India, Jan. 26 -- If you know what to look for, you can almost time the surge of illegal Bangladeshi immigrants into India. Typically, it coincides with heavy rain and dense fog, which make the illegal border crossings easier. It's a migration fuelled by desperation caused by the lack of jobs in Bangladesh. The numbers recently swelled due to the political instability in India's eastern neighbour.

Sometimes the desperation has personal roots too. A 26-year-old woman arrested by the Pydhonie police from a brothel in Grant Road two weeks ago had made the arduous journey across the border because she had nothing left in her homeland. She was from Dhaka, she told the police, and moved to Mumbai illegally after the death of her husband.

"I d...