by Julie L
This tessellation shows translation (slide) symmetry.
The "tile" (tile = repeating shape) is mostly done very neatly, and fits with all the other tiles perfectly, without gaps or overlaps. That's what a proper tessellation does.
Along their left sides and middles, the butterflies look exactly right. However, if you look very closely with an electron microscope and a grumpy disposition, you might notice that Julie could have...and we hope she does... improve this from a good tessellation to an even better one. Making a shape that tessellates, and then deciding it looks like a bunch o' butterflies or a herd of elephants, is just the beginning. After that, I hope all you Escher-style tessellation artist will go back to the "tile" (animal" shape and tweak it.
In Julie's butterflies, maybe she could improve the symmetry between left (purple) and right (blue) wings. The butterflies' wings aren't lined up 100%, horizontally: purple wings stay at the right height; blue wings, though, shift up a little higher on the bodies they're emotionally, if not physically, attached to. Is it pretty enough now? Sure. Would some tweaking pay off? It's up to the artist, of course, but I think it's alllwwwwaaaaays worth trying.