squeemish(?) tail,licking off fur

Question
My about 7 year old spayed fem.short hair cat is licking off the fur on her lower tummy and now inner legs. She does this thing where she will be sitting there and all of the sudden she acts like something is freaking her out and  she has the creapy crawlies and her tail is like an alien or something crawling under her skin.. She will sometimes chase her tail in cirles .You almost see her "ripple" the fur on her back. She is an indoor cat(always has been).This  started about a a couple weeks to a month ago whereas the fur licking just started. I have not seen any fleas and have checked her tail to see if there was something there but there wasn't.We live in the country,so she gets an occ. mouse here and there. I tried to worm her the other day but she threw it up.Her "sister" seems to be doing all right (all 25  fat and lazy lbs of her)oye!Any suggestions or ideas would help.Thank you in advance.(Also i have not made a change in their food,and she weighs about 7 or 8 lbs.)

Answer
Her skin is readcting to something and she itches.  That can be from many things, but allergic skin disease would be high on my list.  Thebest thing to do is to have your vet give a shot of DepoMedrol, which is a long acting, safe steroid to take away the itching.