For the past few years I have made an effort to read during the summer. Thus far, most of my reading has focused on great naturalists of the 19th century, like Charles Darwin, Asa Gray, Alexander von Humbolt and others.
This summer I started with a biography of Louis Agassiz, an extraordinary scientist who was responsible for establishing the museum of comparative anatomy at Harvard University. Then I took a break from the past and focused on the present with a book by E.O. Wilson, who is another extraordinary Harvard professor. He made his mark on the world by studying insects — specifically, ants — and biodiversity.
Titled “Half Earth,” his book is simply outstanding. The third in a series, it looks at the ecological future of Earth and the possible consequences of inaction on the part of humanity. The book is clear, easy to read, accessible to the layman and, most importantly, it provokes serious thought and self-evaluation. Buy it and read it!
Agassiz was noted for his collection and classification of all sorts of animals, particularly fish. Asa Gray, also from Harvard, did for plants what Agassiz did for animals. Wilson followed in their footsteps, but he added a greater understanding of ecological relationships, building on the foundation laid by his Harvard predecessors.
Taken together, these works shine a bright light on the fact that Earth is simply brimming with life. We are but one of millions and millions of species alive now. More astounding, is the idea that these millions of species represent only 1 percent of the species that have ever lived — the other 99 percent are now extinct.
As you may remember from last week, I have been keeping lists of birds seen in my yard. I was talking about this with my beautiful wife Susan and my mother-in-law and they were both astounded that I could possibly know so many different birds.
That comment, combined with my current reading, got me to thinking. Here in North America there are 967 species of birds. I know many of them, but not all. Worldwide there are 9,956 bird species. I have a lot to learn.
Wilson studies insects — by far, the most numerous nonmicroscopic organisms on the planet.
Last year, I did a column on long-legged flies, and to do that column I needed reference books. I purchased a huge book on insects, in general, and another on flies, in particular. The fly book has 616 pages. On the first page of the introduction, the author suggests that we probably share the planet with 400,000 to 800,000 species of flies. Keeping those figures in mind, I continued.
All of this reading that I’ve been doing, combined with the possibility that I’m a little odd — that’s Susan’s opinion, not necessarily mine — produced a spontaneous experiment the other day. I had baked a pair of chickens, and in the process of preparing them, I pulled out hearts, gizzards and livers. Rather than throwing them away, I decided to save them for the crows. So I put them in a plastic tub and placed it in the refrigerator. So far, pretty standard stuff.
The spontaneity kicked in when I retrieved said organs the following day. Why not do a little experiment? Now, before I go any further, you have to swear to keep this a secret. Susan puts up with a lot, but if she knew the details of what I am about to tell you I might be in trouble. So you have to keep this to yourself, OK? If word gets out, by some careless comment here or there, I might be in for a serious scolding.
Rather than put the chicken organs out in the driveway, I decided to get a small pine board from the garage and place the organs out on the deck railing. This, I thought, would allow me to get good photos of some flies that I had started looking at last summer. I set up my camera, placed the bait on the west railing so the sun would be behind me, and I waited.
It took about 10 seconds for the first fly to show up, and within two minutes there was a veritable swarm. Snapping photos as quickly as possible, I was instantly amazed by the beauty of the flies and how that contrasted with the macabre scene in front of me. I recognized one species — the green bottle fly (Lucilia sericata) — right away. The others gave me trouble.
My efforts to identify those flies have resulted in a great deal of learning, but no real success. My fly book was only able to offer limited information, and this is understandable if we do a little math. Each page in the book is 8½ by 11 inches, which results in a surface area of 93½ square inches per page. Multiply by 616 pages and you get a total surface area of 57,596 square inches in the book. Divide that by the most conservative estimate of 400,000 species of flies and you end up with 0.144 square inches per species, or a square that is 0.38 inches on each side. This tiny box is not sufficient to print a species’ name, never mind show a photo.
In “Half Earth,” Wilson states that, “at least two-thirds of the species on Earth remain unknown and unnamed, and of the one-third known, fewer than one in a thousand have been subject to intensive biological research.”
I am sure that someone knows the exact identities of my mystery fly, but I am not that someone. The green bottle fly was easy. The other, I think, might be a blue bottle fly known as Calliphora vomitoria; a species that is surprisingly green for a blue bottle fly. Even if I’m wrong, I love that name.
Both species are members of the blow fly family (Calliphoridae), which has about 1,100 species that are known to science. Adult blowflies, characterized by their exquisite metallic blue and green bodies, are attracted to flowers, but their larvae specialize on carrion. This makes blowflies extremely important detritivores — they consume decomposing plant and animal parts, as well as feces — that help to rid the landscape of dead animals, an ecological role integral in the recycling of nutrients in ecosystems.
These flies have the ability to smell dead animals from over a mile away. The fact that flies arrived just seconds after I put out the bait is a testament to their numbers. Female blowflies will immediately start laying eggs, using a tubular projection off their hind ends called an ovipositor. The eggs quickly hatch into larvae (called maggots when talking about flies) and the larvae start eating.
Just like butterflies, blowflies then pupate in a small capsule. This is when the organization of the body is completely changed, resulting in wings, legs, eyes and so on. Reorganization complete, the capsule opens and out comes a fly.
Humans are large animals. As a result, we tend to pay attention to other large animals, but we seldom think of the myriad smaller creatures with which we share the planet. They are everywhere, they are important and they need to be understood.
Perhaps Wilson said it best in “Half Earth” when he said, “To those who think nature consists primarily of plants and large vertebrate animals, I say look about you at the little things that run the earth.”
If after reading this column, only one of you is curious enough to delve deeper into the world of insects, then I consider that success.
Bill Danielson has worked for the National Park Service, the US Forest Service, and the Massachusetts State Parks. He has been a professional writer and nature photographer for 19 years and he also teaches high school biology and physics. Visitwww.speakingofnature.com for more information, or go to Speaking of Nature on Facebook.