In the state's battle against mosquitoes, a familiar maxim of war applies: The enemy of my enemy is my friend.

After enlisting small fish such as Gambusia affinis to gobble up the bloodsucking insect's larvae, the New Jersey Department of Environmental Protection now has another ally: Macrocyclops albidus, a tiny shrimplike crustacean native to New Jersey.

It has been distributed to mosquito-control authorities in Gloucester, Atlantic, Cumberland, Monmouth, Warren, and Bergen counties.

"This is another environmentally friendly tool that can be used to battle mosquitoes without having to resort to pesticides," said Bob Kent, administrator of the DEP's Office of Mosquito Control Coordination.

The crustacean, which is a copepod, has a voracious appetite for mosquito larvae, state entomologists said. It has been used to battle mosquitoes wherever they breed, from roadside ditches to clogged downspouts.

"It's especially effective in smaller containers or pools of water and is really good in dealing with the Asian tiger mosquito, which can breed in the tiniest of places - even a bottle cap," Kent said.

The crustacean has been used in warmer locales from New Orleans to Vietnam and was approved this spring by state scientists for a full-fledged rollout in New Jersey after field trials that began in 2006.

The critters are being mass-cultivated in West Trenton at the Department of Agriculture's Phillip Alampi Beneficial Insect Rearing Laboratory.

"These creatures all make excellent mosquito deterrents and can be more effective than pesticides, which require multiple applications every mosquito season," said Claudia O'Malley, technical adviser in the Office of Mosquito Control Coordination.

"In some places, these creatures can eliminate or greatly reduce the need for any applications at all," she said. "That is good for the environment, but bad for mosquitoes."