Alder beetle (Agelastica alni)

The Alder leaf beetle is a 7-8 mm long dark metallic blue leaf beetle that feeds on alder (Alnus) and is occasionally found on other deciduous trees such as beech (Fagus sylvatica), hazel (Corylus) and hornbeam (Carpinus betulus). Also known as the alder flea beetle. Here are some key points about this particular beetle:

1. Appearance: The alder leaf beetle is a small, shiny beetle with a metallic blue-black or blue-green colouration. It typically measures around 4 to 6 millimetres in length.

2. Habitat: As the name suggests, these beetles are associated with alder trees. They can be found in alder forests and areas where alder trees grow.

3. Lifecycle: Alder leaf beetles undergo complete metamorphosis, including egg, larval, pupal, and adult stages. The larvae are known for their distinctive slug-like appearance and feed on alder leaves. It overwinters as adults, which emerge in the spring, sometimes in large numbers.

4. Feeding Habits: Both the larvae and adult beetles feed on the leaves of alder trees. While alder leaf beetles are generally not considered highly destructive, in some cases, large populations can cause defoliation, especially if the trees are stressed or weakened by other factors.

5. Distribution: Alder leaf beetles are found in various parts of Europe and Asia. They are more commonly encountered in regions where alder trees are prevalent.

Seen in Osterly Park in August 2020