Pemphigus spyrothecae is an aphid that causes galls to form in the leaf petioles of its host trees. The galls are seen more often than the aphid.  The galled petioles have 2-3 twists, which loosen up later in the year to release aphids through a slit along the gall.

The rare Pemphigus protospirae has gall with more than 3 twists, and only slight thickening of the petiole. It has not been recorded in VC55

Gall Adult

Anywhere that poplar trees are present.

Galls from June to late autumn.

It is an aphid that lives in colonies and soldier aphids tend to be located near to the opening of the gall to defend it from predators.

Widespread and thought to be fairly frequent in England.

Status in Leicestershire and Rutland not known.

https://influentialpoints.com/Gallery/Pemphigus_spyrothecae_Poplar_spiral_gall_aphid.htm