SWARMING BUGS ATTACK SCREENS!

It's not your imagination, 90210 and Melrose Place fans-Fox is defacing your favorite shows by superimposing a transparent network logo in the lower-right- hand corner of your TV screen for approximately one minute before and after commercials. ''It helps viewers to identify Fox in an increasingly competitive channel environment,'' network spokesman Jeff DeRome explains. Fox is the first broadcast network to layer its logo over prime-time entertainment programs, but the practice is common among such cable networks as C-SPAN (the first network to do it, in 1979), CNN, CNBC, VH-1, and Comedy Central. Known as ''bugs'' (because insects land on TV screens) or ''boogers'' (''They land on TVs too,'' says Marc Chusid, Comedy Central's vice president of on-air promotion), the pesky logos also pop up on the CBS Evening News, NBC Nightly News, and will soon adorn ABC news and sports shows and Good Morning America. A Current Affair and Hard Copy also mark their footage, although that didn't stop Copy from pirating Affair's racy home video of Amy Fisher last year and blowing up the images to eliminate its rival's logo. Affair threatened to sue, but Copy apologized. Few viewers have complained about the logos. ''I think people are ignoring them, which means we have to come up with the next generation,'' says Chu-sid. ''Maybe a guy in the corner of the screen yelling, 'Hey, you! You're watching Comedy Central!''' Sounds like a job for Joey Buttafuoco.