NAIROBI, March 30 -- DURING this rainy season, swarms can be seen leaving the thousands of anthills in and around Gilgil, a quiet agricultural town in Kenyas Rift Valley that has emerged as the centre of a booming illegal trade.

The mating ritual sees winged males leave the nest to impregnate queens, who also take flight at this time. This makes it the perfect time to chase down queen ants to sell on to smugglers who are at the heart of a growing global black market, that taps into the pet craze for keeping ants in transparent enclosures designed to observe the insects as they busily build a colony.

It is the giant African harvester ant queens, which are large and coloured red, that are most prized by international ant collectors –...