Saturday, February 23, 2013

Our plans for the rest of the year

I love studying insects, their life histories, their behaviors, their distribution, and because I spend most of my time in Arkansas, a state rich in biodiversity, I especially enjoy studying Arkansas insects. And further, because I live on Crowley's Ridge, this isolated archipelago of hills rising out of the flat Mississippi Delta in NE Arkansas, I like studying the insects of Crowley's Ridge, with their unique nature and complement of relict and unusual species.

The way I like to operate is this: I like to pick out a particular group of insects, and put all my attention on them, I like to read everything I can about them, I like to go out in the field with my close-focusing binoculars and my digital camera with a macro lens, and find and photograph every one I can, and that involves learning what their special habitat is, and what they eat, and what time of year they are present, and what time of day. After two or three or five or six, or however many years I reach a point where I can recognize and identify by sight every species of that group I am likely to see in Arkansas. At that point I don't give up on them, I keep noticing them when I see them, I keep trying to get better pictures of them than I have, I keep trying to record special behavior that I have not witnessed before, but my heavy attention shifts to some other group that I want to learn about.

Of course I do all this together with Cheryl (with her sharp eyes she is usually the first to spot whatever we are looking for), and she has her own specialties, particularly moths and caterpillars, that I help her with.  Over the years we have followed this pattern with dragonflies, butterflies, robber flies, moth caterpillars, tiger beetles. For the last two years I have been specializing in grasshoppers. At the time I started on grasshoppers I could identify by name perhaps half a dozen species. Now I have photographed and learned something about 55 species (of perhaps 70-75 that might occur in Arkansas), and the point of diminishing returns has set in. We will go on looking for grasshoppers, but we have done all the easy ones, and from now on I expect we will only find two or three new species every year. Frankly what I want now, what I enjoy most of all, is not the familiarity of a well studied group, but the novelty and steep learning curve of a brand new group.

You can't really study a particular creature without being able to put a name on it. For that reason there are certain things I look for in choosing a new group to study. First of all, a reasonable number of species to get your head around. Tiger beetles, at one extreme, only have 23-24 species occurring in Arkansas. Dragonflies and robber flies are both in the neighborhood of 125 species in the state, butterflies maybe 150, counting all the rare vagrants, grasshoppers less than a hundred. That all sounds very possible. Plus the vast majority of these come out in daytime, making them much easier (and more convenient) to see. And the great majority are flying in the air, or running on the ground or through vegetation, again making them more or less easy to find. Finally, most of the species are visibly different from each other, so that you can pin them down to exact species. Contrast this with, say, beetles or moths, that occur in thousands, many only out at night, or are otherwise invisible, burrowing in the ground, or tunneling through dead wood, with long lines of species so similar they can only be differentiated by dissecting out their genitalia to study under a microscope. For my purposes I would find that unworkable. You can of course pick a narrow group within the larger group, for instance, tiger beetles, but not beetles in general, hawk moths but not moths in general (Cheryl likes moths anyway).

Finally, what makes a real difference, is to have a first-rate field guide based on modern principles, namely, designed so you can identify species while they are alive and in the field, through your close-focusing binoculars, aided by close-up digital photographs. The amazing modern optical technology makes it possible, but the field guide makes it oh so much easier.

I started out in the 80's with dragonflies, helping George Harp, the state expert, making his first collections. There were no field guides as such back then, and we had to catch the dragonflies, make specimens out of them, and identify them by looking at the wing veins under a dissecting microscope. The old Peterson butterfly field guides were not "field" guides at all. They had pictures of rows of pinned specimens with their wings held in artificial positions. The only way you could learn them was to make your own collection and pin them in that artificial way and hold them side by side with the pictures in the field guide. I did that when I tried to learn the butterflies back then, and I found that it worked all right for the  "true" butterflies, but the skippers (which are almost 50 percent of the butterflies), were nearly impossible to identify that way, and I gave up in discouragement. Instead I started, with my colleague in insect studies Herschel Raney, to study robber flies, and there were no guides of any kind and we had to start from scratch, collecting species, getting technical papers on different groups, running our specimens through identification keys under a dissecting microscope. Finally, with my web site "The Robber Flies of Crowley's Ridge," I made my own field guide for Arkansas robbers, so far the only robber fly field guide that there is.

But then after the new optics came out that allowed you to study insects in the field from four feet away at eight times magnification, allowing you to see fine details of pattern and structure, the new generation of field guides started coming out one after another, guides illustrated by photographs or paintings of living insects in their natural postures that could really be used to identify species in the field.  This all transpired around the end of the century, which conveniently for me, was about the time I retired, and could give these new studies full time. Glassberg's "Butterflies Through Binoculars: The East," came out in 1999, and in the same series Dunkle's "Dragonflies Through Binoculars" in 2000.  Later Capinera's "Field Guide to Grasshoppers, Katydids, and Crickets" came out in 2004, Wagner's "Caterpillars of Eastern North America" in 2005, Pearson's "A Field Guide to the Tiger Beetles" came out in 2006, and then more, and constantly improving, butterfly and dragonfly guides have been coming out almost yearly, and a quite full general insect guide, Eaton's "Kaufman Field Guide to Insects of North America," also in 2006.

These books have immeasurably enriched Cheryl's and my lives. They have led us to wild corners in Arkansas we might never have visited, and they have turned on lights, one after the other, that enabled us to see for the first time things that had always been right before our eyes. Now a fine new guide has come out, and I think it is going to direct our lives for the next year or few years. It is "Common Spiders of North America," by Richard Bradley, and very handsomely illustrated by Steve Buchanan (University of California Press, 2013). It's not quite the "ideal" group, as I was describing it above. I know, I know, they aren't insects, but that's not a problem, they are equivalent arthropods. But many stay hidden under stones and bark, or in burrows, etc., or only come out at night, and there are long lines of lookalike species that need dissection to identify, and who knows how many hundreds of species there are. But I don't care: The illustrations in the new field guide won me over at first glance.

Actually, we have always been very fond of spiders. I often kept them as pets when I was a kid, and the big Argiopes, the Black-and-Yellow Garden Spiders, in our yard every summer are virtually pets (our Brown Recluses, for that matter, that live in the house with us, are nearly pets, but we keep a little more distance on them). We have never, however, given spiders in general the close attention they deserve with their many extraordinary behaviors that seem so close to reasoning. When we have been out in the field, and I was concentrating on robber flies or whatever my current obsession was, Cheryl always took pictures of interesting spiders, and I did too, I guess, though never as many.

So that's been the beginning: I have recently gathered together all our spider pictures from the last eight or nine years, put them in a Picasa Web album, and then used the new field guide (with lots of help from BugGuide) to put names on them. It turned out we had about 70-odd species, and although a lot of the ID's are a bit dodgy, I have put some kind of name on most of them. Now I can't wait for the weather to warm up, so I can see the first spiders come out. Let the good times roll! (Unless you are so benighted that you don't like spiders. Well, if you don't like them, I will just have to educate you.)

Let's start with a preview, anyway.  The Jumping Spiders (family Salticidae), make up the largest spider family (over 5000 species worldwide), and are one of the most popular groups. Most spiders have eight eyes, and the size and arrangement on the head of these eyes helps identify the different families. In the case of jumping spiders there are two enormous eyes front and center on the very flat face which give them extremely sharp vision and accurate triangulation. They don't spin webs; rather, they spot their prey from a distance and stalk it like a cat, and when they get close enough, they spring, again just like a cat. They come in an infinite number of shapes and color patterns, but they are immediately recognizable by their big eyes and flat faces, and their alert cautious walking, constantly switching around to look at whatever moves ahead of them, and are also recognizable by their responsiveness to you. If you look at them, they will immediately turn and look back at you.

More than that, they have elaborate courtship dances in which they wigwag their long front legs at each other. If you hold up your two index fingers, you can wigwag at them and sometimes get an answer.

Mimicry is a common theme among arthropods. For various reasons, a number of jumping spiders are amazingly accurate mimics of ants. Is it because ants are full of formic acid so most things don't want to eat them, or is it so they can cozy up to a real ant and have it for dinner? Those that mimic ants race along in a straight line exactly like ants, and walk on their back three sets of legs, waggling their first set of legs out in front of them like ant antennae. Look at this nice example.

They are all, of course, terrific hunters.

We will be learning all this, but I am guessing that the first warm sunny day in March, the first Jumping Spiders will be out. It will be fun to see how many species we can find over the year. I'll make another rash guess: 25 species of Jumping Spiders by December.

Monday, February 11, 2013


We have all heard the stories of paleoanthropologists digging up a single tooth and working out from it that it belongs to a new species of early-human, and saying something about its diet and behavior and taxonomic relationships and deriving a natural history for it. I myself love creating complex theories out of minimal evidence and feel I missed my calling by becoming an English teacher instead of a paleontologist (Cheryl thinks I did the next closest thing by becoming a fiction writer).

I might very well have gone the other way. As a kid I loved skulls and began building up a collection of them that I'm still adding to, and which is sitting on an entire bookcase shelf just across the room from me as I am writing this. I used to (well, I'm still doing it) keep an eye out for roadkills that weren't too badly smashed up, and if I found some animal whose skull I particularly wanted, I would set it on the shoulder off the road, somewhere out of sight from others (who might steal it from me?), but where I could find it again, and then I would come looking for it several months later. You try to gauge just how long to leave it, to some period where the bugs have mostly cleaned it up, but it hasn't totally disintegrated. But if it was an especially choice animal I would cut the head off right then and bring it straight home and put it in a jar or bucket of water and stick it in the farthest away corner of the yard to let it "macerate." The far corner because it wasn't pleasant to see, and it could really stink. And it took forever, months and months. If you timed it just right, when you poured all the stinky goop out on the ground, the purest whitest most beautiful skull suddenly appeared out of it, which a gentle hosing (trying to be careful no loose teeth were lost) and drying would make into a perfect specimen. If you waited too long every separate bone would fall apart and you would be left with a 1000-piece 3-D puzzle to glue back together.

Skulls are beautiful intricate sculptural objects, and, fair play to the paleontologists, you can learn practically everything about an animal from its skull, especially from its teeth. The reason I am going on about them here is that my son Gawain and his friend Heather saw a book they knew I would like and got it for me as a Christmas present. The book is called "Skulls," and is by Simon Winchester ("The Professor and the Madman," "Krakatoa," etc.), and is about Alan Dudley, who was like me as a kid but raised up a few levels of magnitude, and now has the largest personal collection of skulls in the world. The text says something about Dudley's obsession and so on, but the text is very brief, and mainly the book is page after page of photographs (by Nick Mann) of the skulls themselves, and (at least for an old collector like me) they are wonderful. They have made me look again at my own I admit rather dust-covered collection, and I am pleased to notice that, on its tinier scale I have also tried to create a representative group of different types, particularly of mammals.

What I'm going to do here is to show (well, show off) a few of my own skulls and point out some of the ways the teeth indicate diet and even behavior.

Here for example is an Eastern Mole. It's an insectivore, and this is  indicated by its undifferentiated teeth. They are virtually all just the same, simple pegs, which are ideal for picking up an insect or worm, and perhaps ripping it into chunks small enough to swallow without much chewing,

People sometimes ask me if moles are related to mice and rats, because they are similarly small furry animals that live in the ground. But look here at this skull of a Brown Rat. It has highly differentiated teeth. It has two enormous incisors in the front, designed for digging burrows in the ground, or biting off thick plant stocks. It is an omnivore that is fond of eating meat, but there would be no room for canines behind those incisors, so it has no canines, and uses the powerful incisors instead as killing weapons. Any food that comes into the mouth goes straight to the back of the mouth to be chewed up by the molars.

Here is another animal totally unrelated to moles, an armadillo. But because it has a similar insectivorous diet, it has evolved a similar mouth full of simple peg teeth. The teeth, in other words, indicate diet, but can be tricky to use to show taxonomic relationship.

Here is another example of this fact. This is a harbor seal. Note in the second picture how the very large brain has been flattened out to the side to keep the profile of the skull flat, unobstructed, and aerodynamic for smooth fast swimming. But note especially that the canine teeth of this carnivore have been somewhat reduced to be more the size of the other teeth, and all of the teeth are tending towards being pointed. Fish are so fast and swerving that it would be difficult to use an accurate bite with canines to capture them. What is needed is a mouthful of sharp points so that any kind of bite can impale the slippery prey and hold on to it.

Now look at this: Here is a river otter, a totally unrelated animal, a kind of aquatic weasel, but also an animal that catches fish by swimming swiftly after them. Note here that, almost identical to the seal, it has a flat aerodynamic shape to the skull, similarly with its quite big brain (does that mean fishermen have to be smart?) squashed out to the sides to keep the top flat, and most similarly its carnivore's teeth have been modified to be sharp fish-snaggers.

Here is the skull of a domestic cat. The cat is a total carnivore; virtually one-hundred percent of its diet is meat. What you see are very long sharp canines with a gap behind them so that they stand clear of other teeth and can be stabbed their full length into their prey. In this case they are especially designed to go around the neck bones of their small prey and quickly break the spine. Then notice how few back teeth they have. There is not a heavy complement of molars, because cats don't do any chewing. Instead the few molars they have are modified into carnassials. The upper and lower teeth fit together like the blades of a scissors and their function is to slice. They cut meat into small pieces and it is then swallowed directly. The second picture, from the front shows another carnivore adaptation. The incisors are practically nonexistent. Incisors are most useful for biting off plant material, something a cat has no use for.

Here is a bobcat skull. Except for the size (which you can't tell from this picture) it is virtually identical to the house cat. Cats are in fact perfectly designed for their stalk-and-leap style of hunting, with forward-facing eyes (the snout shortened so as not to be in the way) for accurate triangulation, the teeth reduced to a functional minimum (it would take a longer snout to fit more of them in). When cats evolved to fit into another niche, it was to hunt a different size-range of prey. They didn't change their perfect design, they just got larger or smaller.

To show what I mean, here is a puma. (This skull unfortunately has the upper canine broken in half, so in the second picture I will show it turned around to show the length of the full canine.) It's a bit more massive, but it's still the exact same design.

Here they all are together.

Here is a carnivore with different behavior, a coyote.  A cat often makes a surprise leap on sitting prey, and can set its canine teeth accurately. A coyote is often chasing swift and elusive prey (rabbits, for instance), and with its long jaws with canines at the tip end, can nip repeatedly until it gets a good hold, and then can bite to make the kill. But also, as the second picture shows, it has much better developed incisors than a cat, because coyotes eat vegetable food as well, melons and fruits, and for that, as the third picture shows, it has a full set of molars for chewing.

There's one more skull I want to show.  This one reminds me of a time I was attending a conference in Washington D.C. and had a few hours off and wandered into the Smithsonian to some rooms full of skeletons and particularly skulls. One room was all primate skulls, from tiny monkey skulls the size of a hen's egg to enormous orangutan and gorilla skulls. No one was around and I was sort of daydreaming as I entered the room, and suddenly I was surrounded by staring faces. After all, we are all primates. These had big craniums, and most had flat faces with two big staring forward-facing eye sockets. I was briefly quite startled. They were all human faces, humans of all different sizes, but what was most unsettling is, they all had big powerful canine teeth. They were monsters, demons, vampires. Several years ago when Gawain came back from a trip to Brazil he brought me a monkey skull, one of my prized possessions. If I hadn't known it was a monkey, if I was just handed the skull and was asked what I could gather about its diet and behavior, I would have guessed that it sneaked into our bedrooms at night and sucked our blood.