I remember feeling a unique joy anytime I encountered spittlebugs as a kid. These are the teeny insects that leave surprise wet spots on your shins as you walk through tall grass. Sap-suckers like spittlebugs are everywhere, but most are much more inconspicuous. There are tens of thousands of species of insects all over the globe exploiting the nutritious liquid inside plant stems, leaves, and roots. The following are just a few of the local sap-sucking phenomena that we’re lucky enough to witness in the spring and summer in Maine.
Those spittlebugs that kids plow through while running free in a field are actually nymphs—baby spittlebugs. In this early, vulnerable stage, they create bubbles using excess sap secretions, air, and a special substance that increases surface viscosity and makes the bubbles last longer. In essence, they are miniature bubble machines, bubble solution and all. As air is forced from their abdomen, creating bubbles, the little insects reach behind them with their back legs and pull the foam over themselves. At a rate of up to eighty bubbles per minute, they cloak themselves in a foamy home that protects them from predators and desiccation. It’s perhaps worth mentioning (or perhaps not) that this is all a function of the spittlebug’s anus, so it’s not technically spittle. Do with that information what you will. There are over thirty species of spittlebug in North America; one of the most common in Maine is the Meadow Spittlebug. Nymphs are bright green, perfectly camouflaged with tender leaves and stems; adults are mottled brown and about five centimeters long with legs folded under their bodies, ready to hop at any moment.
Spittlebugs are only the foamy tip of the iceberg. Just under the leaves and along the stems of plants, aphids roam. Aphids in particular provoke the ire of gardeners and farmers. There’s one type of farmer, however, that absolutely loves aphids. Many species of ants reckon themselves certified aphid ranchers. Aphids, like spittlebugs and other sap-sucking insects, bite into the phloem of plants, which carries nutrients and sugars created in the leaves through photosynthesis down to the roots. The phloem are pressurized, so when the insects tap into it with their specialized mouthparts, the sap shoots through them. It quickly passes through a gut which both filters it for crucial nutrients like nitrogen and creates the amino acids that aren’t naturally present in the sap. The latter is accomplished by special bacteria that live inside the cells of the insect, unlike our own digestive bacteria, which only float around in our organs. Perhaps we should be calling them “the biological collective formerly known as ‘aphid.’”
So where do the ants come in? Because sap is fairly low in other nutrients, aphids have to drink a lot of it, and the excess water and sugar leaves the bug almost as quickly as it entered. Unlike spittlebugs, aphids don’t make direct use of the secretion, known as “honeydew,” but ants consider it a tasty source of calories. Known for being drawn to sugar, ants go bananas for honeydew. They love it so much, they’ve evolved ways to keep the aphids close. Many species of ants lay down a chemical trail with their feet that both sedates the aphids, keeping them together in one place, and increases their reproductive rate. They’ll herd the aphids to “greener pastures” and to their nests in the soil at night to protect them from predators. The predator-protection piece is what’s in it for the aphids. Aphids are a tasty meal for many flies, lacewings, and beetles. When aphids grow their wings, ants sometimes clip them so they can’t fly away. And yes, they do occasionally eat aphids to keep populations a convenient size or when they need extra protein. Ant cannot live on sugar water alone! Despite this risk, the relationship is a net gain for the aphids. Aphid husbandry, (officially known as ant-aphid mutualism), has likely evolved multiple times, one of many fascinating examples of convergent evolution. Around a quarter of the 4,000-or-so species of aphids are farmed by ants.
Last, but most certainly not least, are the leafhoppers. These are the epicurean’s spittlebug. They come in an outstanding variety of colors and patterns, they produce songs like cicadas, and they don’t blow bubbles from their rear ends. Leafhoppers also have piercing-sucking mouthparts, and tap into the phloem of plants. They’re not as infamous for damaging plants as aphids, but certain species cause problems in some areas. In Maine, Potato Leafhoppers can damage beans, potatoes, eggplants, strawberries, alfalfa, and hops… that is, if they can get up here. Potato Leafhoppers spend the winter on the Gulf Coast and migrate north in the spring. They have wings, but wind currents give them an extra boost. Some years, very few of these three-millimeter-long insects make it as far north as Maine; other years, farmers are plagued by them.
Other species are less voracious or fecund, but can be vectors for plant pathogens. This includes one of the prettiest insects I’ve ever seen, the Red-banded Leafhopper (pictured above). This species thankfully isn’t considered a major pest in Maine, so we can fully appreciate their Superman colors. They love Rhododendrons, Laurel and Mountain Laurel, Roses, and Forsythia, but I’ve found them on all sorts of plants.
Leafhopper “songs” are faint and not made to be transmitted through the air, like those of cicadas, but rather through the leaves of plants. Vibrations are produced by an organ called a tymbal, located on the underside of a leafhopper’s abdomen. The tymbal’s surface looks like it’s made from one of those plastic corrugated noise-maker toys that can expand and contract. Sound is made when muscles contract and fold the surface in on itself one ridge at a time. The clicks are the “pop” of each of those ridges being buckled, one by one, extremely quickly! Leafhoppers find mates by sending these vibrations through leaves to others on the plant, and they sense their neighbor’s vibrations with specialized organs in their legs. Leafhoppers are little guys, and using vibrations to find each other is a lot more efficient than searching under every leaf for a mate.
Spittlebugs, aphids, and leafhoppers are in the order Hemiptera, which are the “true bugs,” and also include planthoppers, assassin bugs, shieldbugs, cicadas and more. All have piercing-sucking mouthparts, and some, like bedbugs, are animal parasites. All are important food for larger insects like spiders and wasps, as well as birds. The next time you encounter a foam-covered nymph, a herd of aphids, or a striking leafhopper, I hope you take some time to appreciate the unbelievable adaptations that have allowed these animals to flourish practically everywhere that there are vascular plants. At the very least, I hope you’re grateful that they’re herbivores!
