Leaf Beetle - Chrysomelidae Family
Iridescent Beetles
This week I spotted two of these tiny (1 cm) beetles on a Silk Tassel Bush! They didn't look like anything in my field guide, so I posted them on bugguide.net. Right away they were identified as Leaf Beetles, in the Chrysomelidae Family. Their brilliant, metallic, blue-green color was amazing!!! It made me wonder what causes this iridescence, or "luminous colors that seem to change when seen from different angles." It occurs naturally in some beetles, some butterflies, and some birds. The color is not from pigment, but rather from structure. Interestingly, the color works as camouflage, not as warning to a predator or as an advertisement for a mate!
Leaf Beetle - Chrysomelidae Family
The following information from http://www.webexhibits.org/ explains how this coloration works.
"The epicuticle, or outermost surface, of iridescent beetles is made of many stacks of slanting, plate-like layers, which are oriented in different directions. These layers bend, and then reflect the incoming light in the same way as the ridges of iridescent butterfly and moth scales. A layer of pigment below the refractive plates of beetles and the ridges of iridescent butterfly scales enhances the effect of the iridescence. In some species, the epicuticle acts as a reflection diffraction grating to cause iridescence.
Most insect structural colors are in the green-blue-violet range, but red, gold, and copper colors may also be produced in this way. The shade of color and its intensity are determined by several factors, including the thickness and spacing of the layers of the scales, or epicuticle, the number of these layers, and the angle of the incoming light."
The following information from
explains how this coloration works as camouflage!
"Some beetles have beautiful, shiny carapaces [hard outer shell] that look like metal, or a jewel. That shininess is called iridescence. It's caused when tiny structures in the carapace interfere with certain wavelengths of light, so that different colors are seen from different angles.
It’s actually fairly common in insects, and the feathers of some birds, too. Beetles don't use the bright, shiny colors to attract a mate, because in most species iridescence is found in both sexes and during non-reproductive stages of the insect's life. Neither is irridescence used as a kind of warning to predators, because most iridescent beetles aren't poisonous.
The best experiment would be to test whether predators are better at finding iridescent of non-iridescent targets, which is what they did next. They took the wing cases of iridescent and non-iridescent beetles and baited them with a tasty mealworm. They put out more than 800 targets like this in a wooded area.
Birds found and ate 85 percent of the non-iridescent targets, but only 60 percent of the iridescent ones. Humans also found the iridescent targets harder to find. The iridescent targets were especially hard to find on glossy leaves. So, as unlikely as it may seem, iridescence is an effective form of camouflage."
Anna's Hummingbird (male) flexing it's tail and wings! - Calypte Anna
"Joyas Voladoras" - Flying Jewels
This week some Anna's Hummingbirds showed up, with the males displaying their amazing, metallic, iridescent colors! Iridescence in hummingbirds is structurally different than iridescence in beetles. Their iridescence is formed in the bubbles found in their pigment producing melanosomes! What??? An article posted below explains this process. Before you read it, I wanted to share part of an essay that one of my favorite authors, Brian Doyle, wrote about hummingbirds. Just Google "Joyas Voladoras" by Brian Doyle to read the whole essay, it's beautiful!
"Consider the hummingbird for a long moment. A hummingbird’s heart beats ten times a second. A hummingbird’s heart is the size of a pencil eraser. A hummingbird’s heart is a lot of the hummingbird. Joyas voladoras, flying jewels, the first white explorers in the Americas called them, and the white men had never seen such creatures, for hummingbirds came into the world only in the Americas, nowhere else in the universe, more than three hundred species of them whirring and zooming and nectaring in hummer time zones nine times removed from ours, their hearts hammering faster than we could clearly hear if we pressed our elephantine ears to their infinitesimal chests."
by Brian Doyle
Anna's Hummingbird (male) - Calypte Anna
The following information at https://www.sciencedaily.com explains how iridescent colors occur in hummingbirds.
"Hummingbirds are some of the most brightly-colored things in the entire world. Their feathers are iridescent -- light bounces off them like a soap bubble, resulting in shimmering hues that shift as you look at them from different angles. While other birds like ducks can have bright feathers, nothing seems to come close to hummingbirds, and scientists weren't sure why. But a new study in Evolution shows that while hummingbird feathers have the same basic makeup as other birds', the special shape of their pigment-containing structures enables them to reflect a rainbow of light.
All birds' feathers are made of keratin, the same material as our hair and nails, and they're structured like tiny trees, with parts resembling a trunk, branches, and leaves. The "leaves," called feather barbules, are made up of cells that contain pigment-producing organelles called melanosomes. We have melanosomes too -- they produce the dark melanin pigment that colors our hair and skin. But pigment isn't the only way to get color. The shape and arrangement of melanosomes can influence the way light bounces off them, producing bright colors.
In birds, you get layers of melanosomes, and when light bounces off the different layers, we see bright colors.
But even among birds, hummingbird melanosomes are special. Ducks have log-shaped melanosomes without any air inside, but hummingbirds' melanosomes are pancake-shaped and contain lots of tiny air bubbles. The flattened shape and air bubbles of hummingbird melanosomes create a more complex set of surfaces. When light glints off those surfaces, it bounces off in a way that produces iridescence."
Orb Weaver Web showing iridescence
Iridescent Spider Webs
Before the rains, I saw lots of spider webs in the forest this week. Often they were shimmering and iridescent. The following information from https://gizmodo.com explains how iridescence forms in spiderwebs.
"What we're seeing is the result of diffraction. A strand of spiders silk is only two to three times the size of a wavelength of visible light, so the two interact significantly. When a wave of light hits the web, it gets scattered in many different ways. The wave moves around the web, or it gets reflected by the web, or it sometimes moves through the material of the web. Exactly what happens depends on the angle of the light, the thickness of the specific strand of web, and the slight imperfections in the surface in the strands of the web."
Scarlet Fritillarly - Fritillaria recurva
Damp Earth Art
Over the past two weeks, we've received over 8" of rain!!! WOW!!! What a miracle! Everything is bejeweled and sparkling with raindrops! Such amazing beauty! Here are some of the jewels I found in the forest! Enjoy!
Sky Lupin up close - Lupinus nanus
Please join me in my continuing hope for precipitation! Perhaps our collective efforts may help it happen. I'm going to keep posting rain inspired writings, art, etc. on my blog at dampearthart.blogspot.com. Any submissions would be greatly appreciated.
North Yuba River - October 2021 and April 2022
The river picked up quite a bit these past two weeks! The current flow rate is 2,400 cfs (cubic feet per second), and the height is 6.5'! The last time I checked out the measurements was in January, 2022, and the flow rate was 445 cfs and the height was 3.5'!! Yahoo!!
Wishing for peace in Ukraine and
an immediate end to this senseless war!
Wild Turkeys (female - male) - Meleagris gallopavo
Just before the storms arrived, we were up in the Lakes Basin and to our total surprise we came across a pair of Wild Turkeys!!! We've never seen any Turkeys in the Lakes Basin before, although I've since read that it's not that unusual. It probably snowed a few feet up there this past week. I wonder if the Turkeys survived. Fingers crossed!
Where are the Bear and the Deer?
What's happening in the roadside ditch?
What songbirds have recently arrived?
Check back next week for the answers to these questions and more!
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