The mistake of shipping weed to India along with a consignment of wheat from the US during the 1950s inadvertently gifted India a beautiful species of butterfly.
The simple but elegantly attractive Bath White butterfly, which derives its name from the English town of Bath where it was first recorded in Britain, is now found in the trans-Himalayan range.
Uttarakhand-based lepidopterist Peter Smetacek, who is considered an authority on Indian butterflies and moths, has presented the case of migration of this species in his book 'Butterflies on the Roof of the World'.
"Once, I was standing on the lawn talking with a visitor when a female butterfly laid its eggs on a weed a few metres away. This was too good an opportunity to miss, so I gathered the plant and eventually bred the caterpillars that emerged," Smetacek writes in the book published by Aleph.
As he tried to unravel the mystery behind the relationship of the butterfly larva and the plant on which it fed, he found that the plant was Virginia Peppergrass or Lepidium virginicum. The butterfly, therefore, came to be known as Bath White.
"This weed had been brought to India by mistake as part of wheat shipped from the United States during the 1950s and had spread rapidly through the country," says the naturalist, who has already described a dozen species of butterflies and moths new to science. The book is a result of spending a lifetime chasing butterflies in meadows and forests.
The butterfly was first recorded in Nainital district?s Bhimtal town on April 21, 1961 and thereafter became a resident.
"The only record I could find was that Virginia Peppergrass had reached Netarhat Plateau in Chhota Nagpur, Bihar. This would mean that the butterfly could theoretically extend its distribution eastwards through Nepal," writes Smetacek who also runs the Butterfly Research Centre in Bhimtal.
On checking information available on butterflies in Nepal, he discovered that the species was reported throughout that country in a book published in 2006, although it was not mentioned in a list published in 1951.
"As soon as the food plant spread through the Himalayas during the second half of the twentieth century, the butterfly followed and today is found along the southern face of the range from Kashmir eastwards at least as far as the eastern border of Nepal," says the book.
The butterfly's distribution is restricted to the trans-Himalayan zone of West Himalayas not by either temperature or humidity, but by the availability, or, rather, non-availability of a suitable larval food plant, it concludes.