Insects That Spit

INSECTS THAT SPIT
 June 14 & June 16

It is spittlebugs that we are seeing right now. Or, at least, it’s the white froth trickling from plants that is getting our attention. The spittlebug is cleverly hidden inside this froth. One columnist friend of mine who was always quite graphic in his descriptions about such things,always referred to it in his columns as “phlegm.” You also may have heard it referred to as “cuckoo spit.”
Now that I have thoughtfully placed this graphic image in your mind, if you were to gently part the bubbles, you would see the insect responsible for this dollop of mucous. So, it is indeed an insect and not the plant that is excreting this fluid as some would think, although the plant plays an important role in its creation. But these are not adult spittlebugs, they are the immatures, or nymphs, and each one inside this frothy mass is happily chewing away on the plant. Adult spittlebugs, also known as froghoppers, feed on plants too, but are a bit more refined in their habits, and don’t drool all over the place, as do their kids.
So, what’s going on in there, and why the disgusting table manners when they eat? Well, there are different theories. We do know that it is the insect that is responsible for the foam, and we know it is excreted from the abdomen. Some think the bubbles result from excess air ingested by the insect during feeding, and others believe it is excreted for a reason – to protect it from being visible to predators since very few would be willing to probe this goopy stuff anyway – and others think it is a means of keeping the insect cool and moist. It could be for all those reasons.
How those bubbles are formed is another unanswered question. One theory says that the excreted fluid is mixed with air in a highly developed abdominal chamber into which a number of spiracles open. Others believe that the air is introduced not internally, but externally, as the fluid trickles down over the abdomen. Whatever way this foaming milky white substance is produced is uncertain, but it is an ingenious means of protecting the insect from harm.
Now here is the interesting part. Most insects that feed on sap, choose the phloem, the plant tissue responsible for moving food throughout the plant. These plant tissues contain what could be best described as sieve tubes to perform this function. However, spittlebugs feed on the xylem, the tissue that transports only water to the plant’s extremities – certainly not as rich in nutrients as the phloem. The spittlebug then, must get its sustenance from somewhere, and it does this by processing large quantities of sap to meet its needs, getting it almost entirely from amino acids. The more amino acids in the xylem, the better the survival rate of the spittlebugs. If you look closely, you will notice that spittlebugs are more prevalent in fields of hay – alfalfa, clovers – all legumes which are nitrogen fixers. These nitrogen-fixing plants with nitrogen-fixing bacteria are probably chosen by spittlebugs when they can find them, although you will find this little insect on just about any species of plant. On my morning walks up our road, I have found them on Queen Anne’s Lace, brome grass, and goldenrod, and even on a tiny sumac that was just coming through the ground.
The spittlebugs we are now seeing have overwintered as egg masses on some of the same plants on which they are now feeding. Even the egg masses are glued together with froth. Upon hatching in the spring, they appear as orange microscopic objects that move to humid sections of the plant and begins to feed and froth. During the course of their development, they will moult several times, changing colour as they go, eventually turning to green, whereupon they moult again, this time as an adult. Breaking out of this gooey mess, they continue to feed on plants, never really depending too much on flight. Mostly we see them hopping like frogs in front of us whenever we walk through a meadow of tall grass.
If the spittlebug in its nymph stage is interesting, the adult is even more so. At a mere 6 millimetres in length, the adult froghopper is almost able to literally “leap tall buildings,” Superman style, accelerating from the ground with a force that is 400 times greater than gravity. Compare that to the jump of a human which is only two to three times that of gravity. For a small insect, that’s a lot of g’s when you consider that humans can pass out after experiencing about 5 g’s. The secret is in the froghopper’s ability to catapult. Over 10 percent of the insect’s body mass is in its two leg muscles, and it’s these muscles that propel it.
Apparently, it does this simply by locking its rear legs in a closed position until the muscles store up enough energy to launch the insect into the air when occasion demands, at an incredible 4 metres per second. Absolutely amazing stuff when you consider that we likely learned how to use catapults a few thousand years ago, but these tiny insects evolved their own catapults inside their own bodies millions of years ago. And while humans might take several minutes to prepare a catapult and cock it into position, the froghopper can be ready in a millisecond.
So, don’t waste your time pursuing a froghopper on the premise you can catch one between leaps. It likely has more energy than any of us could hope to have. You’re far better off parting the froth on the plants and examining one of them in the nymph stage.