The Asian longhorned beetle is a recent immigrant to North America, which has established populations in areas around New York City and Toronto. As of 2007, Asian longhorned beetles in Chicago Illinois are believed to have been eradicated.
The larvae of the Asian longhorned beetles tunnel in tree trunks feeding on the wood. A variety of hardwood trees are attacked in North America, especially maples.
Several sites on the internet have done a good job of providing fact sheets for the Asian longhorned beetle. Please visit the links below for more information.
USDA Forest Service Pest Alert:
http://www.na.fs.fed.us/spfo/pubs/pest_al/alb/alb04.htm
Additional USDA Forest Service information, including identification, tree species attacked, and quarantines:
http://www.na.fs.fed.us/fhp/alb
USDA links, including Factsheet, questions & answers, photos, and recent infestations:
http://www.aphis.usda.gov/newsroom/hot_issues/alb/alb_general_info.shtml
Woody ornamentals site from the Department of Entomology, Cornell University:
http://www.entomology.cornell.edu/Extension/Woodys/EPP_ALB.html
Asian longhorned beetle (LEFT) vs. Whitespotted sawyer (RIGHT)

Photographs by E.R. Hoebeke, Cornell University.
Asian longhorned beetles (ON LEFT) may be confused with another large beetle, the Whitespotted sawyer (ON RIGHT), which is native to North America. The Whitespotted sawyer feeds on conifer trees that are dying, stressed, or recently cut down (rather than maples or other hardwoods).
Asian longhorned beetles are 3/4 inch to 1 3/8 inch long (20-35 mm), glossy black with white spots, and very smooth.
The Whitespotted sawyer is also about an inch long, but somewhat smaller (15-28 mm), and is bronzy-black, covered with fine dimples instead of being smooth.
The elytra (E in photos) of Asian longhorned beetles have up to 20 irregularly distinct white spots. In contrast, the elytra of Whitespotted sawyer females are mottled with whitish patches, and the males are generally completely bronzy-black.
The scutellum (S in photo) of the Asian longhorned beetle is generally black; unlike the Whitespotted sawyer scutellum, which is generally white (covered with white or ashy-colored scales).