All the little six-legs

 kw: book reviews, nonfiction, natural history, insects, surveys

Let's get some technical stuff out of the way first. There are 28 orders of insects. After the graphic, I'll explain a bit:

We all are familiar with most of the kinds of critters in the upper third of the diagram, and some of those in the left half. The "big four", that encompass about 80% of all insect species are the beetles, the butterflies and moths (butterflies are specialized moths), the true flies (including mosquitoes), and the wasps and bees and ants (bees and ants are specialized wasps).

What is an order? An order is a broad classification in the middle of the scale of taxonomy, which is the hierarchical "tree" of relationships. In brief, according to a structure first set in place by Carl Linné (Linnaeus) in 1758, the primary categories are these:

• Kingdom (the main ones in our experience: plants, animals, fungi, and bacteria. There are others)
• Phylum (all vertebrates are a phylum. Insects are in the phylum of arthropods, or "joint-legged")
• Class (major categories within a phylum. Insects are a Class. So are all the mammals, among the vertebrates)
• Order (mid-level categories within a class; differentiated by broad similarity of form and lifestyle. So all the beetles are in one class, Coleoptera)
• Family (lower-level categories within an order)
• Genus (a category for one or more similar species. One genus of butterflies is Danaus, and one genus of human-like apes is Homo)
• Species (the lowest category. A species is always appended to its genus, and such a binomial is always italicized. A human is Homo sapiens, and the monarch butterfly is Danaus plexippus. You probably know Tyrannosaurus rex, the big meat-eating dinosaur)

Now to the book: In 2918 the American Museum of Natural History published Innumerable Insects: The Story of the Most Diverse and Myriad Animals on Earth, by Michael S. Engel, a Research Affiliate of the Museum. It's a kind of coffee-table book, not quite as large as the usual coffee-table book. While there are lots of illustrations, there is plenty of explanatory text. The pictures are a treasure. The American Museum also houses one of the great collections of rare books on natural history, and this volume is illustrated with a few hundred selections from the past few hundred years of "insect literature".

For example, the artist Jacob Hoefnagel illustrated one of the first books devoted to insects, Diversae Insectarum by Claes Jansz, published in 1630 (The book's full title is very much longer).

This image is from the frontispiece of that book, showing just a hint of insect diversity. You can see about half the currently-known orders of insects represented here.

Innumerable Insects begins with a brief history of entomology, the study of insects. "Entomology" is sometimes used to cover related small many-legged things like ticks, spiders and scorpions, but they actually have their own fields of study.

There are about 1.6 million species of insects so far described. Depending on what is known about a species, the "description" is anything from a one- or two-page "letter" in a journal such as Nature to a many-page monograph that describes not only the morphology of the animal but its life stages and habits. It takes me about a minute to read the abstract on the first page of a journal article or letter. Just reading 1.6 million abstracts, so as to familiarize myself with all the known species, would take every waking moment (assuming 14 hours so I have time for meals and pit stops: 840 minutes/day) for 1,905 days, or 5 years and 11 weeks. I wonder how much I would retain… And this would only be possible if I had an army of assistants to run hither and yon, finding all of the descriptive letters and articles!

More than a third of insect species are beetles (the numbers in the tree above are a few years out of date). This illustration of sand beetles is part of a page from Biologia Centrali-Americana (An electronic version is available at the Smithsonian Institution). The volume on Insecta:Coleoptera was published in two parts in 1884 and 1887. The second chapter of Innumerable Insects puts this immense diversity in perspective. 

Moths/butterflies, flies, and wasps/bees/ants make up another third. Several chapters are used to introduce us to all the 28 insecct orders, one after another, grouped roughly by ecology and habit.

I was forcibly reminded upon seeing all the amazing illustrations that, prior to photography, a naturalist had to be an artist. The tradition continues, and it is still true that the best illustrations are drawn or painted rather than photographed. I particularly appreciate the Roger Tory Peterson Field Guides, with drawings that bring out the important features of every creature in a way a photograph cannot match.

The latter chapters introduce some special topics: social insects (ants, bees, termites, etc.); insect "languages", whether by sound or dance; camouflage; and pollination. It's well accepted now that pollinating insects—not just butterflies but also certain beetles, flies, and several others—co-evolved with flowering plants, and that this "collaboration" led to the very great diversity of both.

I had not expected so much fascinating information to be packed into a 200-page book that is about one-third pictures. Author Engel did a great job, presenting this all to us in such a digestible way. I am reminded of a much older book, Broadsides From the Other Orders by Sue Hubbell (1994), also about the insect orders. It has a bit of a different emphasis. The two books make great companion volumes.

And I could not close this review without showing at least one butterfly. This is Ornithoptera priamus, one of the bird-wing butterflies that enhance the beauty of the tropics. The illustration is from Natural History of Insects of India, by Edward Donovan, 1838.