If you go back, take your camera but if you forget and carry a cellphone that has a camera, use that 
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Sometimes a photo is helpful, especially if you can find out its original habitat. A photo may help to see an eyespot that was not obvious on observation (if it does this reduces the field a lot). Even photoing just the eyes can help to see a star pattern (aculeatus has one but I see one on hummelincki too). A picture may also show the outer rings on the suckers. Hummelincki and aculeatus usually show blue/purple, vulgaris almost black and bimac an orange. The underside of hummelincki and aculeatus is often a speckled peach but you need to remember that these creatures can alter their color and usually is not always
Unfortunately, asking these ID questions will likely get you nowhere even from the collector
.Sometimes a photo is helpful, especially if you can find out its original habitat. A photo may help to see an eyespot that was not obvious on observation (if it does this reduces the field a lot). Even photoing just the eyes can help to see a star pattern (aculeatus has one but I see one on hummelincki too). A picture may also show the outer rings on the suckers. Hummelincki and aculeatus usually show blue/purple, vulgaris almost black and bimac an orange. The underside of hummelincki and aculeatus is often a speckled peach but you need to remember that these creatures can alter their color and usually is not always
Unfortunately, asking these ID questions will likely get you nowhere even from the collector
This is 
