Spanish moon moth

Actias (=Graellsia) isabellae

1. Identification

• Common name: Spanish moon moth
• Scientific name: Actias isabellae Graells
• Synonym: Graellsia isabellae Graells
• Order: Lepidoptera
• Family: Saturniidae
• Conservation status: protected species of high ecological value; it is not considered a pest.

2. Description of the species

• Adults: large moths, with translucent pale-green wings and brownish-pink patterns; long, elegant hind tails; wingspan between 60–100 mm.
• Males: highly developed feathery antennae; generally smaller than females.
• Females: larger and more robust; less feathery antennae.
• Larvae: green, with bluish tubercles and dark rings; they reach a large size before pupation.
• Pupae: formed in silky cocoons among pine needles or in the leaf litter.

3. Main hosts

• Mountain pines, especially: Pinus sylvestris and Pinus nigra
• It occurs mainly in mountainous areas and natural coniferous forests.

4. Symptoms and damage

(Species not considered a pest; damage generally negligible)

• Larval feeding on pine needles, normally without significant impact.
• Slight, localised defoliation may occur, but without negative economic or ecological relevance.
• The presence of the species is, in fact, an indicator of good environmental quality.

5. Biological cycle

• One generation per year.
• Adults emerge between April and June, depending on the altitude.
• Eggs laid on the needles of the host pines.
• Larvae develop during the summer, passing through several instars.
• Pupation in late summer or early autumn, in a silky cocoon.
• Overwintering as a pupa, with adults emerging the following spring.

6. Monitoring

(Applied mainly for conservation, not for control)

• Observation of adults during the flight period.
• Searching for cocoons on branches and in the leaf litter.
• Monitoring of populations in protected areas and mountain forests.
• Light traps may be used only for scientific purposes, never for control.

7. Management measures

(Focused on the conservation of the species)

• Preservation of natural Scots pine and black pine forests.
• Avoiding intensive felling, removal of the leaf litter and practices that destroy cocoons.
• Minimising the use of insecticides in areas where it occurs.
• Maintaining habitat continuity and ecological corridors.
• Conservation and captive-breeding programmes in some regions.

Bibliographic references

• EPPO Global Database – Actias isabellae.
• CABI Invasive Species Compendium – Actias isabellae.
• Vila, R. et al. (2018). Butterflies of Europe and the Mediterranean Basin.
• Tremewan, W. G. et al. (1995). Biology and ecology of Graellsia isabellae.
• Gómez‑Bustillo, M. R. et al. (1982). Lepidoptera of the Iberian Peninsula.