Phytobia

Phytobia is a genus of flies in the family Agromyzidae, with a worldwide distribution principally in Europe and the Americas.

==Description== All known larvae of Phytobia feed on the young xylem within stems of woody plants, creating concealed galleries that may reach considerable lengths (reportedly up to 17 m in P. betulae). P. betulae lays its eggs on the bark of new-growth twigs of suitable birch trees and, after hatching, larvae tunnel downwards along the shoot within the differentiating xylem layer, sometimes reaching the base of the tree. Adults are small- to medium-sized flies (approximately 5 mm in the case of P. betulae). Confirmed host plant families for Phytobia species include Betulaceae, Fagaceae, Rosaceae, Salicaceae, Sapindaceae, and Cupressaceae in North America, Europe, and Australia, with Asteraceae also hypothesized to be a host family based on the finding of possible larval sign on the shrub Wedelia calycina in Guadeloupe. Larval tunnels mar the appearance of certain woods used commercially, and thus may be of economic importance.