagger and Dark Dagger moths

Grey Dagger (Acronicta psi) by M. Virtala

The Dark Dagger and Grey Dagger

The Grey Dagger (Acronicta psi) and Dark Dagger (A. tridens) are two British moths that look almost identical as adults but very different as caterpillars. Both moths have curious black dagger markings on their fore-wings, hence their name.

The Grey and Dark Dagger moths are also found throughout Europe, the Near East and many parts of Asia. They are in the Noctuidae, a very large family of moths that are also known as "Noctuids", "Owlets" and "Millers." Many species look very similar and there is often confusion in identifying them.

Strangely the Dark Dagger is often the paler in colour than the Grey Dagger. But the real natural mystery is why the two moths look so alike and yet their larvae are so different?

The Grey Dagger

The Grey Dagger is thought to be the commoner of the two species but this is not certain due to the confusion with identification of the adult insects. The only way of determining which moth is which is by examination of the genitalia by an expert on moths.

The Grey Dagger's fore-wings are a pale to a blackish grey and the dagger-like markings are also thought to resemble the Greek letterpsi ψ and this is how it was given its scientific species name. The hind-wings are a dirty grey but generally not as pale and as white as those of the male of the Dark Dagger. The wingspan is 34-45 mm. The adult moth feeds on nectar.

The Grey Dagger flies in June and overwinters in the pupa stage in a fairly flimsy cocoon that is spun under loose bark. The caterpillars usually feed on Hawthorn but also can eat, Blackthorn, Plum, Pear, Apple, Sallow and Birch. It has also been reported feeding on Pyracantha and is often found in gardens with fruit trees and ornamental shrubs.

It is a pretty creature with a bright yellow line down its back, black-edged red spots along each side and a raised hump on ring four of its body. It is far more colourful than the rather dowdy adult moth although the adult's black dagger markings add to its charm.

Grey Dagger caterpillar in Public Domain

The Dark Dagger

The Dark Dagger moth is found in England and Wales, and though present in Scotland and Ireland is thought to be not at all common in either. It is also distributed throughout Europe from Fennoscandia to the Balkans and down into Italy and Turkey. The species is found as well in Russia and as far over as China, Korea and into Japan.

Dark Dagger by M. Virtala

The Dark Dagger flies in June and July, and in captivity a second brood in October is sometimes produced. The caterpillar of the Dark Dagger feeds from August to October and is found on Hawthorn, Blackthorn, Rowan, Buckthorn, Plum, Pear, Apple, Birch and Sallow.

It does not have such a high hump as the related Grey Dagger's caterpillar, nor does it have a bold yellow line down its back. The larva of the Dark Dagger is black with a broad reddish stripe along it back in the middle and one other on each side. The middle stripe is interrupted with white and has a small black hump on the fourth ring and another broader one on the eleventh. The caterpillar, like that of the Grey Dagger has numerous hairs sprouting from its body as well.

Dark Dagger caterpillar by Lilly M

Like the Grey Dagger it overwinters as a pupa in a silken cocoon that it spins under loose bark. It is reported that it can sometimes spend two winters in this stage.

The Dagger Moths are well worth looking out for although you are more likely to see the colourful caterpillars.

Copyright © 2012 Steve Andrews. All Rights Reserved.