Dispersal of the Pine Needle Scale, Phenacaspis pinifoliae (Fitch), (Diaspididae: Homoptera)

Abstract

The dispersal of the pine needle scale has long been a problem to entomologists. Although its transfer on nursery stock has been accepted as a means of dispersal, the method of its spread from tree to tree in a localized area has not been investigated previously. There are two stages in its development when it is able to move about by its own volition: the crawler or first instar nymphs wander for short distances on the twigs of the host tree and the adult males move about freely. Effective spread of this scale occurs only in the crawler stage. Phoresy is unlikely because nymphs have extreme difficulty in crossing small gaps such as would be encountered in transferring from a needle to an insect or bird and parent scales do not secrete substances attractive to carriers as described by Mahdihassan (1933) for some lac-insects. Because of the limited motility of the first instar nymphs, dissemination by wind required investigation.