The term Scarab has come to mean any older style Viper before the Starhound, and as such, represents many styles and policy of fighter craft.

The actual Scarab itself was the forerunner of the Starhound Viper, and is in all aspects just a less able version of the current Viper. It is similar in appearance (with more angled wings) and contains the same equipment and engines as the Viper, just less modern (and thus able) versions.
A recon version was never built.

Scarabs are still found in many parts of the known Universe, being used by pirates and rogues, or by civilian defence forces around the edge of Colonial space.
[Another model of the Scarab can be seen in the episode "The Long Patrol" being flown by an Enforcer.]