Holly Blue

Scientific Name - Celastrina argiolus

Flight Period - March to October (two broods)

Overwinters as - Pupa

Habitat - Hedgerows, gardens, parks, woodlands

Larval foodplants - This butterfly uses a lot of food plants but common ones include Holly, Ivy, Dogwood, Buckthorn etc.

Conservation status - Low priority

Northamptonshire distribution - Widespread

Best public sites to see them - Anywhere with suitable habitat. They can be abundant in urban parklands such as Abington Park in Northampton

The Holly Blue is a familiar sight in our gardens and parks and in some years they can be very abundant. Their populations do fluctuate significantly year on year and this is primarily due to their parasite, the parasitic wasp Listrodromus nycthemerus, whose sole host is the Holly Blue. You can see the changing fortunes in the annual Holly Blue abundance figures in the chart below.

However, when the Holly Blue has a good year they can be easily studied, due to their habit of frequenting gardens and parks. They have an incredibly long list of larval foodplants, and more plants get added to it each year, but by planting a few examples such as Dogwood, Holly and Ivy, they can be quite easily attracted into the garden where egg-laying and larvae can be easily observed. However, finding their pupae in the wild is very hard to do as they are exceptionally well hidden. They can sometimes be confused with the Common Blue but the Holly Blue is far more likely to be the blue butterfly flying around the bushes in the garden. The underside is a very distinctive pale blue with dark spots and is unmistakable when seen well. For more information about how to identify the commoner Blues please click here.

Holly Blue Distribution 2018 - 2022

Female Holly Blue

Male Holly Blue

Female Holly Blue egg laying on Dogwood showing the underwing pattern

Holly Blue egg

Holly Blue larva

Holly Blue pupa