Regularities

Cleavage planes! I’d heard of this from my earliest classes on the crystallization of salts. Apparently, if you take a crystal and give it a sharp tap it will break neatly along a plane. Before modern techniques like x-rays, people used these planes to guess at the symmetries of crystals. Unfortunately I never had a large enough crystal to try it with. So I was quite thrilled on a walk in Bhutan when I noticed that the blasts which had cleared the hillside for the road had resulted in a clear cleavage plane. I took this photo edge on, so the plane shows up as the discontinuity along the middle of the photo. The tap that breaks a crystal, salt or rock, can be delivered either by a hammer or by a stick of dynamite.

I first noticed the regularity with which this moth had laid its eggs on the glass while I sat inside a moving bus and watched the moth cling to the outside of the window. When we stopped I got down to take a photo. The first instinctual identification from a group of people from the western Ghats is the Handmaiden moth (Syntomoides imaon). That is also what Google Lens says. But this is wrong, as you can see by comparing it with curated images on Moths-of-India. One possibility is that it belongs to the genus Caeneressa, of which only the species C. diaphana ranges as far west as Bhutan. But this is a sheer guess. Apart from the identification, the regularity of the array of eggs is interesting. It seems that the moth lays eggs as it sweeps its abdomen from side to side, moving outward (or inward, I did not see which) as it reaches the extreme ranges of its swing.