These variations of the Hunter have purple patches to their skin. They're more deadly than the regular Hunter, they're stronger, quicker, and can administer a dose of poison from its venomous claws.
Treat these Sweepers the same way you'd treat a normal Hunter, except try harder to not let it touch you, as being poisoned can really hinder your progress.
[1] Exact number can depend on certain game conditions.
Location
Chemical Storage Room - Military Training Facility B1
1 Sweeper - Appears here when you are playing as Chris. Bursts through the metal grating immediately after acquiring the Clement Σ from the refrigerator, but only if you have already obtained the Door Knob.
Jet Hangar Corridor - Military Training Facility B1
1 Sweeper - Appears here when you are playing as Chris, only if Spotters appear in this room, and only if they are the ones that appear after acquiring all three proofs from the Airport but before acquiring the Eagle Plate. The Sweeper will appear if one of these Spotters detects you.