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Dave
Of course that doesn't quite work when you think about this behaviour in terms of natural selection acting at the level of the individual (i.e. the caterpillar) - each caterpillar has to 'decide' (except it's probably not a conscious decision) what to do, and the mother can't say 'a quarter of my eggs will pass the winter this year'. I imagine that each caterpillar can decide whether to emerge with the rest - a very safe strategy, but one that means it will be exposed to loads of competition for resources from the others in its cohort - or to pass the winter - a very risky strategy, but one that pays off (if successful) with much-reduced competition. When a caterpillar tries the overwintering strategy and it pays off, its offspring might be predisposed to also try that strategy. By this means the overwintering strategy will pay off just often enough for some individuals in the population to continue to try it.bugboy wrote:It would seem a simple case of not putting all your eggs in one basket kind off scenario, keep a few back in case the main late summer brood fails for whatever reason.
I always thought that butterfly adults were inactive in cold periods, because they need a lot of warmth to get their flight muscles going. If you're ever emptied a moth-trap the following morning, you'll have noticed the moths sit and vibrate their wings hard for a few seconds (or even up to a minute) before flying off, which I believe is for the same purpose - generating metabolic heat to transfer to the flight muscles. That might mean that the thermal threshold needed by the immature stages to become active might be far lower. One of the metrics that we often use to estimate, effectively, 'available development time' for Lepidopteran larvae is 'growing degree days' which counts degrees celsius per day above a lower threshold - which we usually set as low as 5 degC. Setting it higher (even at 10 degC) means that some of the earliest spring moths appear to have emerged after zero development time (which is obviously incorrect!).Pauline wrote:Whether they hatched during the evening or overnight I am still intrigued as to where they got the energy. They are such tiny little creatures and given that butterflies are inactive in cold periods how does that work?
Hi Pauline, a few general thoughts on the subject from me also.Pauline wrote:The first question I have concerns the 2 BH eggs that were in the process of hatching late in the day. I wished I could have stayed to determine exactly when these eggs hatched but when I left it was cold and cloudy (as it had been for most of the afternoon). Whether they hatched during the evening or overnight I am still intrigued as to where they got the energy. They are such tiny little creatures and given that butterflies are inactive in cold periods how does that work? Whilst it may well be a good survival strategy (fewer birds around at night and other predatory insects inactive) I am still puzzling over this.
Pauline wrote:I think that Bugboy was implying the same as you ie, it is not the butterfly's choice but the caterpillar.
CallumMac wrote:Pauline wrote:I think that Bugboy was implying the same as you ie, it is not the butterfly's choice but the caterpillar.
Yes - sorry, in hindsight it does sound like I was contradicting him, but I didn't mean to be! I agree that we were largely saying the same thing, but I just wanted to clarify that the 'decision', such as it is, is taken by individual caterpillars rather than as a collective.
bugboy wrote:If many more pictures of Dave appear on here we might have to set up a species specific page for him too![]()
bugboy wrote:If many more pictures of Dave appear on here we might have to set up a species specific page for him too
It must have been in his pocket, either that or witchcraft...there is no other answerPauline wrote: Dave and I had been chatting for some time about everything butterfly related when of course the subject came round to Holly Blues. We hadn't seen one at all during the day and I suggested to Dave that perhaps he should have brought a handful with him. I had no sooner got the words out of my mouth than a Holly Blue flew past and landed at Dave's feet???![]()
Honestly, what's the chance of that happening?????