The literature on Harmandiola helena is inconsistent. Felt's original description places the opening on the upper side, while Gagne 1989's drawing (though only listed as "possible helena") shows the opening on the lower side. Russo suggests that his Harmandia sp. A, which seems to match our p-tremuloides-like-populnea and does open on the upper side, might be related to H helena, suggesting the name may belong to that morphotype. Our current interpretation follows Gagne. An additional complication is that in iNaturalist observations, galls closely resembling Gagne's drawing are largely observed on Populus grandidentata, a host not listed in any existing literature. It is added tentatively as a host based on those unconfirmed observations (eg) or (eg).

Regardless of its correct name, the gall pictured in this entry closely matches the description of the European species Harmandiola pustulans on Populus tremula.

The gall pictured in this entry can be distinguished from other midge gall morphotypes on Populus leaves by the following traits:

• Larva concealed within galled tissue
• Gall evenly protruding from both sides
• Opening in linear slits on the lower side of the leaf

- Gallformers Contributors: (2023) Gallformers ID Notes^©