Wahlgreniella Hille Ris Lambers
This is a genus name for a collection of very poorly understood aphids that occur across much of North America, Europe, and Asia. I have been pursuing Wahlgreniella for many years, hoping to accumulate enough material to determine how many species there are in western North America and to understand their life cycles. Unfortunately, I have found enough aberrant samples on unusual host plants that the work is far from done. One example: in September of 2014 I was collecting in the mountains of the Lincoln National Forest (New Mexico), and was walking through the mountain-top solar observatory site called Sunspot (about 2800 meters elevation), through a windy blowing fog. On the highest parts of the mountain grows a rose, with strange morphology, that I have never seen elsewhere and on it was a Wahlgreniella that looked different from anything I have seen before. Another example I have been pursuing since my graduate school years: a common species that I have documented to have a monoecious life cycle on Paxistima myrsinites (Celastraceae) in the mountains of northern California, Oregon, and Washington. The final link in these efforts was finding the fundatrix in the central Cascades of Oregon on 30 May 2018.
Wahlgreniella nervata (Gillette)
This species is most known for its presence on roses across much of the world. As Blackman and Eastop note, it is thought to be heteroecious in western North America between Rosa and various Ericaceae. I have always been skeptical of this, but have failed to document anything different. I definitely see it overwintering on roses, both wild and cultivated, and I definitely see it colonizing Arbutus and Arctostaphylos later in the spring and summer. Further, despite much effort I have never seen evidence of fundatrix or sexuales on either of those genera. Since moving to southern Oregon, I am surrounded by this aphid in the nearby forests, and have almost become convinced that this heteroecy is in fact true in the field.
Wahlgreniella apterous vivipara from rose in our garden in Idaho.