Seth Belson remembers getting a phone call last month asking him to remove a bee swarm the size of a Volkswagen from a man's front yard in Merchantville, New Jersey.

The beekeeper found a mass of bees towering 50 feet (15 meters) above the ground. There was nothing he could do but wait for them to move on, he said.

''It was mind-blowing,'' Belson said. ''It sounds like a train when 50,000 bees take off within seconds of each other.''

Swarms of wild honeybees have increased in the U.S. mid-Atlantic region this year, according to Belson. That's a hopeful sign for commercial beekeepers across the country who have seen their hives devastated in recent years by parasitic mites and a phenomenon termed colony collapse disorder.

Nationally, the commercial honeybee population dropped more than 36 percent last winter, according to a survey released in May by the Apiary Inspectors of America. Commercial bees, which do most of the pollinating for one-third of U.S. crops, have declined over the past two decades to about 2.3 million honey-producing colonies from about 3.5 million.

Belson says he has removed about 40 swarms at elementary schools, golf courses and houses this year, compared with one call to do so the past two years.

'Premature to Say'

''Hopefully it's a sign that bees are coming back, but it's very premature to say that,'' said Belson, who is president of the South Jersey Beekeepers Association. ''If this happens over the next two years, we'll call it a trend. At this point, it's just a hopeful aberration.''

A resurgence of feral honeybees is important because beekeepers build their farms in part by collecting from the wild. It may also suggest that some bees are building immunity to the varroa mite, a common killer of colonies, said Tim Schuler, New Jersey's chief beekeeper.

Schuler attributes the new swarms this season to mild weather and abundant rain. Commercial bees add $15 billion annually in value to U.S. crops, according to the Agriculture Department.

Gary Neil, a beekeeper in Williamstown, New Jersey, said he too has been removing swarms. ''We're doing a lot more than we did last year,'' he said.

There are more of the clusters in Virginia as well, said Alan Fiala, former president of the Virginia State Beekeepers' Association, who lives in Falls Church. Glenn Davis, a board member in Bates City, Missouri, for the Midwest Beekeepers Association, said he's gotten more calls to remove swarms as well.

Congressional Hearing

The rebound may not have reached California, the nation's biggest beekeeping state. Steve Arnold, who specializes in bee removal around California's San Luis Obispo County, said he hasn't seen any signs of resurgence in wild bees. Swarms typically thrive in mild climates, and the weather has been erratic in the region this year, Arnold said.

Little progress has been made in understanding the cause of colony collapse disorder, or CCD, because of the small number of people studying it relative to the size of the issue, researchers and bee experts told the U.S. Congress today at a House Subcommittee on Horticulture and Organic Agriculture hearing.

''While in the long run honeybees will most likely survive, our beekeepers may not,'' Maryann Frazier, an apiculturist at Pennsylvania State University, told the committee. ''Direct financial assistance is overdue, and is critical to their survival, or next year's agricultural pollination needs will not be met.''

Pesticides, Mites, Viruses

Pesticides, mites and viruses are the leading suspects behind the sudden, massive disappearance of bees that occurred in 35 states and three continents last year and began in the U.S. as early as 2004.

Wild bees have a tougher time surviving than commercial bees, which are closely monitored by beekeepers, Frazier said in an interview June 20. Their resilience may be a sign that some bees are adapting to the diseases and parasites out there, New Jersey's Schuler said.

''There seem to be some blood lines that are more resistant to the mites than others,'' Schuler said.

The resurgence this season may be short-lived, Frazier said.

''We have years like this where we have increases in swarming,'' she said. ''It's pretty much a temporary phenomenon.''