THEY bribe border guards or carry false documents. They come on tourist visas and don't leave. They trek on foot through Kruger Park, past man-eating lions and leopards.
The intrepid immigrants are Africans - from Zambia, Angola, Mozambique, and Zimbabwe - drawn by the better job prospects and higher paychecks in neighboring South Africa.
The demise of South Africa's white-ruled government with last April's multiparty elections improved relations with black African states - and encouraged thousands of destitute from nearby countries to seek jobs in the region's economic powerhouse.
This provoked a crackdown by the new African National Congress-dominated coalition government that faces a dilemma - how to protect jobs for its own impoverished black constituency while not alienating neighbors who harbored its guerrillas during the long underground struggle against white rule.
A new xenophobia has sprung up, with mainly black trade unions and workers hostile toward their new competition. And the new government, which wants to deliver jobs and housing for its own people before local elections in October, is under pressure to better police borders.
Instruments of apartheid once used against ANC guerrillas - random ID checks, raids on suspected ``safe houses,'' 24-hour military patrols along the borders - are now employed against the new immigrants.
``There is a growing tide of xenophobia among South Africans who believe their situation will improve if all illegal aliens are deported,'' said a recent survey by political scientist Hennie Kotze. It showed that more than half of ANC supporters believed illegals worsened their problems, and most other political parties strongly opposed the presence of the new migrants.
One of the newcomers is Samuel Zuane, who on Christmas Eve became another statistic in South Africa's campaign against illegal aliens.
The Mozambican gardener who had slipped back and forth across the border since 1991 was finally caught by South African police while walking without identification papers through the grimy streets of downtown Johannesburg.
Sitting under police guard in John Vorster prison, he admitted that once deported back to Mozambique he would try to return to his Eldorado - South Africa. ``There is no work back in Maputo,'' he said. ``There is only hunger and misery.''
The cells of John Vorster prison, notorious in the 1980s for holding political prisoners, are increasingly filled with illegal aliens. For many like Mr. Zuane, the risks are worth it: He earned $16 a month in Maputo as a factory worker compared to $160 a month as a gardener in Johannesburg.
Experts believe perhaps 2 million aliens are now in South Africa. Over the past two months, an estimated 60,000 were deported - compared with 96,600 in all of 1993 and 53,418 in 1990, the year apartheid began to be dismantled. Nearly all are Mozambicans - dispelling hopes that 1992 peace accords there would herald an exodus back home.
At some northern borders, as many as 1,000 may cross every month - a 100 percent increase over last year - despite razor wire and foot, horse, and motorcycle patrols by police, and soldiers backed by helicopters.
``The traffic has definitely increased since South Africa's elections. Many people were scared before of the South African police and afraid to stay here,'' says Desmond Lackey, the officer in charge of the main border crossing with Lesotho, where migrant remittances account for up to 45 percent of the country's gross national product.
Mr. Lackey said many Lesotho citizens had family across the border in South Africa. With similar languages they often remained undetected after their three-month tourist visas expired.
Most illegal migrants eventually make their way to Johannesburg, the country's commercial center. They mill about the arrivals hall at the main rail station, where employers gather in search of cheap restaurant and domestic help.
The women slip into the obscurity of suburban kitchens, working well below menial wages. Millions of Lesotho and Mozambican men have traditionally toiled undetected in the deep gold mines.
Some aliens congregate in squatter camps or tenements, resorting to prostitution, street vending, or drug peddling if all else fails.
South Africa's new government is divided over what measures to take. It has sought advice on increasing border security from United States experts well-versed in Mexican immigration.
The hard-line Home Affairs Minister, Zulu Chief Mangosuthu Buthelezi, wants to see stiff fines and prison terms for employers giving jobs to aliens.
But ANC ministers, many of whom had sought refuge in neighboring countries during apartheid, call for more delicacy in keeping back the tide.
Defense Minister Joe Modise said a fence along the border with Mozambique in Kruger Park should be extended - but that its deadly electrical voltage should remain cut off.
Deputy Foreign Minister Aziz Pahad said South Africa must remember its new role as regional leader and not grow isolationist. ``We must have a humane policy,'' he said, arguing against mass deportations. ``You can not respond by simply throwing people out of the country. The consequences would lead to destabilization in the region.''