With spring comes the mosquitoes as the days warm. One way to tell if they are out is the bushy hairs at the top of the tail. This is often mistaken for sweet itch or worms. It is usually caused by mosquitoes. As a horse moves he lifts his tail and the mosguitoes converge on the delicate skin on the underside which makes him itchy. He will rub against something trying to get relief. Thus the bushy tail hairs. The mosquitoes may also go after the thinner hairs at the top of the tail. An inexpensive, effective remedy is to slather petroleum jelly on the underside of the tail and around the anus and vagina, even some in the bushy hair. With a mare, also slather it underneath around her teats as itchy teats will get her tail rubbing. The black flies, if you have them, or gnats, feast under there.