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Iwakuni Marine Corps Air Station and local Japanese officials are discussing final details this week of a project to construct a barrier inside the installation’s perimeter fencing to keep black widow spiders confined to the base.

Black widow spiders first were discovered on base in 1997, when three were found near a hangar. More were noticed in 1999; by November of 2000, an all-out war began to eradicate the poisonous spiders.

Since 2000, base pest control personnel have systematically exterminated black widow spiders found in dark, out-of-the-way, cramped spaces, such as under street drainage grids, in pipes, on piles of scrap materials and around storage buildings. This month, they have found and killed 13,824 of the creepy arachnids, base officials said Wednesday.

No one from the Marine base has been bitten, on base or off. Nor have the spiders been found outside the base boundaries.

Nonetheless, a spokesman for the Hiroshima Defense Facilities Administration Bureau said, the decision to build the 3,062-yard, $862,790 barrier is firm. “The fence will be placed there in order to prevent the spiders from spreading,” he said.

Iwakuni city, DFAB and base officials met Tuesday and Wednesday to review the details, said Capt. Stewart Upton, base spokesman. The Japanese government is funding the project through DFAB and city civil engineers are to install the structure, he explained.

“We are making every possible effort, not to just control, but to totally eradicate the spiders,” Upton explained. “In the meantime, if the barrier provides some assurance to local residents, so much the better.”

The approximately 20-inch tall barrier, made of polycarbonate panels inside the existing security fencing, will not encircle the entire base. It’s being installed from the fencing starting at the same side of the Monson River as the main gate, continuing to the Northside gate. Pipe-like traps with chemicals to kill the spiders will be placed along the barrier, about 6 inches above the ground.

The barrier’s installation will begin in mid-May and be completed by March 15 next year the DFAB spokesman said.

Upton said a special inspection is planned a few days before the May 5 Friendship Day events to ensure no spiders are found in high-traffic areas.

He said inspections are held regularly, based on a priority system:

• Priority 1: areas where spiders have been found in the past.

• Priority 2: family housing and boundary fencing.

• Priority 3: areas immediately surrounding Priority 1 areas.

• Priority 4: spot inspections elsewhere.

Yokosuka Naval Base entomologist Akira Masui determined in 2001 that the spiders were Southwestern black widows, which display the most common traits of all black widow spiders, including red hourglass shapes on the underbellies and a length of about 1½ inches, including the legs. Black widow spiders of this type are not native to Japan, according to entomologists.

The females are poisonous, while males and juveniles are harmless. Normally passive, they deliver their poisonous bites when disturbed.

Less than 1 percent of all black widow bites are fatal, with small children and the elderly the most vulnerable to serious reactions or death from bites, medical officials have said; most adults who are bitten recover completely in two to five days.

Base officials said they remain unsure how the creatures first spun their way to the base. Investigators have theorized the desert arachnids hitched rides on commercial trucks bringing building supplies from the U.S. southwest.

Iwakuni’s Navy Branch Medical Clinic keeps a more-than-adequate supply of spider anti-venom on hand, as do local hospitals, base officials said.

— Hana Kusumoto contributed to this report.


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