Now is the time I pull it all up, “nuke” the weeds, and start over. This is how I spent last weekend.
I was pulling out the tomato cages and uprooting the dead tomato plants, when I noticed a peculiar thing. A tomato plant’s stem was covered with a shell of dry mud. The shell was fragile and when I touched it, the dry mud broke apart. Inside was the stem, but it looked odd. It seemed like it had been scraped down to the plant’s “bones.”
Of course, plants don’t have bones. It was just the tough, white, inner fibers of the stem that I saw. But I was curious: What could have made such a mud tube all around the stem? Was this the work of some space alien?
I found out. Termites! But they are not the standard house-eating kind of termites. These are desert termites. They live underground and are found throughout the drier parts of the Southwest. To feed, desert termites build mud casings around the stems of dead plants and grasses. Inside these protective tubes, the worker termites eat the surfaces of the enclosed stems.
The cellulose (plant fiber) that the workers eat is the food for the entire colony. But cellulose is difficult for most animals, including humans, to digest. Cellulose passes through an animal’s gut undigested. Think of the dietary fiber our doctors encourage us to eat. Its purpose is to keep things moving along. It adds bulk, but no nutrients.
So how do termites break down plant fiber to get at the food energy it contains? They have help. Inside the intestines of termites live some tiny, one-celled animals called protozoans. These little guys produce the enzymes that break down cellulose.
It’s a symbiotic relationship in which both members of the arrangement benefit. The termites get energy and nutrients from an otherwise unusable substance. The protozoans get food, moisture and protection from the dry and dangerous outside world. You can’t get much better protection, if you are tiny, than to be inside the gut of an animal!
Breaking down cellulose is a good thing for Earth, too. There are a lot of plants, thus a lot of cellulose. And more is being produced all the time. When cellulose is broken down, a food chain is completed, and carbon atoms are recycled.
Desert termites go one step further with their recycling. There is good nitrogen-rich fertilizer in their feces. And they use it as a building material, too.
How and why do desert termites make those mud tubes? Keep in mind where these termites are found: the desert, right? To protect the soft-bodied insects from dehydration, they must have some sort of cover when they are not in the ground. So they build the tubes from silt and their own feces. It all sticks together nicely and quickly hardens into a tunnel around the vegetation. When the workers come up to feed on the stems, they have cool, protective chambers in which to forage. If you break open one of the tubes in the early morning you can sometimes see the termites at work.
The king and queen termites start off as winged creatures. After a summer rain, these alates (the winged ones), as they are called, rise up into the air in swarms. In the swarm, the males and females pair up and then fall to the ground. There they shed their wings (or bite them off!) and go off to form new colonies.
Although desert termites promote recycling of nutrients, there are conflicting opinions as to their value to farmers and ranchers. One source says they benefit the soil by making it more porous and enrich it with their home-made fertilizer. However, some researchers report that at times most of the termites’ diet is live grasses, not dead plants. This would put them in conflict with other grass-eaters.
The real problem lies with lack of water. Much of West Texas is perpetually “droughty.” It is easy for the dry rangelands to be overgrazed. Some studies show that the combined biomass of all the desert termites in arid rangeland soil outweighs the biomass of all the cows on the surface! But is it a case of too many termites or too many cows?
Drought conditions favor the desert termite. This is why we are seeing so many of the mud tubes in our dry South Texas pastures this year. If you have never seen the desert termites’ mud tubes, I think you will. What a busy world lies beneath our feet!