Chandigarh, Aug 18 - 'I've watched you now a full half-hour/ self-poised upon that yellow flower/ and, little butterfly! indeed/ I know not if you sleep or feed....'

These words from a poem by William Wordsworth come to one's mind as one walk down the Madhya Marg and Panjab University (PU) campus in Chandigarh and behold hundreds of butterflies fluttering in the sky.

Over 70 species of butterflies are found in Chandigarh. The smallest butterfly, Freyeria Putli, with a wing size of 16 mm to 18 mm, is also found here and can be seen flying very slowly near thick grass.

According to Varinder Walia, a professor in the department of Zoology at Panjab University, this is a seasonal phenomenon.

'As per the normal reproduction cycle of butterflies, this is the most conducive time of the year for them to lay eggs. New leaves come out and they always prefer to lay their eggs on these fresh and delicate leaves,' Walia told IANS.

Walia, who has also written a book on butterflies, 'Butterflies of North-West India', added: 'There are certain host trees in some areas of the region. Butterflies keep on flying from one tree to another, presenting spectacular scenery for the onlookers.'

'On seeing these hordes of butterflies in the sky, many people claim that they are migrating uphill as there is a strong possibility of an earthquake in the plains. This is absolute rubbish as the butterflies are just shifting from one host tree to another in search of fresh leaves,' Walia said.

Explaining the huge number, Walia said: 'If there are 100 butterflies and if each of them lays 250 eggs, then in a span of a few days there would be around 25,000 butterflies.