As promised in the last posting, I'm going to continue talking about beautifully blue animals and, as in our exploration of blue feathers, virtually none of the sky-coloured feet, beaks, skins, and insect parts that follow have any blue chemicals to thank for their hues. All are due to scattering of light by fine particles suspended in liquids, or by carefully ordered layers of collagen fibres, or thin layers of scales precisely spaced, or parallel ridges that reflect and emphasise blue light. The physics of most of it is beyond me I'm afraid - fortunately this is not a physics blog! However if you're mathematically minded, this might be of interest.
Bearing the general principles in mind, here is a tour of some of nature's blue bits.
Image may be NSFW. Clik here to view. ![]() |
Poison Dart Frog, family Dendrobatidae, Ecuador. (Don't try this at home, or anywhere else, incidentally! Local people seem to acquire an immunity to these stunning but potentially deadly little frogs. I've heard of visitors getting very sick from handling one.) Frog skin colours are very complex, with often three layers of different cells in the skin. In the case of blues, iridophores sit above melanin-filled melanophores; the iridophores reflect blue light back, like iridescent feathers that we discussed last time. |
Image may be NSFW. Clik here to view. ![]() |
Male Gippsland Water Dragon Itellagama (Physignathus) lesueurii, National Botanic Gardens, Canberra. |
Image may be NSFW. Clik here to view. ![]() |
Unidentified skink, Cooktown, north Queensland. Any assistance gratefully received! |
Image may be NSFW. Clik here to view. ![]() |
Male agamid, Queen Elizabeth National Park, Uganda. |
Image may be NSFW. Clik here to view. ![]() |
Southern Cassowary Casuarius casuarius, Wallaman Falls north Queensland. (Taken through a car window!) |
Image may be NSFW. Clik here to view. ![]() |
Blue-faced Honeyeater Entomyzon cyanotis, Griffith, New South Wales. |
Image may be NSFW. Clik here to view. ![]() |
Blue-footed Booby Sula nebouxii, Puerto Ayora, Galapagos. The bluer the feet, the more attractive the owner to the only one who matters. |
Image may be NSFW. Clik here to view. ![]() |
Andean Ruddy Duck Oxyura jamaicensis, El Calafate, Argentina. |
Image may be NSFW. Clik here to view. ![]() |
White Tern Gygis alba, Lord Howe Island. |
Image may be NSFW. Clik here to view. ![]() | ||
Dusky Woodswallow Artamus cyanopterus, Canberra. |
Image may be NSFW. Clik here to view. ![]() |
Leaf Beetle, Chrysomelidae, possibly a cryptocephaline (the cylindrical leaf beetles) Whyalla, South Australia. I have no idea about this beautiful chewer in particular, but in some blue beetles at least layers of disc-shaped scales in the cuticles are responsible. (My thanks to Susan for helping with the family.) |
Image may be NSFW. Clik here to view. ![]() |
Painted Locust Schistocerca melanoceraSierra Negro volcano, Galapagos. Like so many other Galapagos residents, they are found nowhere else. |
In dragonflies, the system is similar, with Tyndall scattering of light from particles suspended in a waxy layer above a dark cuticle layer.
Image may be NSFW. Clik here to view. ![]() |
Tropical Rockmaster Diphlebia euphoeoides, north Queensland. |
Image may be NSFW. Clik here to view. ![]() |
Black-headed Skimmer Crocothemis nigrifrons, Canberra. |
Image may be NSFW. Clik here to view. ![]() |
Shining Oak Blue Arhopala micale, Cairns, north Queensland. |
Image may be NSFW. Clik here to view. ![]() |
Satin-Green Forester (Pollanisus viridipulverulenta, Yeldulknie Conservation Park, South Australia. Its iridescence makes it flash from green to blue, depending on the angle. Don't sniff too deeply - its family, Zygaenidae, specialises in releasing cyanic acid in self-defence! (My thanks to Susan for putting me on the right track to identifying this one by recognising the family.) |
Image may be NSFW. Clik here to view. |
Urania Moth, Manu National Park, Peru |
Image may be NSFW. Clik here to view. ![]() |
Euchromia creusa, north Queensland. Here the blue is not (mostly) in the wings, but in body scales. Presumably the principle is the same however. |
Image may be NSFW. Clik here to view. |
Sally Lightfoot Crab Grapsus grapsus, Galapagos. |
Image may be NSFW. Clik here to view. ![]() |
Soldier Crabs Mictyris longicarpus, Cullendulla Creek Nature Reserve, New South Wales |
EITHER WAY, BACK SUNDAY