Grey Dagger (Acronicta psi (Linnaeus, 1758))
Scientific name: Acronicta psi (Linnaeus, 1758)
Common name: Grey Dagger
Other names: Other scientific name: Triaena psi.
French name: Psi
Order: Lepidoptera
Suborder: Heterocera
Family: Noctuidae
Subfamily: Acronictinae
Wingspan: 30-45 mm.
Biotope: Mainly woodland areas, parks and gardens.
Geographic area: Western Europe, from southern Spain to Finland.
Flight time: Mid-may to September.
Number of generations : 2, 1 in the northern part of its range.
Caterpillar: Greyish with a broad white longitudinal stripe on each side and a broad yellow dorsal stripe. This yellow stripe is bordered with greyish blue stripes showing red marks circled with black. There is a tall black hump near the head.
Host plant: Many trees and shrubs like Birches (Betula spp.), Oaks (Quercus spp.), Elms (Ulmus spp.), Hawthorn (Crataegus monogyna) and Blackthorn (Prunus spinosa).
The Grey Dagger's forewings are a pale grey colour with dagger-shaped black markings. Its English common name come from these markings. Some moths are a darker grey colour.
The hind wings are greying brown with dark veining.
It is almost impossible to tell alone dark forms of the Grey Dagger from the Dark Dagger (Acronicta tridens) by a simple visual look. Their caterpillars differ.
The caterpillar pupates in a cocoon under tree bark or in rotten wood.
The Grey Dagger over winters as a pupa.

Grey Dagger (Acronicta psi) - Yvelines, France - May 27th 2008
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Grey Dagger (Acronicta psi)
The colour pattern of the Grey Dagger's wings provides an efficient camouflage when landed on tree trunks.


Grey Dagger (Acronicta psi) - Yvelines, France - May 27th 2008
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Grey Dagger (Acronicta psi)
You can clearly see the dagger-shaped (or the Greek Psi letter) marks on the wings.
The pale grey colour allows to differentiate this moth from the Dark Dagger (Acronicta tridens).


Grey Dagger (Acronicta psi) - Yvelines, France - June 5th 2011
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Grey Dagger (Acronicta psi)
It is very easy to tell apart caterpillars of the Grey Dagger species.
I have found this one in my garden on one Prunus cistella.


Grey Dagger (Acronicta psi) - Yvelines, France - August 5th 2016
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Grey Dagger (Acronicta psi)
After observing the caterpillar in my garden, I had to observe the imago there.


Grey Dagger (Acronicta psi) - Yvelines, France - September 27th 2020
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Grey Dagger (Acronicta psi)
I took the liberty of temporarily moving this caterpillar to take a picture of it with a uniform background.

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