Dr. Michael Wall, BHP Guest Expert
Curator of Entomology, San Diego Museum of Natural History
Note from BHP Team: Bugs: the tiniest of creatures, with a big impact on history. Curator of Entomology Michael Wall, from the San Diego Natural History Museum, covers the history of insects in this month’s Big Question content update. From gracing the menus of our earliest ancestors, to impacting major geo-political events, there are some surprising intersections in the stories of insects and humans. As we look to the future, we wonder how humans will continue to be affected by these six-legged creatures. Medical research and diet are only two facets of the vast frontier.
Curious to dig even deeper into this big topic? Michael will be conducting an Exchange in Yammer on January 23-25. He’ll share even more information about bug stuff, and then open the floor to questions. We hope you can join in!
If insects could talk, they might be tempted to say this to humans: “Insects rule the world now, and have for millions of years. Get over yourselves, bipedal mouth-breathers.” There is a lot of truth in that assertion. Parts of it are unequivocally verifiable. We are bipedal, and we are mouth-breathers, unlike insects. Where humans might get bent is with the assertion that “Insects rule the world now, and have for millions of years.” Let’s break it down and see where we land.
Insects have ruled the world for millions of years
Insects have been around for a long time. The first proven fossil of an insect crops up in the fossil record 407 million years ago. To put that into perspective, “living fossils” like the coelacanth first appear in the fossil record 380 million years ago, which predates the first dinosaurs by a cool 177 million years. Insects are the first animals to take flight—first by a long shot. Insects enjoyed complete aerial domination for over 170 million years, from around 400 million years ago until the first pterodons took flight about 230 million years ago. Some contend that one of the factors that drove dinosaurs and later bats to the skies, was the airborne food that insects represented. Speaking of catalysts of diversification, it is widely acknowledged that the love (pollinators) and hate (herbivores) relationship between plants and insects drove the diversification of flowering plants (angiosperms) in the Cretaceous. And it’s not even like those insects were some sort of freaky “prehistoric proto-insect” that had been long extinct. Almost all the “modern” lineages of insects predate the dinosaurs. So, they have been around for a long time, were the only flying game in town for millions of years, and have contributed to the evolution and diversification of birds, bats, and plants. They ruled then, but what about now?
Insects rule the world now
What does it mean to rule the world? Numerical dominance? Impact on history? Let’s tackle the numerical dominance, because insects have that in spades. There are over 1 million described species of insects on the planet, with an estimated 3 to 7 million that remain unknown to science—more than any other lineage on the tree of life. Ignoring the undescribed species, that means there are over 180 described species of insect for every species of mammal on the planet. In addition to the massive amount of species diversity, insects are numerically abundant in most terrestrial ecosystems and are important drivers of ecosystem processes. As you read this, there are at least 100,000,000,000,000 ants roaming the world. In other words, more than 13,000 ants for every person on the planet. And that’s just ants. In many places in the tropics, 10 percent of all animal biomass is termites alone, often exceeding 10,000 individuals per square mile.
All those numbers add up to a lot of ecological services for humans. They pollinate the plants that directly or indirectly make up much of the food on our tables. They are generally the first to begin the decomposition process for plants, poop, and dead animals. We would indeed be up to our eyeballs in “it,” if it were not for the decomposing prowess of insects. All those trillions of bodies are the biomass, the fuel, for the rest of most terrestrial and freshwater food chains, making insects vital to sport fishing and bird watching. One study estimated “the annual value of these ecological services provided in the United States to be at least $57 billion, an amount that justifies greater investment in the conservation of these services.” That puts insects at about #54 on the Fortune 500, just above Disney, which generates around $55 billion annually on a global basis.
Humans owe insects a lot of thanks, but insects at times have been one of humanity’s worst enemies, and have changed history on more than one occasion. Most notable was the death of 25 percent of the human population between 1346 and 1353, caused by the bubonic plague (the “Black Death”), which was transmitted via flea bites. Similarly, malaria, a debilitating disease caused by a parasite spread via mosquitoes, continues to kill between 500,000 and 750,000 people annually. At the pinnacle of the Napoleonic Wars, the French lost 95 percent of their 600,000 troops during the ill-fated invasion of Russia (1812 to 1813). While the causes of these deaths were many, typhus, a deadly disease spread by body lice, is estimated to have killed at least one-third of the troops, making it a major player in Napoleon’s ultimate retreat.
The Russians didn’t weaponize body lice to defeat Napoleon, but there are plenty of other examples of humans using “six-legged soldiers” in war. Honey from bees foraging on the Rhododendron shrub has been used more than once to disable invading armies. Rhododendron honey is also known as “mad honey” due to the toxins it contains, toxins that cause dizziness, weakness, and lack of coordination. Persians, who knew that honeybee hives were invariably plundered by advancing armies, placed “mad honey” along the path of the invading Roman army during the Third Mithridatic War. The Persian army waited for the symptoms to kick in, and then easily defeated more than 1,000 hallucinating and weakened Roman troops. In 946, Olga of Kiev used a similar tactic (and many other unsavory methods) to slaughter thousands of Drevlians as retribution for her husband’s death. The infamous medical officer of the Japanese army, Surgeon General Shirō Ishii, led efforts to aerially disperse plague-ridden fleas and flies covered in cholera from planes into China during World War II, which contributed to the death of around 440,000 Chinese.
However, insects are not all death and destruction, and have emerged as a possible goldmine for pharmacological research. New research is finding peptides from insects with antiviral, antibacterial, and antitumor properties. While we might hate mosquitoes and ticks, their saliva is loaded with anticoagulants and a host of other compounds being researched for medical use. Insects have long been used medicinally in non-Western cultures, but it has taken the emergence of antibacterial-resistant “superbugs” to get Westerners to overcome their entomological distaste and give ethnoentomology a fair shake. Then, there is maggot therapy. (Note to reader: Prepare your stomach before Googling “maggot therapy.”)
Insects will rule the world tomorrow
Humans have designated our current geological period the Anthropocene, a dubious honor related to humanity’s impact on the Earth’s ecosystems and climate. That’s fair enough. However, during their geologic tenure, insects have survived four different mass extinction events that snuffed the life out of other major lineages. My money is on them surviving the current mass extinction event and outlasting humanity. Someday, we will all realize that we are living in the Arthropocene—the Arthropod Scene.
About the author: Michael Wall, PhD., joined the San Diego Natural History Museum as Curator of Entomology in January 2006 and was subsequently named Director of the Biodiversity Research Center of the Californias. He also currently serves as Vice President of Science and Conservation. Dr. Wall is passionate about collections-based research and regional exploration. He is currently working to develop online resources that will increase public accessibility to the Museum’s rich biological collections.
Header image: Dogbane leaf beetle, by Alan Emery, CC0.
- Cordulagomphus sp. fossil, Brazil by Tortie tude, CC0
- Fossil insect from the Cretaceous of Brazil, by James St. John, CC BY 2.0.
- A 40- to 50-million-year-old cockroach in Baltic amber (Eocene), by Anders L. Damgaard, CC BY-SA 4.0.
- Ant in habitat, by Luke Elstad, CC BY 2.5.
- Formosan subterranean termite, by Scott Bauer, CC0.
- Plum dung beetle, by Charles J Sharp, CC BY-SA 4.0.
- The citizens of Toumai bury their dead during the Black Death. Miniature from manuscript, Belgium, 14th century, painting by Pierart dou Tielt (fl. 1340-1360), CC0.
- A female mosquito, Anopheles stephensi, obtaining a blood meal from a human host. By Jim Gathany, Centers for Disease Control and Prevention, CC0.
- A fruit fly, Drosophila melanogaster, feeding off a banana. The common fruit fly is one of the most widely used models organisms in biological research. By Sanjay Acharya, CC BY-SA 4.0.
- Hycleus lugens, a blister beetle, secretes cantharidin, which can be applied to treat warts and skin infections. By Muhammad Mahdi Karim, GFDL 1.2.