- Lifespan
- 2–6 weeks as an adult butterfly; multiple generations per year mean individuals live only a few weeks each
- Size & Weight
- wingspan 26–32 mm; 0.3–0.5 g
- Habitat
- Gardens, hedgerows, parks, and woodlands where holly and ivy plants are abundant, from lowlands to upland areas.
- UK Distribution
- Found throughout England, Wales, and southern Scotland; resident with two to three broods per year, numbers supplemented by continental migrants in autumn.
- Diet
- Adults feed on nectar from a variety of flowers including marjoram, bramble, and bugle; caterpillars feed exclusively on holly and ivy leaves.
- Predators
- Robins, wrens, spiders, and parasitoid wasps (particularly Listroderus nyrifrons, which parasitises caterpillars).
- Mating Season
- March to October, with peak activity in spring and autumn
- Breeding
- Two to three broods per year; females lay single eggs on host plants; caterpillars take 10–14 days to develop; chrysalis stage lasts 7–10 days in summer, but overwinters as chrysalis on ivy.
- Behaviour
- Holly Blues are highly territorial and males patrol vigorously in warm, sunny weather. They have a characteristically erratic, fluttering flight. Adults are attracted to damp ground and often visit puddles to drink.