Measuring body size in flies/insects > "Mesothorax length (the distance from the tip of the scutellum to the most anterior part of the mesothorax)" From Bergland et al 2008. Would that be this distance (green line)? !enter image description here If not, how would you describe that distance?

I think you are correct, but I'm not an expert in Diptera/Drosophila morphology. Since the prothorax (pronotum) and metathorax are greatly reduced in flies, you mostly see the mesonotum in dorsal view, and this includes the scutellum. Personally, I think it would have been more accurate of them to label this structure **mesonotum** , or at least _dorsal mesothorax length_ , since _mesothorax_ could just as well imply a ventral view (mesosternum).

More information can be found at this webpage: _Flies - Morphology and anatomy: Thorax_, which state that:

> The mesonotum occupies most of dorsal view of the thorax. In order anteroposterior we can identify four parts, called as follow (McAlpine, 1981): prescutum, scutum, scutellum, and postnotum. The scutum is the most large, condition considered apomorphic for the entire order of Diptera.

Also see this picture of the mesonotum from diptera.net

!enter image description here