Taiwan is to close one lane of a major highway to protect more than a million butterflies, which cross the road on their seasonal migration.

The purple milkweed butterfly, which winters in the south of the island, passes over some 600m of motorway to reach its breeding ground in the north.

Many of the 11,500 butterflies that attempt the journey each hour do not reach safety, experts say.

Protective nets and ultra-violet lights will also be used to aid the insects.

Taiwanese officials conceded that the decision to close one lane of the road would cause some traffic congestion, but said it was a price worth paying.

"Human beings need to coexist with the other species, even if they are tiny butterflies," Lee Thay-ming, of the National Freeway Bureau, told the AFP news agency.

Under the bridge

Each year thousands of butterflies die when turbulence generated by fast-moving cars drags them into the traffic or under the wheels of oncoming vehicles.

Ecologists hope the triple-action effort of lane closure, protective nets and ultra-violet lighting will dramatically increase the milkweed's chances of reaching the breeding ground.

The protective nets are designed to force the butterflies to fly higher, reducing the chances of them getting caught in the traffic.

Ultra-violet lighting will be used below an elevated section of road to encourage the butterflies to head beneath.

The measures are estimated to have cost $30,000 (£15,200).