Friday, 14 August 2020

Fan moth

My electrical caution continues and with good reason. At the end of my Zoom yoga on the lawn the other night, grumbles of thunder were making it difficult to wind down with 'Saraswati Ma' and the first flashes of lightning appeared in the direction of Aylesbury.

Here's the scene an hour later when I carried out a vain search for the far-famed Perseid meteor shower but was rewarded instead with spectacular displays of sheet lightning behind the clouds massed over the Cotswolds. My iPhone has its limitations in such circumstances and it's too late to photograph a lightning flash when you actually see it. But I just kept pressing the button randomly and ended up with all these:



Satisfyingly sinister. In fact, without getting too carried away, not unlike the skies in, say, a painting by Tintoretto, the 'little dyer' whose real surname was Robusti and who was nicknamed Il Furioso because of his vigorous way of painting.  I have just discovered these facts from Google and you may think that I am spinning things out because I have no moths. But I have!  Behold another indoor discovery of Penny's, and a very interesting one:


This is the 20-plume micro, a folding fan of a moth which has the honour of appearing on the back cover of the Micro-moth Bible. The top, very fine picture in the composite is from the totally excellent Nature Spot website based in Leicestershire and Rutland which gets my vote as the best species resource online.  The bottom two are the best I could do late at night in our bedroom which was where Penny found the moth. 

The 20-plume actually has six plumes per wing and should therefore be the 24-plume, but I am not going to quibble. Its caterpillars feed inside the buds of honeysuckle and you have a fair chance of seeing the tiny moth flutter up if you brush past plants at this time of year.

Now, how far do you need to work through this sequence of pictures below to find my second moth?





Yup, it's a Silver Y, as mentioned in my last post. I watched it flying around the last of our peas and sugarsnaps before settling in this position where it is outstandingly well camouflaged. I've often wondered if such an excellent choice of background/surroundings is deliberate and scientific research seems to be suggesting more and more that it is.  Look at this abstract, for example, of a paper about 'visual' senses in caterpillars which do not involve their eyes:


Light sensing by tissues distinct from the eye occurs in diverse animal groups, enabling circadian control and phototactic behaviour. Extraocular photoreceptors may also facilitate rapid colour change in cephalopods and lizards, but little is known about the sensory system that mediates slow colour change in arthropods. We previously reported that slow colour change in twig-mimicking caterpillars of the peppered moth (Biston betularia) is a response to achromatic and chromatic visual cues. Here we show that the perception of these cues, and the resulting phenotypic responses, does not require ocular vision. Caterpillars with completely obscured ocelli remained capable of enhancing their crypsis by changing colour and choosing to rest on colour-matching twigs. A suite of visual genes, expressed across the larval integument, likely plays a key role in the mechanism. To our knowledge, this is the first evidence that extraocular colour sensing can mediate pigment-based colour change and behaviour in an arthropod.

and here is another fascinating piece of research: 

 Bark-resting moths are known for their behavioral background selection for camouflage; they prefer to stay near backgrounds that exhibit colors or brightness similar to their own wing color ( Sargent 1966 ; Grant and Howlett 1988 ), and adopt adaptive resting orientations that reinforce their crypticity ( Pietrewicz and Kamil 1977 ; Webster et al. 2009 ). Recent studies revealed that some bark-resting moths can actively seek out cryptic resting positions and body orientations elaborately after landing on tree trunks by re-positioning ( Kang et al. 2012 ), and they are more likely to do so when the crypticity conferred at the initial landing position is low ( Kang et al. 2013a ). However, previous evidence for this adaptive behavior of moths was based on detection data from non-real predators of moths (humans) and disregarded the specific mechanistic explanations that provided the moths with better camouflage. Here, we use image analysis and avian vision models to identify the concealing mechanisms that are involved in this adaptive behavior of moths. 

I could follow this trail online all afternoon but I have other things to do.  More another time.

1 comment:

Edward Evans said...

Nice peas, our Hurst Green shaft peas have just come into flower and the Echinacea Purpurea is looking glorious.