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Message: <blockquote data-quote="Gavia_immer" data-source="post: 1505419" data-attributes="member: 65934">Chapter 3: The other Polyommatus: Chapman's BlueI have already presented the first of the Polyommatus Blues, the Common Blue. I am going to continue with the rest of this group, as all are pretty similar and very confusing.Chapman's Blue (Polyommatus thersites) is said to be the Butterfly more similar to Common Blue. In fact I cannot separate them only by the upperside. It is about the same size (smallish-medium) with a violet hue and white edges. But the underside helps a lot. It has not the additional cell spot, which is the best ID tip.There is another ID tip that works very well in specimens found in Spain, not no well in other parts of Europe though. The orange dots of the underwing tend to be triangular in Chapman's Blue, both male and female, whereas they are more rounded in Common.You can see these features in pic a, Chapman's Blue. The second pic is a Common Blue, in comparison.Besides, if the specimens are in good condition, they can be IDed by the texture of the ground colour on the underwing. Chapman's Blue is very smooth and velvety, whereas Common has a rather rough feel to it. My pics are not good enough to appreciate well this feature. Perhaps somebody can provide better ones.</blockquote>