Spanish fly

Lytta vesicatoria

1. Identification

• Common name: Spanish fly, blister beetle
• Scientific name: Lytta vesicatoria L.
• Order: Coleoptera
• Family: Meloidae

2. Pest description

• Adults: Elongated, metallic, bright‑green body; 10–20 mm in length; filiform antennae; wings and elytra with characteristic sheen.
• Larvae: Complex development with several stages (hypermetamorphosis); mobile early larvae (triungulins), followed by sedentary stages in the soil.
• Eggs: Laid in the soil, in masses.

3. Main hosts

• Lindens.
• Ash trees.
• Other ornamental and spontaneous broadleaf trees.
• The larvae are predators of grasshopper eggs and other orthopterans.

4. Symptoms and damage

• Partial defoliation due to the feeding of adults on the leaves.
• Damage generally localised, but can be significant in young or ornamental trees.
• Presence of adults easily visible due to the metallic coloration.
• Risk of contact with cantharidin, a vesicant substance present in the body of the adults.

5. Biological cycle

• Adults emerge in late spring and early summer.
• They feed on leaves of host trees before mating.
• Females lay eggs in the soil.
• Larvae prey on orthopteran eggs and pass through several larval stages.
• Winter spent in larval stages in the soil.
• One generation per year.

6. Monitoring

• Direct observation of the tree canopy during spring and summer.
• Visual identification of adults due to the metallic‑green coloration.
• Assessment of the level of defoliation in ornamental or young trees.

7. Management measures

• Cultural: Regular monitoring of sensitive trees; manual removal of adults when possible; avoid direct contact due to cantharidin.
• Biological: Maintenance of balanced ecosystems that support natural predators of orthopterans (reducing the availability of eggs for the larvae).
• Integrated protection: Intervention only when defoliation justifies it; avoid unnecessary treatments, given the ecological role of the larvae as predators of orthopteran eggs.

Bibliographic references

• Bologna, M. A., & Pinto, J. D. (2002). The Meloidae (Coleoptera) of the world.
• EPPO Global Database – Lytta vesicatoria.
• CABI Invasive Species Compendium – Lytta vesicatoria.
• Turco, F. et al. (2003). Biology and ecology of blister beetles (Meloidae).