Ah, the devious little parasite from AD&D. Used them many times when the adventuring party was getting sloppy in one of my dungeons.
Back when I was in high school, a throat leech was a person who acted all nice and proper to get a girl out on a date but then got all handsy and started kissing their victim's neck, many times leaving hickeys and other red blotches so the throat leech's fellow parasites would see the conquest the next day at school. Eventually some of the leeches developed a reputation and some girls avoided them, but then again they were seen as "bad boys", which attracted the girls who liked that kind of dude or were rebelling against their parents.
I knew several of these creatures, and some were so good at what they did that they had a series of girls who would get spotted necks, got upset and wore a turtleneck, then listened as the throat leeches sweet-talked them into another date (and more hickeys). Many of the girls were quite smart besides this repeating pattern. I guess they got what they wanted by the third or fifth session. I had some of these girls as friends but I wouldn't listen to their bitching about the guys who would do this since all it would do is make them upset and defend their abuser. I learned early on that this was a type of Kobayashi Maru that was impossible to win.