Stinkbugs, Indian corn, Meanders

Q:  I see stinkbugs out on the desert, and wondered:  how hot can they get, how tough are they and what do they drink?  April, Albuquerque, New Mexico

Darkling beetle poised to fire hot, noxious chemicals — normally at a predator — but this time at the photographer. Photo courtesy of Troy Bartlett, © 1999 used with permission.

All right.  I confess.  This is my question, but I got curious, out on the desert watching what I call a stinkbug trot across the hot sand.  It turns out desert species of the insect can stand temperatures up to 120° F (50° C); they seek shade in the hottest part of the day.  Running on long legs keeps them, not exactly high, but a safe distance from burning sand. 

Stinkbugs, more conventionally known as darkling beetles (named after their dark color), are tough, especially those adapted to deserts.  Sticking a specimen pin through a darkling beetle sometimes fails.  "It's as if the insect were made of metal," says Georges Brossard of Insectia. 

Although darkling beetles eat mostly dry food (dried or rotting plant residue), some darkling beetles never actually drink water.  Instead their bodies separate water from the food they eat.  They can even get water molecules from dry flour.  Once they have it, they keep it.  Several layers of a waxy substance coat their exoskeleton (body armor), and trap the precious water.  Their wings, fused to their body, also prevent water loss. 

World's biggest sand dune, Namib Desert. Photo courtesy of Wikipedia.

Another species uses her whole body to get a drink of water.  These creatures live in the Namib Desert on the southwest coast of Africa.  The Atlantic Ocean washes along the 1000-mile long, skinny (60-mile wide) desert.  Dunes march to the sea's edge.  In the morning, when the warm, wet sea air meets the cool, dry desert air (still cool from the night before), fog forms and billows over the desert. The darkling beetles of Namib drink fog.  A beetle clambers to the top of a dune, faces the sea, tips her rear end high, lets the fog condense on her cool body, and trickle down to her mouth.  Instead of blasting a predator with her butt high, she peaceably collects water.

Further Reading

Insect external anatomy, legs by John Meyer, North Carolina State University:

Darkling beetle, BBC Nature

Q: Is Indian corn poisonous?  Indu, Greenwood, USA
Q:  Why is Indian corn not edible?  CJ, Minneapolis, Minnesota
Q:  Can you grow and eat Indian corn? Janice, Columbia, South Carolina
Q:  How did Indian corn get its name and why are the kernels hard? Jackie, Franklinville, North Carolina

Indian corn, ready to eat.  Photo courtesy of USDA Agricultural Research Service, by Keith Weller

A: Indian corn is not poisonous, is edible and is an extremely hard corn;  it's a variety called flint corn (Zea mays indurata).  Indians grind the hard corn into flour, and then make it into tortillas.  Popcorn is another variety of flint corn. 

I checked with Eckler Farms to see if it's customary to shellac or treat decorative corn and, thereby, make the corn inedible. 

"We don't do anything to our corn but pull back husks and remove the silks.  It is all natural stuff," says Larry Eckler.  "All you need to do is wash it off with water like you would any other fruit or vegetable."  But stay clear of corn used in potpourri mixes, because those things have added fragrances.

You can grow Indian corn; in fact Eckler Farms sells seeds, or you can pick them up at your local nursery.

Indian corn got its name from Central and South Americans Indians who first cultivated corn at least 5600 years ago.  Why it is hard? Unlike the sweet corn we usually eat, the exterior of flint-corn kernels is hard and completely encloses the soft starchy part (the endosperm).  Sweet corn kernels have a soft exterior as well as a soft, starchy inner part.

By the way, Eckler suggests popping mini Indian corn.  "It's really good." 

Further Reading:

The different kinds of corn, The International starch institute

How Indian corn defies Mendel's principles of genetics, by N.V. Federoff and Wayne's Word, an online textbook of natural history, Palomar College

Why Indian corn is colored by April Holladay, WonderQuest

Gourds, Indian corn, seeds and fall decorations by Eckler Farms

Q: Why are river meanders shallower on the inside and deeper on the outside?  Vickie, Penrith, England

A river cross section showing water dropping at the outside of the bend. Drawing from A Primer on Water by Luna Leopold and modified by the author.

A: A meandering river is one that loops and curves through a wide valley or gently sloping plain.  A curve is shallower on the inside (and deeper on the outside) because the water flows slower on the inside, which allows suspended sand to settle to the riverbed.

As water flows downstream, the water on the surface of the river flows faster than that which drags along the bottom.  Moreover, the water tends to move to the outside of the bend and erode it.  See figure.  At the outside of the bend, water drops down and moves toward the center — like tea leaves as you stir tea in a teacup. The dropping water deepens the channel on the outside of the bend. The water near the bottom roils up bottom debris, and carries clay, sand, and pebbles along with it.  The silt-laden water moves across the riverbed toward the inner bend and drops sediment in the slower-moving water there.  That's what makes the bend shallower in the inside (silt drops), and deeper on the outside (falling water digs a deeper channel).

Further Reading:

Meandering river channels and what causes them, University of Colorado

Meandering river photos, University of Oregon

A primer on water, Luna B. Leopold and Walter B. Langbein. U.S. Geological Survey. U.S. Government Printing Office: Washington D.C., 1960.

(Answered July 18, 2006, updated Aug. 14, 2007)