Seem to be a lot of dogs around these parts. Might be interested in this study*:

Prospective medical evaluation of 7 dogs presented with fly biting

The data indicate that fly biting may be caused by an underlying medical disorder, GI disease being the most common. The authors suggest that the term “fly biting” be replaced by “neck extension” syndrome.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500118/#b16-cvj_12_1279

* Caveat: very tiny, preliminary study, presented because it suggests a less severe, more approachable diagnosis.