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While having the opportunity to observe a PE closely, as it took up moisture from the damp surface of a ride, I noticed that the tip of the proboscis was often turned so that the upper surface was in contact with the ground.
I also photographed the partially-coiled proboscis, which appear to show some roughening near the tip or, possibly, a sensor pad.
Can anyone enlighten me - are there sensors on the tip of the proboscis and is this the normal way of routing moisture into the groove that can be seen along the upperside of the proboscis?

Mike

What marvellous pictures, Mike!

It is certainly normal to press the upperside of the proboscis onto the ground - often to stab the slightly curled upper surface repeatedly into the substrate. I have no idea what sensors might be there but wonder whether your picture might not show minute grains of very fine sand stuck to the end - the ground does look as if it has grains of that size in it.

Guy

Hi Mike,
Guy is correct. These are silt grade particles adhering to the proboscis. It is common for Emperors to retire to nearby shrubs and trees after prolonged 'puddling'/'salting', in order to clean particles from the proboscis by repeatedly wiping the organ across the surface of a leaf. This action has probably been responsible for the possibly incorrect belief that the species spends a lot of time feeding on honeydew, for which there is limited evidence.
Neil

Thank you Guy and Neil. My photo of the coiled proboscis was a crop from an overall shot of the butterfly, so was unfortunately not sharp enough to resolve the sand grains. Now Neil has explained, it seems fairly clear that this is what the photo shows

Sussex Kipper wrote:This action has probably been responsible for the possibly incorrect belief that the species spends a lot of time feeding on honeydew, for which there is limited evidence.

An interesting comment, though presumably this species (together with Purple Hairstreak) does take up some sugars in this way?

Mike

Hi Mike,
It's debatable how much of this actually goes on (in Purple Emperor). I suspect they get most of the sugars they need from sap runs, which are a huge draw for them - male and female. The image below shows an Emperor cleaning his proboscis on a low oak after a long period on the deck, although it would be very easy to mistakenly attribute this to the intake of honeydew. The lower image is of a female at a sap run.
Neil

Thanks again, Neil. Yes I have certainly seen PE feeding at a sap run and on a few occasions, whole clusters of Red Admirals.

Mike

That's interesting. Although the foresters have made a complete mess of my local emperor woods this year, cutting down most of the sallow (and elm, aspen and alder buckthorn, adding insult to injury), I have noticed that females in particular gravitate towards the cut logs and since there is a huge pile of these at the moment there is some hope that at the end of the season I might find one or two looking for goodies on them. This female, who I never got really close to, was particularly interested in cut branches near a log pile last year. I didn't think of sap but I guess that was what was drawing her:


(August 1st, 2011)

Guy

Well, that's the first time I've heard of female Emperors being attracted to liquid forms of sustenance.

Strange how tales of people using fecal matter as bait are folklore when it appears all we need do is find our own naturally occuring sap runs!!

here's an old photo, which I took in Whitecross GreenWood, Oxon, of a PE apparently feeding on sap. Not sure if this one was male or female.
Mike