Holly blue vs Spring azure

These two are easy to mix up. Here's how to tell a holly blue from a spring azure, and whether either one bites or stings.

≠The key differences

Holly blue is a very similar Eurasian relative that does not occur in North America; a small blue in eastern North America is not this species.

	Holly blue	Spring azure
To humans	Non-toxic	Non-toxic
Size	26-34 mm wingspan	22-35 mm wingspan
Colours	Pale sky blue, Darker blue/steel, Pale grey underside, Black (wing margins and spots)	Pale blue, White, Gray-brown
Family	Lycaenidae	Lycaenidae
Habitat	Gardens, hedgerows, woodland edges, parks and scrubby open areas.	Open woodlands, forest edges, scrub, gardens and hedgerows where host shrubs and early flowers occur
Range	Widespread across Europe, parts of North Africa and temperate Asia.	Eastern and central North America: from southern Canada through the eastern United States (populations and exact boundaries vary with taxonomy)
Active	Two main flight periods in many regions: spring (April-May) and summer (June-August); flies during daylight hours.	Early spring into early summer; in many areas one main spring brood with occasional later broods
Pest?	No	No

Small blue butterfly with 26-34 mm wingspan.
Male upperside pale sky blue with narrow dark edge; female has broader black margin and darker scaling.
Underside pale grey/whitish with small neat black spots; wings held closed at rest showing underside.
Spring individuals often associated with holly; look for eggs or larvae on holly flower buds.

Small size with a wingspan around 22-35 mm; much smaller than most white or sulphur butterflies
Upperside pale blue (males) with narrow dark margins; underside pale gray to off-white with faint small spots
Flight is low, quick and fluttering in early spring near host shrubs and woodland edges

Holly blue is a very similar Eurasian relative that does not occur in North America; a small blue in eastern North America is not this species.

Holly blue: Non-toxic. Spring azure: Non-toxic. Holly blue butterflies are harmless to people. Harmless to people.

Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.