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Bob Henke column: Froghoppers (aka spittle bugs) do not suck

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I just heard a female meteorologist say that the weather for the next week was going to be “sucky.”

One unexpected side effect of mass communication, first in moveable-type printing and more dramatically in all the electronic formats, has been a particularly rapid change in language and lexicon.

Left to themselves, a group’s vocabulary and speech patterns could be expected to remain relatively static and quite in tune with their environment. An Inuit may have dozens of descriptive terms for types of snow, whereas a Yanomamo would know 30 different types of green. Typically, when there is contact between two disparate cultures, both languages assimilate new words and concepts quite rapidly — everything from the concept of numbers greater than nine to entire sets of new edible plants.

However, in the past century, language groups have begun to evolve new and shaded meanings for words that already had place and meaning.

There were some antecedents in the vocabulary I first learned for unpleasant things associated with sucking. One could be a sucker, get sucker-punched, and become suckered.

However, I remember when a stand-alone “suck” first began to acquire its new negative connotation. It was in my early college days and I tended to dislike its fall from grace, arguing there were in fact a great many instances in which sucking had a very positive connotation. Sucking on a lollipop or sucking milkshake through a straw were not only pleasurable but demonstrated a quite amazing ability shared by most mammals and even some birds.

Sucking is basically the conscious reproduction of peristalsis, the amazing alternate constriction and relaxation of muscle groups which moves materials throughout the body. To think that creatures would be born with this concept, translated into all sorts of different shapes and sizes, is just mind-boggling. A suckling infant uses the same basic techniques whether it is a human baby or an elephant with a big trunk in the way or a blue whale with a hugely elongated jaw doing it underwater while swimming. To have this seamlessly interact with the direct peristalsis of swallowing is a truly wonderful characteristic.

We tend to think of non-mammalian processes as similar, but in most cases they are not. This is especially true in the case of insects. For example, we talk about ticks and mosquitoes sucking our blood. In fact, the mechanism for most penetrating parasites like this is simply to tap into a blood vessel, which has positive internal pressure, and let the host’s heartbeat and blood essentially push the fluid into the insect’s stomach.

Some others, feeding on less pressurized fluids, use simple vacuum pressure, expanding their abdomen to pull fluids into their digestive systems. A spider feeding on the liquefied internal structures of a captured fly uses this technique.

Recently anatomists have discovered another biomechanical process used by some insect families, which is truly amazing in not only its process but by in the astonishing pressures involved.

Most insects that feed on plant sap tend to go for the phloem — the plumbing system that moves sugar- and nutrient-rich material from where it is produced by the leaves to the rest of the plant.

There are, however, a few hardy species that focus on the xylem — the tubular system that brings water and dissolved minerals up from the roots. Material carried in the xylem is not only very low in nutrition by volume, but the mechanism for moving it involves some extreme negative pressures within the tubes. When an insect penetrates a xylem tube there is no oozing, but rather a reaction much like sticking the floor vacuum’s hose to your sibling’s back (I never did that but I have heard of it happening).

One family of xylem-feeders you may be familiar with in this area are commonly known as “spittle bugs.” These insects are typically noticed by a large wad of bubbles on the stem of a plant. This is often described as some sort of camouflage mechanism for the insect inside, but there is a simpler explanation.

The spittle bugs are more correctly called froghoppers, named for their tremendous leaping ability. To feed, they probe with a beak and penetrate a xylem tube. In this tube, they encounter a negative pressure of over 1 megapascal. It is not necessary to go into how this measurement is derived, but to overcome 1 megapascal takes pressures roughly equivalent to a human sucking water out of a glass that is 20 feet below them, through a straw that is 100 yards long.

To generate this incredible pressure, froghoppers do not suck. Using micro CT scans, researchers determined they have inside their head a structure that looks and works very much like a piston, and with this they create pressure in much the same manner many water pumps operate. This system is very efficient and, once it overcomes the negative pressure, it can move large amounts of liquid. This is important because the xylem fluids are so nutrient-poor that it takes a lot to nourish a single froghopper.

This is where the spittle comes in. The froghopper must eliminate a lot of water along with the gases produced by digestion in order to maintain a throughput sufficient to nourish the insect. They are excreting tremendous amounts of water along with the digestive wastes.

If you were functioning like a froghopper, you would be continuously urinating over three gallons every minute and piping methane through it to make bubbles.

Spittlebugs are amazing animals and they definitely do not suck — they draw…

Bob Henke writes a weekly outdoors column for The Post-Star.


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