Scale Insects, Spittle Bugs and Other Lovelies
by Richard L. Howey, Wyoming, USA
As anyone who has a yard and/or houseplants knows, one must be prepared, at a moment’s notice, to do battle with hosts of invaders that have evolved an enormous box of tricks in order to feed on your prize botanicals and defeat your pathetic, human attempts at counter-warfare. We have been led to develop an arsenal of chemical insecticides and systemic poisons and, in desperation, are now trying to figure out the mechanisms that nature itself has developed by means of which plants protect themselves from pests. In other words, many pests have been versatile enough to find ways around our paltry chemical assaults and so we now seek to understand a manifold of biological controls that have been evolving for millions of years.
However, for opportunistic microscopists such as myself, what most people regard as mere nuisances, can be transformed into fascinating and puzzling objects of study. In our dining room window, I have a tall spindly specimen of False Aralia (Dizygothea elegantissima) which, as it turns out, is infested with Brown Scale Insect (Kilifia sp.). For those of you who have not had the pleasure of making its acquaintance, it is, I assure you, bizarre enough to have come from some planet circling Betelgeuse. It looks rather like a brown scab; it is flattened and ovoid and it has rather small weak legs relative to its size when an adult. Its mouth parts bore into the leaf vein, or stem to feed on the sap and they must be quite sharp to penetrate the tough layers of the stem or the rather resilient epidermis of the leaves. These insects are feeding and breeding machines. They excrete what appears to be a sort of sticky, clear resin that sometimes forms sizeable globules. In some instances, after sitting a while, part or all of the globule will turn an opaque, milky white. Sitting in the window next to and sort of entangled in the False Aralia is a metal and stained glass sculpture which I bought my wife many years ago as an anniversary present. In the image below, you can see how these resinous globules have formed what appears to be a network very much like a web.
However, it’s impossible to imagine these scale insects spinning out lines and globules and swinging from leaf to leaf, as I think you will agree, when you see how they more or less glue themselves to the surface of a leaf or stem.
Once an adult female settles in, she almost always remains in that spot and begins to produce eggs. The males are apparently very small and can fly, but I have not yet been able to locate any. The female produces eggs under the protective cover of her tent-like body and they hatch while still under her body. When they are hatching, there are odd triangular bits of white fluff all around the hatchlings which begin to crawl out from beneath their mothers to find a place of their own to feed. These “crawlers” rarely go any significant distance from their mothers, but they do appear to go through at least 2 stages before settling to feed. Here are 2 images of the hatchlings.
You will notice that they have not yet developed the posterior “feelers” that are to be seen in a larger, and presumably later, stage of development.
As you can see in this stained specimen, they do have primitive eyes which are probably only useful for orientation to light intensity. In the fully developed female, that is, one which is producing eggs, the legs seem very spindly in relation to her overall size and I suspect that at this stage, she is no longer really capable of movement of any distance, if at all. She also possesses a pair of dorsal appendages.
I wonder if their feeding stimulates the plant to increase its production of sap.
I trimmed off all the lower branches of the plant, as they were heavily infested, and after examining and photographing a fair sample of specimens, I took parts of leaves and stems that were most heavily populated and preserved them in 70 % alcohol. After I examine these, I may have a few more comments about their morphology.
For several summers I have noticed on the juniper bushes along the walkway up to our house that spots of white foam about the size of a dime appear on many of the branches. So, last summer I finally got around to investigating. I knew it was some kind of insect but, since they never did much damage to the junipers, I had ignored them. I cut small bits of branch into a plastic dish, so that I could leave the foam environment as undisturbed as possible. In my lab, I transferred one of the pieces into a small Petri dish and carefully began to scrape away at the foam to see what lay beneath—and “what to my wondering eyes should appear...”, well, I assure you it wasn’t St. Nick and 8 tiny reindeer. This thing looked like a baby out of the movie Alien.
It is, of course, a spittle bug and aptly named, except in this case, the spittle is generated at the other end. It is almost amusing to watch its thorax pumping away, producing bubble after bubble that forms its protective housing.
In the next image, you can see the long, needle-like feeding tube which it inserts into the juniper in order to feed on the sap.
Observing these creatures while they are still living and active is fascinatingly repellent at first, but after a short time, these bizarre organisms are simply fascinating. Nature, after all, has no concern for our aesthetic sensibilities, so you have to have a set of tough sensibilities to be a naturalist or be very good at sophistic self-deception, seeing only the beautiful and positive side of the physical and biological processes and creatures that constitute nature. Nonetheless, there are indeed some organisms that overwhelm my attempts and remain deeply repulsive, but that’s a topic for another essay.
For my wife, the most detested plant pest is the mealy bug. At the bottom of our stairwell, by a South window, we have a medium-sized Ficus , a rather unusual fig plant given to my wife by her brother. When she repotted it last year, she took it out to the garage and used some old potting soil. She is convinced that this is how it acquired the mealy bugs. Since then, we have sprayed it with soap solutions, alcohol, and most recently I have taken to using alcohol wipes on the leaves and cotton swabs soaked with alcohol to kill the ones on stems. At last we seem to be making some progress. However, naturally, I took a heavily infested leaf, which was about to drop off anyway, put it in a Petri dish, and transported it to my lab for examination. You will notice that the “crawlers” have a distinct similarity to those of the scale insect.
The mealy bug “crawlers” seem to be more active and travel further from the mother. With these types of sap-sucking insects, it seems to be the case that the adult female is the one that inflicts the most damage and becomes sedentary, fixing the mouth parts more or less permanently in the plant. With scale insects and mealy bugs, it is difficult to remove them alive with the mouth parts intact. The adult female mealy bug has a “cottony” appearance over its light pinkish body. When I suggested to my wife that they looked rather like miniature balls of cotton candy, I received one of her searing looks of utmost disgust.
These three are not the only plant nuisances in the house. I had a nice little broadleaf plant in my lab window–unfortunately I have now forgotten what it was–and it seemed to be doing well, but then a leaf or two started ailing. I turned over a few leaves and immediately got a plastic bag and pitched the plant, pot, and plastic saucer into the garbage. The undersides of the leaves were almost solidly covered with whitefly. Belatedly, I realized that I hadn’t even pickled any to study.
The houseplant pest which wins my award for the biggest nuisance is the spider mite. These creatures seem virtually unstoppable–sort of the army ants of the semi-micro plant pests. Short of using a flame thrower, they evade or adapt to everything I throw at them. I have gotten to the point now where, if I discover a plant with spider mite, it suffers immediate eviction.
If you move to the outside world, then the number of plant pests increases exponentially–pine beetles, leaf rollers, cabbage moths, big, fat hideous green tomato worms, cut worms, and on and on–but that’s a whole other story.
Since, I first wrote this, I have found out a few additional bits of information which I wish to add here. Last year, one of our large spruce trees died–I think from a combination of spider mite, bark beetle and fungus. A second one looked rather sickly this spring, so we had it and 5 other spruce sprayed with nasty Malathion , an organophosphate which is a nerve gas analog. A few weeks ago, I noticed on 3 of the trees, white spots on many of the needles, so I called the lawn service people and had the trees sprayed again. Two weeks later, still lots of little white lumpy spots. I snipped off some samples and took them up to my lab. As I suspected, another infernal scale insect–pine needle scale. The adult female is especially pernicious. Her head and thorax are short, her mouth parts are embedded in the pine needle and she apparently feeds more or less constantly.
She secretes a white cottony fluff which covers her body and wings. The wings are quite long in relation to the body and protect the eggs. Over all she is only about 1/8 of an inch long, but she is a veritable egg factory. I took one specimen and pried her loose from the pine needle and there under the wings was one crawler which had just hatched and 120 eggs! We are now having the lawn service pump a systemic insecticide into the ground around the trees.
Significant areas of forest in Wyoming and Colorado are at present being attacked by bark beetles, as well, which can kill large stands of trees. In part, this infestation is a consequence of drought, in part, global warming, and in part, a result of forest mismanagement. In any case, we are trying to save our six remaining old spruce.
Earlier when I was discussing the False Aralia I had sitting in the dining room window, I mentioned some weblike structures around a piece of glass sculpture. (See image above.) The plant continued to produce new top growth and flourished alongside a small bamboo palm and two Tradescantias. Unfortunately, as the False Aralia continued to flourish, more and more of the sticky sap got deposited on the window until my wife issued an ultimatum. For some odd reason, she thinks windows are for looking out of onto the outside world. Now, this is a fairly large window, being 5 foot by 5 foot but, nonetheless, I was confident that half an hour would see everything right. One of the first rules of household chores is to take your estimate and multiply it by 10. There is no such thing as a simple household task! Every domestic enterprise can teach you a fundamental law of the universe: Everything is endlessly interconnected. The “simple” task of cleaning this one window involved restructuring the cosmos. Well, O.K., that’s a slight exaggeration, but it did involve reorganizing the dining room–I’ll spare you the tedious details. All of this is a long-winded way of telling you that I found out that all of the plants–the False Aralia, the bamboo palm, and the 2 Tradescantias–were infected with a variety of minute critters and I ended up (with strong encouragement from my wife) throwing all of them in the garbage. There were in addition to the scale insects, some tiny mites, some small gnats which laid eggs which hatched into small maggots before turning into more gnats, and a group of wee spiders–in other words, a veritable insectarium in our dining room area. At last, an explanation for the webs around the glass sculpture and the tiny resinous globules on the strands! Or is it? How do the spiders keep from getting stuck in the resin? Now, I’ll never get to investigate and find out. Spiders have evolved ingenious mechanisms for adapting to extraordinary circumstances, so perhaps it’s no surprise that there is a species that can make webs using resinous sap.
My wife and I certainly aren’t compulsively neat people, but neither are we slovenly, so the plants and the insects had to go. I don’t like having loose insects in the house, but I’m still curious about those webs.
One final observation. We have lots of lilac bushes in our yard and every year, as autumn approaches, many leaves get seriously notched.
I wonder what sort of Vegan insect could chomp all these neat little geometric notches–perhaps a Euclidean leaf cutter ant. Then, somewhere from the dark and mysterious recesses of memory, I recalled a mention of lacewings (a.k.a., green flies) munching in such a fashion. It still seems a puzzle to me. When on these autumn evenings, I sit on our tiny side porch, I do see lacewings and admire their lovely green translucence, but I have a hard time believing that they are the culprits of such geometric mayhem on such a gargantuan scale. Perhaps next autumn, when things are a bit less hectic, I shall find time to pursue this small puzzle.
In the meantime, I proffer this bit of advice regarding your houseplants: Be ever vigilant–our Ficus has mealy bugs again!
All comments to the author Richard Howey are welcomed.
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