An experienced bog spider will only strike when the lady is on her way out of the toilet, thus avoiding an uncomfortable situation when a lady is on her way in to attend to business.
The Bog spider reasons that this is where he will find the highest concentration of ladies and the lowest concentration of any competition. It is purely a numbers game for these astute bog spiders.
Bog Spiders are also known to get it on with particularly ugly girls because
a) they can get away with it as the chances of being seen by your mates is slim. Only other bog spiders may notice and won't break the code.
b)let's be honest - the girls who respond to the bog spider's tactics are not normally the cream of the crop.
When you are good mates with a known bog spider, you may be able to refer to him as Boggy.
The toilets at Shepards Bush Walkabout are a Bog Spiders paradise.