Firstly, I am absolutely no expert on this. I am only going by things I have beenj told. Basically, as an adoptive, when we (my wife and I) encountered this custom we had to research it out. It is my understanding that beings of the Sivaloka would not be attracted. Only lower astral forces would be, and again, not 'dangerous' or bad, just more instinctive ones. I have been taught the opposite is true. Devas of higher vibration are attracted to incense, flowers, and the like. People who live a poor lifestyle such as promiscuity or alcoholism are also more likely to be affected by 'lower' astral forces. That is why we clean up for puja, temple etc.
Blood itself a 'lower' force. We don't find people using blood for abhishekam. My analogy to sharks and bears was an attempt to explain it, but it seems that didn't work. Perhaps the idea of fermones and sexual attraction would be a better analogy as it is more subtle. I remember teaching teenagers and watching the boys 'hover' around the girls, subconsciously, and not even aware that they were doing it, or why. It was quite subtle. This whole area of 'other beings' etc. is quite subtle. Have you ever stepped around the corner of a building,and just had the feeling that something was there? Maybe that will help.
Aum Namasivaya
Thankyou for the reply, Eastern Mind.
One example why i mentioned the veerashaivas or lingayaths was that they consider themselves to be pure shaivites. They wear the linga on their body, and its not restricted to men alone. I do not know if women remove the linga from their person during menstruation (the ladies i know do not). To them, the physical body is just a being.
Their concept as i understand seems to revolve around this: When there is union of the atma with the formless divine, and if the omnipresent divine is with us always, to protect us; and
if god is there for his devotee no matter what the physical condition of his devotee is, then there is no need to segregate women during menstruation.
Am not sure why blood is considered a 'lower' force. Bengali women too, i hear, offer prayers to Kali irrespective of whether they are having periods or not. i certainly do not think women become unacceptable creatures to God during those 5 days.
Sometimes things just seem like cultural beliefs ingrained in us since young, and after a certain age or stage, it may not be easy to give it up or outgrow it (happens to be so in my case, am not really comfortable with offering prayers during menstruation, though i understand God loves us no matter what, and its no big deal really).
Some yoga schools consider both devas and asuras as our own instincts, with all the worlds being within us. To have a clutter-free mind, some people are asked to light incence, offer flowers to God, to keep their mind calm and clear before starting on the meditation practice. Over time, they outgrow this, as their mind gets rather 'freed up' of clutter and baggage with time. And they start off by offering prayers to God in their mind (manasa puja). And yes, generally i notice that such people do seem to have strong instincts and premonitions.
Have not come across info from those dealing in spirits, like mediums, as well as those doing past life regressions, that there are 'beings' attracted to blood from the astral plane (perhaps the astral place is considered a 'higher' plane maybe).
Pretas, i hear, are considered unsatisfied souls. Like say victims of murder or homicide. So they are sorta vengeful, and try to cause harm to seek revenge from those who had caused them harm. Did not come across info that they are 'attracted' to blood so far (will try to gather more info on this).
Blood happens or happened to be viewed as a 'vital force', as a positive energy, in quite a few cultures, including sections of hindusim in the past:
http://www.tamilbrahmins.com/general-discussions/2187-drinking-okay-4.html#post22203
Regards.