"Made for a school project, short backstory to the critters:

Depression floats around the body, its sharp scales and pointed needles slice and poke at the beings around it, and intoxicate them, making them feel unwanted and disgusted at themselves, separating them from the rest of their species. This way they can feast on the loner via their two suckers, draining their will to be.

Loneliness, on the other hand, will fly around, excreting noxious gas on the creatures around it. The creature will feel alienated, and avoid contact with others. Loneliness then can brush up against them, and attach its heavy strands of hair, which are actually eggsacs, ensuring their safety because the loner will want to avoid others."