Although the paper cited below does not treat or mention Chironomidae, some of its results and conclusions may be interesting to those of us wishing to dig for deeper understanding. In any case, it is always worth considering whether morphological differences one observes are so relevant to biological function and/or evolution that they justify a corresponding separation of taxa.
Herath, B., Dochtermann, N. A., Johnson, J. I., Leonard, Z., Bowsher, J. H. (2015) Selection on bristle length has the ability to drive the evolution of male abdominal appendages in the sepsid fly Themira biloba. J . Evol. Biol. 28(12): 2308-2317.