Sunday, 16 April 2017

Emperor assembling question

Hello again.  Following my last post, on assembling male Emperor moths, I have been pondering the way that my three, after finding their way to the captive female from possibly long distances, made a mess of their final approach and ended up fluttering about in our shed while their target was perched unconcerned on the outside wall.

My theory, after reading about the males making sometimes erratic circles as they get near to the female (rather than heading straight towards her) is that one of these manoeuvres took them through the open door of the shed (a couple of inches to the right of her perch) and thus into what turned out to be a trap, working on the same lines as a lobster pot or indeed Robinson moth trap, in that the door and windows acted like funnels, easier to enter by rather than exit through.

Does this make sense?  I also got the feeling that a captive female simply left in the open (where she showed no desire to escape or fly away) was much more effective than confinement in a muslin bag. Does others' experience also suggest that?

At all events, a highly enjoyable and interesting exercise.

All best as ever   Martin Wainwright  Thrupp, Oxon


  1. Hello Martin, unlike (say) our GPS, the pheromone/antennae arrangement for getting these moths together is quite a simple and basic arrangement and the final meet-up between male and female Emperor can sometimes be quite a protracted affair especially if there's a fair amount of gusty wind (I have very occasionally seen males give up!). They can obviously tell when they get close to the female because the pheromone concentration must reach a peak and they will lose it when upwind. That seems to cause them to fly in ever-decreasing circles until they've pinned down exactly where she is. Quite a vulnerable time for them as well because they are easy prey for birds at this final stage. In your particular scenario I suspect the breeze had been allowing a concentration of the female's pheromone to build up inside your shed (from where it would have had no escape) so, "following their noses", they might have assumed that's where she was during this final stage. As you say, once in there they would have had some difficulty finding a way out.

    While on the subject of "assembling", I don't know who else is likely to read this but a lot more people seem to have been trying to record Emperors over the last couple of years now that there's a synthetic lure available to purchase. Many seem to be under the impression that the males will only fly on warm, sunny days. This is definitely NOT the case! I haven't tried when it has been raining but my experience is that even on cool, overcast days if the males pick up the pheromone they will respond. A moth that chooses to fly in April is hardly likely to be too fussy about the weather...

  2. I have recently purchased the Emperor lure, and the accompanying notes from ALS do refer to hanging it out on a sunny day, thus perhaps implying that the lure may not be as effective on a cloudy day. Also, the notes state that the lure must be kept dry, so I guess rain is best avoided.
    I have tried the lure in my garden on a couple of occasions, so far without success. This is no doubt due to a lack of Emperors in my area, rather than any fault with the lure. In fact, in the few years I have been studying my garden moths, the only live Emperors I have seen have been ones hatched from pupae kindly given to me by our very own Martin Wainwright. Still, I live in hope that a truly wild Emperor will appear at some stage and I can finally add it to my garden list.

  3. Hi Steve, yes the synthetic lure needs treating with care (especially with regards to the possibility of condensation forming immediately after removal from the freezer) but the female moth has no such problems! I imagine that she would simply stop "calling" if it started to rain. I'm sure that with some perseverance you stand a good chance of getting a garden record. I don't know what the situation is like in Berkshire as all my assembling work has been carried out in Bucks and mostly in the northern half of the county, but I did have a result at Littleworth Common in 2012 which is only about 3 miles east of Cookham.

  4. Steve, I've assembled Emperor in Maidenhead (I haven't tried this year). About the same distance away as Littleworth Common, but in a different direction. So I'd say keep trying.

  5. Sorry to be late in thanking you very much for that interesting info Dave, but it's also good to catch up with Steve and Martin's activities. I still have two unhatched cocoons from May 2014, I think - I say 'I think' because I'm not entirely sure whether they are full or empty. But if anyone would like them, I have had enough of Emperors for now (in the nicest possible way). To save anyone a wasted journey, I could try a bit harder to find out whether they are still inhabited, with a magnifying glass or whatever. They may of course have perished but, if so, they'd be the first of the whole 25 to suffer that fate. All v best M


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