Color me green!

When I went out to pick raspberries this morning, I found something much more delightful than a bunch of mating Japanese beetles (the scourge of the berry patch!) — a couple of 1-inch Gray Treefrogs hiding in plain sight on the green leaves of the raspberries.

From the side, this little one with its dark facial markings and dark lateral stripe was more obvious.

Although this species is named the Gray Treefrog, because they are quite gray with a dark blotchy pattern sometimes, in bright sunlight on a green background, they are well camouflaged as they match their background. In fact, this frog even matches the particular shade of green of the raspberry leaf on which it rests.

I wonder if they eat Japanese beetles? There are plenty of other insects resting on the raspberry leaves for these little guys to dine on. But these frogs are really only active at night, and usually seek shaded vegetation for their daytime rest.
The color matching camouflage is impressive in both the shade (this photo) and the sun (photo above).
How exactly does a gray treefrog become green?
Looking more like the gray treefrog, I photographed this maxi-sized (2.5-inch) adult in the early morning while it was sitting under an evergreen in the leaf litter.

Frog skin contains a stack of color-producing cells called chromatophores, and many frog species like the Gray Treefrog, have 3 sets of them: a deep layer called melanophores that contain a black/brown pigment called melanin, an intermediate layer called iridophores that lack pigment but contain particles that can reflect blue light, and an upper (most superficial) layer called xanthophores that contain yellow pigment.

Now, it should be more obvious how a Gray Treefrog can transform quickly from its gray color that is produced by the dispersion of deep-lying melanin pigment to a bright green color, produced by the interaction of blue-reflected light from the iridophores passing through the yellow pigment of the xanthiphores (i.e., blue plus yellow equals green to our eyes).

The dispersion of pigment in frog skin is controlled by nerves and hormones, which act on the chromatophores to aggregate (condense) or disperse pigment. Physiologically, in a matter of seconds, when melanophores aggregate their pigment to uncover the iridophores and xanthophores disperse their pigment, a gray frog turns green!

Color changes can even happen while frogs are sitting in the dark in my covered water tank. It just depends on their physiological state, the temperature of their environment, and the amount of hormonal or nerve stimulus they are experiencing.

Chameleon spider

When I was out picking raspberries the other day the other day, I found a pretty little white spider waving its long front legs at me.

Flower crab spider, Misumena vatia

This little crab spider waving its front legs should look like a tempting morsel to a bird.

Getting closer, I see that this is a crab spider, an ambush predator that sits and waits for prey to come near and then reaches out to snare them with its long front legs.

Flower crab spider, Misumena vatia

Crab spider in ambush mode with front appendages spread to snare unsuspecting prey.

Flower crab spider, Misumena vatia

Spines or spurs at the ends of those long appendages help snare the unsuspecting prey.  Maybe a Japanese beetle will land close by;  there are plenty of them on these raspberry plants.

Japanese beetles eating raspberry leaves

There are plenty of these little beasts chewing up my raspberry bushes, but I don’t know if the spider is even interested in them.

I’m intrigued by the strawberry colored marking on the sides of this little spider, which should make it easy to identify.

Flower crab spider, Misumena vatia

A Google image search suggests this is a flower crab spider, or goldenrod crab spider.

Usually, these flower crab spiders are well camouflaged by matching the color of the flower, yellow or white, on which they are sitting.  The white-flowered raspberries have finished blooming, however, so this crab spider stands out against green leaves and red fruit.  Time for it to move to the back yard and start hunting on the yellow oxeye, black-eyed susans, and yellow coneflowers.

Goldenrod crab spider capturing a wasp.  From Wikimedia Commons

Goldenrod crab spider capturing a wasp. From Wikimedia Commons.

In its yellow form, the crab spider blends perfectly with its background on the flower, but how does a white spider turn yellow?  By secreting yellow pigment from the top layer of cells in its outer covering into the white, pigment-containing cells below, flower crab spiders can be chameleon-like, changing gradually over a period of 10-20 days from white to yellow.  Yellow spiders that move to white flowers excrete their yellow pigment and transform into white spiders in a mere 6 days.

Flower crab spider, white morph, Photo from Wikipedia

Flower crab spider, Photo from Wikipedia, by Luc Viatour, https://lucnix.be/

Visual input is highly important in stimulating and achieving the spider’s color matching to its background; spiders whose “eyes” were painted over lost the ability to change color.

Apparently, only the females are the chameleons of this species; males which are a small fraction of the size of the females, are yellow-brown and cannot change color.

green on green

Hiding in plain sight by matching the color of your skin to the color of the background is useful for predators stalking their prey or prey trying to escape predation.  It’s also useful in confusing photographers about where to aim their cameras.  Case in point: I saw the bushes moving, wondered if it was a bird, thought it might be a chipmunk, but stared right at the little critter for a full minute before I figured out what it was.

gray tree frog-

A gray tree frog in green phase hiding in plain sight.  It wasn’t this obvious without the zoom on the camera to help pinpoint its location.

gray tree frog-

It’s scientific name gives a hint to its ability to change colors: Hyla versicolor. Usually it appears mostly gray with green splotches.

Many species of fish, amphibians, and reptiles have the ability to change color and outward appearance by contracting or expanding the chromatophore (pigment-containing) cells in their skin.  This chameleon-like ability can assist them in better regulating their body temperature, or as suggested, in achieving the kind of camouflage that helps them evade their predators or fool their prey. It is thought that the animals’ eyes perceive the color spectrum of their environment and send neural signals to skin chromatophores to effect the appropriate color changes.

In cases where there doesn’t seem to be a clear message about the color of the background, Gray Treefrogs are often mottled gray and green, or just remain gray, as illustrated below.

gray-tree-frog-

Hmm… water in a bird bath? Not sure what color to be.

gray-tree-frog-

Gray treefrog sitting on the side of a dish pan, next to green vegetation — again, it’s confusing about what color to be.

gray-tree-frog-

Gray treefrog sitting on an orange dahlia — no possibility of a match here.

gray-tree-frog-green-phase

Green-colored Gray treefrog on the ledge of a wooden door? Clearly a bad match.