About Pemphigus spyrothecae Passerini, 1860
Pemphigus spyrothecae Passerini, 1860 individuals are green, red, or yellow in color, and have a smooth outer texture. The species develops its outer surface as the edges of the petiole of Populus nigra thicken, flatten, and twist. A gall forms in parallel to the petiole's shape, taking on a spiral structure that matches the inside of a snail's shell. The fundatrix — a parthenogenetic female aphid that grows from an overwintering fertilized egg on the primary host plant — is pale green. Fundatrices allow second-generation alatae to develop inside the gall. Galls typically mature between late August and early September, changing color from green to red as they mature. Once mature, alatae leave the gall through many small pores located along the seams of the gall's spirals. This species is geographically distributed across Europe, Tunisia in North Africa, western Siberia, Pakistan, and certain locations in Canada.
