I love the question!

I too have often wondered if there was a connection to what I have felt inside to what some people call a Psi Vampire, a vampire that feeds off the energy of others. To a lot of people, this probably makes absolutely no sense, to others, it makes a lot of sense.
Psi Vampires can get their energy from various means. Sometimes it is through intimate contact with their mate, sometimes it is just being around other people, and some claim they can get energy by asteral projections, meaning they just think about someone and get energy that way. I am familiar with the intimate contact method. I have yet to admit that I am a Psi Vampire, but I fit the mold if such a thing exists and I have physical proof. There is something to it.
What Ann talks about in an earlier post above, feeling drained after an encounter with her bf after sex, might be because he is a Psi Vampire. When I have sex with my mate, I feel energized, but she feels weak and tired, and I cannot explain it either (of course I am constantly kissing and softly biting her neck all over! She's not too crazy about my intense neck fetish.).
Why just yesterday I felt the need (a craving) to just cuddle and neck, no sex, and I felt that I really needed to be close to her. I needed physical contact. I can not explain the feeling other than a real need to be with her. Some people may call that a hunger. After an hour of cuddling, which she enjoyed too, I felt completely recharged, but she felt weak and drained. Did I need her energy? Did I feed on her energy? I needed something, and felt better afterwards, that part is true. After an hour or so, she felt better too and wanted to cuddle again. Her energy had returned. BTW, she doesn't believe in vampires one bit and the only thing my necking does to her neck is tickle a lot. But she can't explain why she feels so drained after we come together either. And if I am not a Psi Vampire (which I'm not sure of either), I don't know why I feel so much better, not weaker, but recharged after coming together with her. If anyone has a better word for it, I would like to hear it.
Scientists claim two people living together will outlive a person who lives alone. There is something that happens to us when we share our lives with another person, or even a pet, but especially if we share our lives with another person. There is something going on here, that I cannot put words to. For example, how do you feel when you and your lover hug? Kiss? Neck? Do you feel warmth come over you? Do you feel good? Some people are extremely sensitive to these feelings. I am very sensitive.
Regarding spiders, the only thing I can say is they are true blood sucking vampires from the insect world. The way they feed is very interesting. First they spin their webs, then when their prey fall victim to their spun web, they rush over and inject them with something that paralyzes them and turns their insides into a soup. Then they drink their meal until all that is left is the victims shell. I am amazed by these insects because they are so different. Some people have called spiders the wolves of the insect world.
Mosquitoes, are another insect blood sucker, or should I say the female mosquito, but she only feeds on blood to fertalize her eggs. Her saliva contains properties that prevent blood clotting, so she can drink and drink her blood until her belly is full. That mosquito bite that itches that's left behind is the reaction left from the mosquitoes saliva.
Did this help?