Head to head
Common Blue vs Large Blue
Common Blue
VS Large Blue
The common blue and large blue are two European blue butterflies that both depend on ants, one with a mild partnership and the other with an extraordinary parasitic relationship.
| Common Blue | Large Blue | |
|---|---|---|
| Scientific name | Polyommatus icarus | Phengaris arion |
| Habitat | Flower-rich grassland, dunes, and waste ground | Flowery grassland with thyme or marjoram and the right species of red ant |
| Caterpillar food | Bird's-foot trefoil and other legumes | Wild thyme or marjoram flowers at first, then ant grubs |
| Ant relationship | Ants guard the caterpillars from predators and parasites in return for their sweet secretions | The caterpillar's scent tricks red ants into carrying it into their nest, where it feeds on their grubs |
| Range | Europe, North Africa, and temperate Asia | Flowery grassland from western Europe to central Asia, now rare in many countries |
| British history | Not specifically documented | Died out in Britain in 1979 and was reintroduced from Sweden in the 1980s |
| Population | Widespread and common, though it has declined where flower-rich grassland has been lost | Declined across much of its range and survives in scattered colonies kept going by conservation management |
| Conservation status | Least Concern, with a stable population | Endangered, with a decreasing population |
Common Blue vs Large Blue: common questions
Which blue butterfly eats ant grubs?
The large blue, whose caterpillar is carried into a red-ant nest and feeds on the ants' grubs.
Was the large blue extinct in Britain?
Yes, it died out in Britain in 1979 and was reintroduced from Sweden in the 1980s.
Which blue is more at risk?
The large blue, which is Endangered, while the common blue is Least Concern.