Eat the Beetles!: An Exploration into Our Conflicted Relationship with Insects

by David Waltner-Toews

  Termites are also an example of how insects evolved intimate relationships with the microbial world. Many people think that because termites eat wood, they can also, somehow, digest it. This is only partly true, and only for some types of termites. Termite guts are home to communities of bacteria, archaea, and, in some cases (in the case of what are known as “lower termites”), flagellated protozoans. These microorganisms depend on each other, in an arrangement called obligate symbiosis, to break down and digest lignocellulose, an important component of woody plant cell walls. Lignocellulose decomposes very slowly and is not very digestible by most animals.46 In addition to termite microbiomes with protozoa and protozoa-associated bacteria being able to break down lignocellulose to access carbon, the termites need to get access to nitrogen in order to build amino acids and proteins. Some of this is accomplished through internal recycling, and some through a social behavior called proctodeal trophallaxis. This behavior, which involves seeking out and sipping droplets of hindgut fluids from nestmates (try not to think about it), can be traced back to the common, ancient ancestors of termites and wood-eating cockroaches.

  About sixty million years ago, some termites (called higher termites by those who are on more familiar speaking terms with them than I am) lost their resident protozoa and were forced to get creative in how they managed their food supplies. Some of their descendants took up farming: Termitomyces, or the “termite mushroom,” is so named because it grows only from termite nests, which can break down lignocellulose. According to a 2001 research report, so-called “old workers” forage for plant litter outside the termite nest. “Young workers” inside the nest chew up and swallow the plant material, but don’t digest it before excreting it. They then take the fecal pellets and press them into a sponge-like “comb,” which serves as a garden bed for the fungus to grow. As the fungus matures, its lignin content decreases, making the material more digestible. Young termite workers eat the fresh nodules while older workers eat the older mushrooms (which are more digestible). Sort of like young people eating indigestible granola for breakfast, and old folks getting fed porridge. Thus, termites are farming fungi, and in the process are making proteins and fats that are excellent foods for people and other animals.

  Not all relationships between insects, bacteria, and fungi are so congenial. One might think about Ophiocordyceps unilateralis, the fungus that provides the premise for M.R. Carey’s remarkable 2014 novel The Girl with All the Gifts. That zombie fungus, as some call it, invades the nervous system of ants in the Campomotini tribe, causing them to climb down from their canopy homes, settle on the underside of leaves, and then explode in a puff of spores. Or Dicroceolium dendriticum, the sheep liver fluke parasite, whose life cycle takes it from sheep dung to snails, and from snail slime to ants, where it takes over the brain. The ants climb up the grass, waiting for sheep to eat them to complete the cycle.

  Moving up a scalar notch from insect–mineral and insect–microbe relationships, we encounter insect intrigues and betrayals worthy of a Shakespearean treatment.

  Sometime during the Jurassic period, some wood wasps decided to give up their vegetarian diet and eat beetle larvae. Over the years, these carnivorous insects evolved and diversified from a few species to hundreds, to thousands, to hundreds of thousands. Rather than heading out into the woods and shooting down whatever they could get, these wasps, called parasitoids, developed a novel, more finessed, approach. Some of them, like the tiny fairyflies I introduced when we were puzzling over the millions and millions, inject their eggs into the eggs of other insects. Others, like the Tachinid fly family members (which are Diptera, or true flies) put their eggs just behind the head of a caterpillar, so when the eggs hatch, the larvae can eat their way into the living dinner. In some cases, a parasitoid wasp finds a young beetle larva inside a plant and injects a paralyzing, but nonlethal, venom into it. She then lays her egg next to the paralyzed larva. When the wasp baby hatches, it eats its way into the freshly preserved flesh. In a variation of this, some parasitoids insert their eggs directly into the insect that they want to parasitize; in this case, disabling the host’s immune system is a challenge. Somewhere along the evolutionary way, a virus “decided” to hitch a ride with the egg, disabling the host’s immune system to the benefit of both virus and parasitoid.

  Some wasps have developed a cluster of cells called a trophamnion (a peculiar insect version of a placenta), which protects the wasp egg from the host’s immune system and provides nutrition to the developing baby by absorbing nutrients from the host’s blood. When the egg hatches — still inside the living insect host — it becomes what is essentially the tiniest aquatic insect, molting, floating around, sucking in food (but not defecating), and finally eating its way out into the outside world. By that point, of course, the host has been killed by the parasite. If the host is paralyzed, both the host and the parasite are stuck in one place. This works for the parasite as long as the host doesn’t get eaten by some larger animal, such as a bird, or die for other reasons. In that case, both the host and its parasite are out of luck.

  In the late Jurassic, another variation, called koinobiosis, emerged among the parasitoids; in this case the host, with the parasite inside, lives on and even goes through several molts before dying. In some cases, parasites of the parasites have emerged. In at least one case, a wasp that parasitizes the larvae of cecropia moths is itself parasitized by a smaller type of wasp, which may also be parasitized by an even smaller one — and, in the spirit of Jonathan Swift, that one is occasionally parasitized as well. These parasitoids are, in ecological terms, ingenious and diverse pathways for keeping various plant-eating and insect-eating populations in check, and they have been used for nonchemical pest control. They are doing us a favor then, so that we aren’t overwhelmed by the bigger wasps and yellow jackets. They have also created wrenching problems for some scientists trying to imagine what sort of a god would have created such suffering — if one can call it that. Darwin’s reluctant atheism (if indeed it was atheism) can be blamed on these creatures.

  An important lesson for insect-eaters to take away from inter-insect relationships is that, in the wild, they keep each other’s populations under control. Disturbing these relationships through the direct or unintended collateral damage of foraging and farming some of them may result in population explosions of others, shifting their status from minor irritants to major pests.

  Beyond insect–soil, insect–microbe, and insect–insect relationships is the more familiar insect–plant buddy system.

  In some cases, insects, like humans, will use plants for their own ends with no obvious advantage to the individual plants, but ultimately for what we might, in retrospect, characterize as the common good. In North America, for instance, about 1,700 insect species — mostly midges, flies, and wasps — are gall makers, commandeering plants’ hormonal systems to create tumor-like growths, known as “galls,” to provide homes and food for themselves. What’s galling to the plants is that it decreases their seed production because it redirects their resources. The affected plants have obviously adapted; perhaps the galls limit plant growth and reproduction in such a way that they don’t overpopulate and destroy their environments.

  Mopane worms, the larvae of emperor moths (Gonimbrasia belina), are today considered a culinary delicacy in that cradle of human origins, southern Africa. What were they doing before our pre-human ancestors met them and invited them over for dinner? The mopane trees on which the larvae feed grow in woodlands across several southern African countries (Botswana, Zimbabwe, Namibia, northern South Africa). Elephants are the only other animals to eat a significant amount of mopane foliage; with their demise and retreat into parks, the caterpillars are a last defence against the slow, persistent march of dense, impassable, relatively infertile mopane-dominated veld across the landscape. Even where elephants are present, the caterpillars, which increase their body mass four thousand times during their six weeks of larval life, consum
e ten times more mopane than the elephants and drop almost four times more soil-enriching dung. In a word (okay, a few words), these larvae created, and still maintain, some of the most memorable and habitable landscapes in humanity’s birthplace. Well, habitable for people and other charismatic megafauna, at least.

  Palm weevil larvae are another group of bugs entering haute cuisine kitchens in the twenty-first century. Again, we would do well to understand the important work they were doing well before being discovered by previously non-insect-eating adventurers. Stressed, severely wounded, or dying palm trees speak to palm weevils (Rhynchophorus ferrugineus) in the language of volatile compounds (the arboreal version of perfume). The male beetles fly toward the source of the perfume, land on the suffering tree, and release their own pheromone messages to other males and females. The enticing chorus of tree and beetle perfumes brings more beetles, who then mate and lay eggs. The larvae, with sharp beak-like “noses,” burrow into the palms and break down the wood; this is bad for the individual tree, but good for both the weevil and the ecosystem. Not only that, but because the weevil larvae are making nutrients available to trillions of other insects, fungi, and bacteria, and enriching the fragile tropical understory, they are providing a service to the forest of newborn baby trees. It was not until after postindustrial humans arrived and created plantations of date, oil, and coconut palms that the weevils were seen as pests. But is it their fault that we were not biologically mindful?

  Orthoptera (grasshoppers, crickets, and locusts) are part of that web of herbivores that helped, and continue to help, recycle nutrients and determine the diverse, mosaic landscapes of natural systems that support other plants and other animals. They were doing excellent ecological work well before we reclassified them as plagues, protein, and, if you are poet Mary Oliver, beings to ponder and be amazed by, as in her most wonderful poem, “A Summer Day.”

  Like many Just Plain Folks, I tend to mix up grasshoppers and locusts, especially when they are on my plate. This is not surprising, I suppose, given how closely related the two are. However, locusts may provide only opportunistic disaster food relief whereas grasshoppers can become a staple, so we would do well to differentiate between them. In brief, all locusts are grasshoppers, but not all grasshoppers are locusts. Locusts are the ones that darken the heavens with their terrifying swarms; the shift from the solitary phase to the swarming phase is called phase polyphenism by the people who study orthopterans. If, like me, you prefer plain English, the locust transformation is a kind of Dr. Jekyll and Mr. Hyde story, or maybe an insect version of The Incredible Hulk, in which a regular, hard-working Joe is transformed into an uncontrollable, life-threatening beast. Of the more than ten thousand grasshopper species in the world, only about a dozen are classified as locusts. I’ll talk more about locusts later, when I talk about pests, but for now, let’s focus on the normal, Joe-Blow lives of grasshoppers.

  In general, nonswarming grasshoppers are pretty much herbivores, eating a wide variety of plant species in a wide variety of rangeland and grassland habitats. In the past few decades, trying to get beyond the napalm/scattershot/neurotoxin–bombing approach to controlling them, researchers have looked more carefully at what these creatures actually do. Are they are always the villains we take them to be? Or are they a misunderstood spiritual totem? As one might have expected given nature’s diversity, the answer is: both. Or, better yet: it depends.

  Some grasshoppers, in some landscapes, eat plant species that, on their own, have slowly decomposing litter. This grasshopper feeding activity encourages plants that decompose more quickly, and this, in turn, speeds up nitrogen cycling and increases overall plant growth. Other grasshoppers, in other landscapes, prefer different plants and may suppress overall production.

  Crickets too are rapidly becoming a staple of the entomophagy movement. Also belonging to the order Orthoptera, they are closely related to grasshoppers, locusts, and katydids. Like most of their relatives, they have taken to heart author Michael Pollan’s widely advertised advice to “Eat real food. Mostly plants. Not too much.”47 Among the two thousand or so cricket species in the world, most are herbivores who occasionally backslide into omnivorism. Like their grasshopper relatives in the wild, crickets are dedicated and diligent members of decomposer and nutrient-cycling communities, those unsung (but, in the case of crickets, singing) heroes of life on earth. They contribute by devouring huge amounts of cellulose-rich plant materials and producing frass (the technical name for insect waste products) that makes the energy and nutrients inherent in the plants available to bacteria, fungi, and, ultimately, to us.

  Yellow mealworms, another entomophagical delicacy, are larval forms of Tenebrio molitor (darkling beetles), and members of a twenty thousand-species family — a family with dark secrets, judging from its Latin name, the Tenebrionidae. Some of us of a certain age are familiar with these animals as squiggly things in our mothers’ flour bins. My mother sifted them out. Other mothers (perhaps Daniella Martin’s?) may have fried them up and whisked them into an omelette. Other members of the same family are known as pests in grain-storage facilities and chicken barns, or as food for pet reptiles. Like other insects, different members of the darkling family have different jobs besides helping and pestering us. Various species within the family feed on such delights as decaying leaves, rotting wood, dead insects, dung, and fungi. In other words, they are more important and diligent recyclers than even the most obsessive blue box and green bin advocates. Furthermore, as part of the no-free-lunch ecological society, the great circle of life, and several other community-service clubs, they are themselves food for birds, small rodents, and reptiles, both in the wild and, more recently, those kept as pets.

  Insects also played essential, nurturing roles in making sure the angiosperms —flowering plants — of the Cretaceous (100 million years ago), were properly cared for after the messy and violent divorce and fragmentation of the great Pangaea supercontinent (which started about 200 million years ago). It is in the relationships between insect pollinators and flowering plants that we go beyond technical relationships and begin to understand just a little better the languages of conversation among insects and plants. In their roles as pollinators, insects and plants have evolved exquisitely intimate relationships.

  The cacao tree (Theobroma cacao), a.k.a. the “food of the gods,” originated millions of years ago in what is today Central and South America, although humans only began to make bitter chocolate beverages around 1900 BCE. One version of the story has it that the Aztec god Quetzalcoatl shared the secret of chocolate with humans, a transgression for which he was thrown out by the other gods. If one is inclined to make moral judgments, one might concede the rightness of their actions; apparently removing cacao beans from the pod is like removing a human heart during a sacrifice. Today cacao is grown in Africa and Asia as well as in the Americas, providing the cacao beans around which a US$50-billion industry is constructed. The tiny, white, downward-facing Theobroma flowers — which open at dawn and only last a day — grow directly off the lower branches of this tropical rainforest tree. The wild cacao flowers give off a complex perfume of more than seventy-five distinct aromas, which attract tiny midges of the families Ceratopogonidae and Cecidomyiidae — the only insects that can pollinate them. The midges, which do not travel far from home, require specific microhabitats in shady rainforests. In light of this information, growing Theobroma on small farms in the midst of rainforests, and protecting midge habitats, would seem to be a more intelligent strategy than clearing the forests for poorly producing plantations. This may seem unfair to the monocultural industrial cacao plantation owners, but then, I don’t suppose the midges and flowers were thinking about treating corporations fairly when they eloped to the rainforest.

  Fig trees offer an important illustration of how sustainable food systems, cultural identity, and economic class-based biases interact. These trees are important food sources for fruit bats, capuchin monkeys, langu
rs, mangabeys, Asian barbets, pigeons, bulbuls, and fig parrots, as well as the caterpillars of crow butterflies, plain tigers, giant swallowtails, brown awls, green garden loopers, and metalmark and “tropical fruitworm” moths. Fig trees also have symbolic importance in Hinduism, Islam, Jainism, and Buddhism (Buddha having found enlightenment while sitting under a fig tree). And remember Adam and Eve and the fig leaves? So, it makes sense that fig trees were a symbol of fertility in ancient Cyprus.

  With a few exceptions, each of the thousand or so species of fig tree is (mostly) pollinated by its own companion wasp species. Not only that, but the female and male parts of the fig flower mature at different times. The wasp larvae grow inside the fig ovaries; the male wasp hatches and breaks into his sister’s “bedroom,” mates, and then (in remorse and anguish?) commits suicide. The now-pregnant female heads out, picking up pollen from the male parts of the flower, and flies to another fig tree where, pushing her way past the scales at the door, she pollinates the female parts of the next tree.

  But not all figs and flowers are alike. In the 1880s, Californians imported Smyrna figs, which were known to produce delicious fruit. What the Americans did not realize was that Smyrna figs needed pollen from hermaphroditic caprifigs, which are apparently only good for goat food (a pretty low bar). Because of the way that Smyrna fig flowers are structured, fig wasps cannot reach in far enough to lay their eggs. The wasps lay their eggs in the caprifigs, where the young overwinter. In the spring, they fly out and pollinate nearby fig flowers, including those of the Smyrna figs, where they attempt, unsuccessfully, to lay their eggs. So the wasps need the caprifigs and the Smyrna figs need the wasps. In the 1880s, when American botanists first heard this story from European fig growers, who told them they needed to import both wasps and caprifigs in order to be able to produce figs for human consumption, they laughed. LOL! Old men’s tales! Idiot farmer hicks! By the early twentieth century, still unable to get their fig trees to deliver the goods, they started importing.