Tag: color (Page 1 of 2)

Bug of the Week: Cochineal Scale

Can you find the insect in these photos?

cochineal scale

cochineal scale

If you guess the white fuzzy, waxy stuff might be a clue, then congratulations. Believe it or not, the insect we are going to explore today has been the subject of greed, subterfuge and may have helped our forefathers defeat the British during the Revolutionary War. Not quite what you’d expect from a tiny insect that spends its life feeding on cactus pads hidden under some white fluff.

When the Spanish explorers first came to the New World they discovered the natives were wearing bright red garments. They were amazed, because no color like that could be found in Europe. The Mixtec people had been culturing a tiny insect, called the cochineal scale, as a way to produce a wondrous dye.

The cochineal scale insects live on the pads of certain prickly pear cacti. I’m not even sure how the early Mixtecs discovered the red body of the scale, because all you see on the surface is white fluff. Underneath is a small blob that looks like a pinkish seed. Within the body, the hemolymph is deep red. Although I doubt you can see it, there are few drops of this red where a bird or something has pulled the scale from out of the waxy covering in the left, center of the photographs. (Someday I hope to get some better photos, but this was at a public garden and I didn’t want to disturb nature. As usual, The Firefly Forest has a good photo if you want to see another example.) Somehow the Mixtecs found the cochineal scale, however, and they figured out how to process them into a red dye.

The Mixtecs farmed the insects with skill and care. They would plant cactus pads infested with the scales, weed the plants, build walls to keep animals away from the plants, and even shelter the plants during rain showers so the insects wouldn’t get washed away. Then they would carefully collect and dry the female scales to make the dye powder. It was a hugely labor intensive process. Not to mention that the cactus pads were covered with painful spines, which had to be avoided.

Many people in Europe wanted the dye and there was a limited supply. At first, only the very rich and powerful could wear it, like kings and queens, or the bishops and cardinals of the Roman Catholic Church. By the year 1600 cochineal dye was an extremely valuable export from Southern Mexico. Gold was the only export from the region worth more money. Dried insect bodies were worth more than silver!

The Spanish went to great lengths to keep the origin of the dye a secret. In fact, the results of their subterfuge can still be found on the Internet today. You can find websites that mention the “cochineal beetle.” In the past, people thought the secret insect might be a beetle and this misidentification has survived until today. See this webpage, for example. Scale insects are flat, legless and have sucking mouthparts. Beetles are rounded, have hard wings called elytra, prominent legs and chewing mouthparts. Cochineals are scales for sure. Oops. And by the way, the insects make the red coloring within their own bodies, they do not obtain it from the red fruit.

Eventually the dye was used to color the “redcoats” of the British army during the Revolutionary War. I have read that our soldiers were able to recognize and selectively fire upon the high-ranking soldiers, because only the elite got to wear the bright red cochineal-dyed uniforms. The foot soldiers uniforms were dyed with a cheaper dye that gave a duller color. Thus, the officers were easy to spot.

In the 1870’s, synthetic red dyes were developed and they began to replace cochineal for widespread use. Cochineal in the United States is now largely used as a food dye, found in such products as sausages, candies, and juices, as well as cosmetics. Check some of the ingredients of pink fruit drinks at your local grocery and look for the word “cochineal.” You may have been appreciating these wonderful insects when you drank juice and you didn’t even know it.

Colored Clouds

Are you interested in weird clouds and unique weather? Although you might think we wouldn’t have that many clouds here in the desert, during the late summer we have spectacular, sometimes violent, thunderstorms called “monsoons.” These storms can produce some highly unusual formations.

Last summer some friends and I were swimming in an outdoor pool. We were watching the sky carefully because a monsoon storm was approaching and we didn’t want to get caught in it. The sun was starting to go down when we noticed the most amazing colors in the clouds. We didn’t see the usual rainbow colors, however, not the vibrant red-orange-yellow-green -blue-indigo-violet in an arch. Instead, these were the colors you would see in a pool of oily water. We saw greenish-blues, teals and magenta hues. The colors were all over the clouds, too, not like the small pieces of rainbows we call sundogs.

I wrote to a local expert asking about it, but I never heard anything back. I figured it was something like an airplane dumping fuel (it was right near the airport) had caused it, and that I’d never see it again.

This weekend, however, I found a webpage at The Firefly Forest with photos and an explanation. The author, T. Beth Kinsey calls them iridescent clouds. Aren’t they amazing? Take a look and let me know what you think.

Weekend Science Fun: Exploring Fall Color

Coming from a place where the leaves on the trees turned brilliant colors each fall, I guess having the calendar say that it is fall made me yearn for some color. Is there any better way to get children outside than to go check if any tree leaves are turning their autumn colors yet?

During your trip you or your children may have some questions about the whys and wherefores of leaves turning yellows, oranges, reds, and maroons.

Most trees have green leaves during the growing season. Look closely, however, and you will notice not all the leaves on a tree will be the same color. New leaves will be a lighter, brighter green. Older leaves will be dark green. Leaves that are about to fall off are yellow.

How do scientists study the colors in plants? One way is to perform a simple color separation or “chromatography.” The materials that reflect or absorb certain colors when subjected to light are called pigments. In the following test, we are looking for the pigments found in growing plant leaves.

The chromatography does require some time, at least an hour, so prepare your children in advance. It also requires rubbing alcohol. I tried to use water as a solvent instead and it just didn’t work.  Note: If you are working with small children around, make sure they won’t try to taste the mixture, because of the rubbing alcohol.  Read and follow the warnings on the label carefully.

You will need:

  • A spinach leaf per child (spinach is full of pigments)
  • Small clean containers, like a yogurt cups or jars  (paper leaks) for one per child
  • Tool to chop the spinach leaves (requires adult supervision)
  • Rubbing alcohol (adult should pour)
  • Stirring utensil that will fit in containers
  • Coffee filter cut into about ¾-inch-wide strips that will fit into the container from top to bottom, one per container

Chop up the spinach leaves into tiny pieces. Put the chopped bits into the bottom of the containers. They should cover the bottom in a layer, up to ¼-inch deep. An adult should pour in just enough rubbing alcohol to cover the leaf bits. Stir a few seconds. Slide the coffee filter strip into the container, so that the bottom touches the alcohol/leaf mixture. Rest it against the side. Now wait for about an hour.

The alcohol should slowly move up dry part of the coffee filter, carrying the pigments as it goes. The heavier pigments will travel more slowly, the lightest most quickly. Once the wet alcohol front nears the top of the strip of coffee filter, remove it. Check the colors. Lay it on a piece of paper towel or paper and let it dry a bit. Often the colors of the pigments will show more intensely once the alcohol has evaporated.

Your coffee filter might look like this:


The green bands at the bottom are chlorophyll pigments. The plant uses chlorophyll to convert the sun’s energy into food. If you look closely, there are two bands of green, with some yellow. Those are the two chlorophyll pigments, named chlorophyll a, and chlorophyll b.

Just above the green is an intense yellow band. The yellow is a group of pigments called xanthophylls. Xanthophylls make corn yellow. When chickens eat plants with xanthophylls, they can use it in their eggs to make the yolk yellow.

At the very top, is a thin orange band. Those pigments are carotenes, named for the first plant tissue they were isolated from, carrot roots.  Carotenes are also found in pumpkins and squash.

Now compare the colors in the growing spinach leaf to those of the autumn leaf. What colors are the same? What colors are missing in the leaves? What colors are in the leaves but not in the spinach?


First I notice very little green in the autumn leaves. The chlorophyll pigments break down in the fall leaves. I do see the oranges and yellows. The carotenes and xanthophylls have been there all along in the growing leaf, but masked by the deep green. When the green disappears, we can see them.

I see another color, however, that wasn’t present before, an intense red. The red pigments are called anthocyanins, and are known for making flowers, and vegetables like beets, red or purple. It turns out that certain trees make a lot of anthocyanins in their leaves in the fall. It wasn’t there earlier in the year.

Right now scientists don’t know for sure why certain types of trees produce the anthocyanins. One suggestion is that the anthocyanins act like sunscreen to help protect the leaves while the last bits of nutrients are being moved out and down to the roots for storage over the winter. Another suggestion is that red trees are less visible to insects. Harmful insects may lay their eggs on trees in the winter, and may choose trees that are yellow over those that are red.

In any case, aren’t the colors amazing?

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