Quadraspidiotus perniciosus, the San Jose Scale, can be considered harmful to humans because it kills plants and trees. They can be found many places throughout the United States and tend to feed on trees that produce fruit. While females spend their entire lives attached to trees, the male form may have wings which he uses to fly around to find mates. During the reproductive cycle of this species, females can produce several thousand scales in one season causing large infestations. They eat the limbs, fruit and leaves of trees by sucking the sap. Infestations can cause limbs to die, deformations and poor color in fruit, reduced yields and it can even kill the tree that is hosting.