Males can get confused with very pruinose examples of Keeled Skimmer (O. coerulescens), particularly in further south in Europe when O. coerulescens can develop a pruinose thorax.
I’ve tried to summarize some of the main differentiators on a comparison diagram.
- yellow/pale brown pterostigmas
- “Rspl subtends double row of cells (variable in number)” – Dijkstra/Lewington
- ♂ develops almost entirely blue pruinose body
- ♂ very pale blue/white frons
- ♀ abdomen is pale brown with thin dorsal line flanked by a pair of dark spots in each segment