The high mathematics of grasshopper identification

We are in serious drought now, last summer repeating itself. One hundred degrees was forecast for the day. It took me a long time to learn, but I have, finally, learned that on this kind of day there is no point driving a long distance to one of my favorite spots to look for insects, because they won't be there, and I can knock myself out dragging through the heat, and I won't find a thing. Butterflies won't be flying, because in the heat the flowers shut down and produce no nectar. Robber flies won't come out, because there will be nothing out for them to catch. Tiger beetles will stay buried under the sand, dragonflies will roost in the shadows. Grasshoppers, good old grasshoppers, will be out, but they tend to stay in the open barren places of straight overhead sun where you can't stand to be yourself.

I decide to go to some place nearby, and just go for the morning when the heat is still in the bearable 80's. I go to the Jonesboro Nature Center, and walk out on the prairie. It's alive with grasshoppers, and there are three species I find myself concentrating my attention on. Oddly, these all require geometry to identify.

Let me show you a picture of one of the three species, and then I'll explain how it works.

This is the rather inappropriately named Northern Green-striped Grasshopper. Females are green and no doubt have a green-stripe somewhere; males like this one are brown and are green-stripeless. You identify this species by a line through the eye that gives it a sort of sad, droopy-eyed expression, by the narrow ridge on the pronotum (the pronotum, on grasshoppers, is the sort of saddle-like cover that goes over the thorax), and by a sort of sharp narrow ridge on the upper side of the big hind femur (the upper long joint of the leg). As a final confirmation, this species has brown hind tibiae. The tibia is the skinny second long joint of the leg. On grasshoppers, the hind tibia is hidden under the femur. It is often a bright color, and is revealed during sexual displays. Dull brown on this species, and, as I say, very difficult to spot.

Now, the Northern Green-striped Grasshopper is one of the most common grasshoppers in the United States, found everywhere except in the West, and in Florida.  It has, however, a lookalike twin, the Southern Green-striped Grasshopper. According to the published range maps, that one doesn't occur in Arkansas, it occurs only in the Gulf states and in Florida. Well, I carefully examined many pictures I had taken of the Northern last year, and realized that one that I took a picture of was the Southern Green-striped, completely out of its known range. Here's how I could tell, and here's where the geometry comes in. If you look at the above picture again and look at the back edge of the pronotum, you'll see it makes a sharp-pointed angle facing backwards. The angle is acute, which means it is narrower and more pointed than a right angle would be. On the Southern Green-striped the shape is a right angle, and if you think you see that right angle, you can get confirmation by getting a peek at the hind tibia, which, in the Southern, is bright blue. Here's the picture.

What I want to find out this year is just how common this Southern version is. I know it is much scarcer than the Northern. On this day I was trying to check all Northerns that I saw, and I didn't find any Southerns. Maybe they don't come out until later in the year.

Luckily it was a Monday, and the Nature Center is closed on Monday, so there weren't any people around to wonder what I was doing out in the middle of the prairie crawling around on my hands and knees.

On this day, there were two more species I was interested in, and by odd coincidence, each of them had a lookalike twin, and in each case the twin species could be identified by the same geometry.

The first of them was the Orange-winged Grasshopper. I think I have mentioned this one on previous blogs. The Orange-winged has a twin, the Coral-winged, which, according to the books, occurs at the same times and in the same places as the Orange-winged, but I had never knowingly seen it, so it was one of my major targets for this summer. When I had gotten a little way into the prairie I chased up a large grasshopper with bright orange wings. It didn't fly far, and landed out of sight down in a thicket of sticks and dried grass stalks. I searched carefully and finally spotted it. It was a large female, and they would rather hide than fly, so this one stayed still while I lifted the sticks, and bent the grass stalks, out of the way so I could get a shot at it with my camera.

The Orange-winged, a very common species, comes in a green phase, and in a gray-brown phase. This one was a reddish brown such as I had never seen, and it occurred to me that maybe the Coral-winged came in such a color. So very carefully, trying not to startle it, I positioned myself for a directly overhead shot.

The hind femur on the right side is slightly out from the body so I could catch a glimpse of the blue at the base of the leg on the inside. This is diagnostic for Orange-winged, as the Coral-winged does not have this feature. But the blue is not always revealed, and often when you try to get in this position, the grasshopper takes off before you can photograph it. But I didn't really need to see the blue, because in this case it is the Coral-winged that has the angle at the back of the pronotum acute. The angle on the Orange-winged, as you can plainly see here, is a right angle.

So, I must go on looking for the Coral-winged.

The third species I was concerned with, and this one was the most fun, was the Ridgeback Sand Grasshopper. Like the other two it is in the group known as the Band-winged Grasshoppers. These are typical grasshoppers of open places, long-winged strong leapers and flyers, often with bright colored wings, and a tendency to go clickety-click as they fly. Except for the wings, mostly they are in the colors of the sand and rocks and dry grass they live in. The Ridgeback Sand is a typical member, looking like he is made out of the sand he is sitting on. He is noteworthy, however, for the extremely elevated crest on his pronotum.

If you look at that very high ridge on the pronotum you will notice, about a third of the way back from the head, a deep furrow, or sulcus. Well, this furrow is very deep, in fact it cuts half way through the ridge. So this was my fun: I spent all morning chasing them around trying to get at exactly the correct angle so that I could take a picture right through the the cut. Here's what I finally managed.

There were a lot of these present on the prairie, and courtship was going on. A number of males would approach a female all doing their wild courtship dance which mainly consisted of flashing their hind tibiae and waggling them about. Like many grasshoppers that blend invisibly into their drab colorless backgrounds, their usually concealed (repressed?) hind tibiae were their one chance to dazzle the females with brightness. Here's a shot of one I got that was almost going too fast to keep in the view-finder.

This species, in keeping with my theme, also has a lookalike twin. The new wrinkle is, neither one of them should be found here. The Ridgeback Sand Grasshopper, according to the range maps, is found in the southwest corner of Arkansas, and here it is in the northeast in Jonesboro. Its nearly identical twin, the Mottled Sand Grasshopper, is only found to the north of us, in fact, north even of Missouri. Since neither of them belonged here, I had to make sure which one I was seeing. And the trick once more is to look for the angle on the back of the pronotum. In this case, it's the Mottled that has the right angle, and the Ridgeback that has the acute. Here it is: I'll let you decide for yourself.

A new habitat

If you want to expand your study of insects, and what rational person would not, the best thing is to visit a completely new habitat, where like as not you will find a completely new suite of insects.

Let me recommend a road-kill opossum.

One morning when I went out I found a freshly dead opossum on the road right in front of the house. It was not damaged externally, but I knew the longer it stayed, the more smashed up it would get, and the worse it would smell. So I carried it down the street fifty feet (there was no other house around) and dropped it about fifteen feet off the road on the far side, which was railroad right-of-way, so again no one would be offended by it.

You would think a dead thing in Arkansas in the heat of summer could make a whole neighborhood unlivable, but I had noted in the past that dead things didn't last any time at all. You and I may not look at it this way, but a dead opossum is a whole mountain of free meat, and unlike vegetable food, meat is pure concentrated energy.  A lot of creatures will want their share of it, and they each have their methods of getting it. Bacteria, for instance. For invisible things they are shrewder and more organized than you think. You know that after a few days a dead thing begins to stink, and you probably think that is some natural chemical product of the rotting process. It turns out that is not true. There is no part of the rotting process that necessarily results in a bad smell. The bacteria manufacture that smell, and make it as horrible as possible, to drive vertebrates scavengers away from the corpse, and save it for themselves. Bluebottle and Greenbottle Flies are their chief competitors, and within very few days these turn the corpse into a frothing mass of maggots, again too nasty for most other scavengers to deal with. But within those first few days there is an opening for a host of small creatures to get in on the feast, and I decided I would observe the process.

The next morning I went out there with my camera, sat comfortably by the opossum, and noticed that, for a corpse, it was already full of life. Not long after life stops there is some smell of death, too subtle for us to perceive, but small creatures all around begin moving towards it. First of all, it was already buzzing with Greenbottle Flies, and their eggs were already hatching out the first maggots. But soon big droning beetles were arriving. For some reason, many of the beetles that feed on carrion have shortish elytra with the pointed tips of their abdomens sticking out behind. The first one like this I saw was Necrodes surinamensis (the Latin names frequently have nicro- or necro- or Thanato- all meaning death).

Now here is how the competitive jockeying plays out. These beetles, like the flies, lay eggs, and their young feed on carrion. The beetles themselves do not feed on carrion, they feed on the fly maggots. In other words they are clearing out some of the competition for their larvae. Here is one gulping down a maggot, with the Greenbottle Fly looking on.

Here's another beetle, Oiceoptoma inaequale, with a similar life history. But if you look closely, you will see that this one arrived with a small load of tiny flies on its back. These flies, Milichiids or something related, feed on the fluids of dead animals, and their gambit is to ride on the backs of carrion beetles or robber flies or other predators, or sometimes hang out around spider webs, and when they are brought to oozing meat they climb off and grab their share.

Here's another, slightly more colorful, beetle in the same genus, Oiceoptoma noveboracense. Perhaps we need a bit more color in all this blackness.

Here is the only one of these you are likely to see away from a corpse. This is Necrophila americana, the American Carrion Beetle (a very common beetle, not to be confused with the endangered American Burying Beetle).

The odd pattern on the thorax of this rather large beetle is meant to mimic the yellow fur with a bald spot in the middle found on the thorax of bumble bees. You wouldn't believe it when you see it here, but when it is flying towards its next cache of carrion with a loud buzzing flight, you have to look very carefully indeed to see it is a beetle and not a bumble bee. There is one other thing to remark here. This beetle arrived with a load of lice on its back (you can still see one left just behind his head). These were not blood-sucking lice making his life miserable, these were predatory lice and he was delivering them to a place where they could feed on their favorite food, fly eggs. In other words, they got a free trip to the eggs, the beetle got some help eliminating flies from competing with its own larvae. You begin to see how programmed this whole operation is.

Various species of rove beetles were also attending. They carry the short elytra and protruding abdomens to an extreme. They fly in and then fold their wings up under the very short elytra with the complexity of folding the flag at sunset. Here is a rather handsome one, Platydracus maculosus.

Finally, here's a tiny fly, Prochyliza xanthostoma, that's quite comical to watch. It specializes on the dry skin that remains when everyone else is finished, or at any rate, that's what his larvae feed on. This is the male with his complicated head structure (which the female doesn't have). He stakes out a good territory on the carcass, because that's where the females will want to be, then battles off other males with ram-like butting contests.

Maybe there was more of interest, but by then things were getting higher than I could put up with any longer.

Moths

It's the longest day, the first day of summer. But summer isn't looking as attractive as it did in early spring when everything was mild and wet without being too wet, and things seemed perfect for a good insect year. Now it is hot and dry and everything is set for a drought, which is entomological disaster. This is at least a small part of why I have decided to study grasshoppers: They seem to do all right in a drought. Insects I specialized in in the past, butterflies, dragonflies, robber flies, tiger beetles, are really diminished by drought. Particularly drought alternating with flood, which has been the story the past few years, and all of these groups seem to me to be in poor numbers, and every time I begin to hope they are coming back, we are hit with another drought or flood.

Cheryl however is interested in moths, and makes me think maybe that is a way to go. At least you go out in the cool of the evening to look for them, and usually don't have to go farther than your front porch where you have carefully left the light on, and can whip back inside when the mosquitoes become intolerable. There are disadvantages to moths, of course. There are 11,000 of them in North America and that is sort of hard to get your head around, and they are mainly gray and dull and all look alike. Well that's what I thought, but now I am learning that if you take them one at a time, and especially if you photograph them so you can study them carefully afterwards, they are sometimes really bizarre, and often subtly beautiful. Here's an example of each (you can decide for yourself which is which).

This last one is particularly numerous at the moment. They are sitting on the screens of all our windows at night and make up almost all of the moths that come to our porch light. The problem is, which of the 11,000 species is it? We have been paging through our new Peterson Field Guide to the Moths stopping at groups with this shape, the wings folded like a tent over the body, the head with a cockatoo crest, and have decided it is not a Prominent or a Looper or a Sallow, and we have stopped at Pickerelweed Borer. This is especially appealing because most of the marks on the moth seem right, plus we have never before had a bigger or more flourishing bed of pickerelweed in our pond, which could be the source of this invasion of the adult moths.

We also like this choice (remember it is still guesswork on our inexperienced parts), because it is such a neat moth. Here is its life history (which I am gleaning from Wagner et al., Owlet Caterpillars of Eastern North America): Eggs are laid above above waterline on pickerelweed. The caterpillar hatches out, bores into the plant tissue and goes down under water where it feeds. When it has finished that part of its life, it bores its way out, then floats to the top, and swims ashore (its tail end going back and forth as a snake would swim). It then crawls under old wood or other debris, where it spends the winter, then in spring it makes a cocoon in a cell in the ground or in rotted wood, the adults emerging in early summer to flock to our windows.

This is not the only very visible moth activity at the moment.

Right now there are no Monarch caterpillars using our milkweeds, but they are not going to go to waste. If you turn over a leaf at the right moment here is what you might find:

These are the eggs of the Milkweed Tussock Moth, and these spell something close to doom for the milkweed plants themselves (though they always come back no matter how badly they are defoliated). The Milkweed Tussock Moth caterpillars will come in droves and feed side by side, devouring every leaf of every plant one by one. I wasn't quick enough to notice the eggs this year (the photo is from a previous year). When I first thought to look, they were already hatched and on their way.

Some have already molted out of their earliest stages to show their full tussockness, and also showing their black white and red warning coloring, since they have imbibed from the milkweed the same powerful heart poisons that the Monarch caterpillars ate earlier in the year. When this plant is eaten to the nub (when I took this picture they were only on the third or fourth leaf) they will march to the next and they will join other groups or split up individually and one way or other make sure they visit every corner of the yard.

The Monarch caterpillars turn into the superb Monarch butterfly. These spectacular tussock caterpillars will turn into the plainest jane of all the moths, a complete reversal of the Ugly Duckling story.

This often, it seems to me, is the case with caterpillars and moths, which is why I love caterpillars, but Cheryl can only fleetingly get me interested in their parents.

Postscript: The world (or anyway my world) has a way pushing back against me the moment I make a large general statement, such as "Spectacular caterpillars lead to plain uninteresting moths." I typed those last words, then went into the house from my study to ask Cheryl to look at my blog and prune out the misspellings and gross factual errors. While I spoke to her I glanced at the aquarium on the counter and noticed a big moth that had not been there yesterday. In the middle of May Cheryl had found a spectacular big hornworm on our ash tree, the caterpillar of the Waved Sphinx moth, and we had brought it in and put it in that aquarium.

It was so voracious we had to bring it a new cluster of ash leaves every day. On the 29th of May it buried himself under the loose soil we had prepared for it, and on this day, the first day of summer, scarcely three weeks later, this beautiful big Waved Sphinx Moth had eclosed. Here is a picture of it in the aquarium.

We waited until nighttime then took it outside to release it. Here is the last view we had of it. Well, maybe this moth wasn't a total disappointment.

Waiting in the wings

It's easy to get the impression that insect or arthropod life explodes in mid or late summer. For instance, if we haven't been paying close attention, it seems like suddenly in the heat of summer our yard is filled with big golden garden spiders, Argiope aurantia.

They are formidable hunters, sitting on their zigzag stablimentum in the middle of their web. If they feel the vibrations of a large animal, such as you, approaching, they begin violently jerking back and forth, in order to attract your attention to their presence. You, or a dog or a cow, will much prefer to walk around them to getting caught up in their nasty sticky web, and they much prefer not having to remake it. Before long they will be catching your favorite dragonflies or butterflies. They often catch and eat tree frogs and occasionally catch hummingbirds (which we rush to rescue). We're fond of our spiders, but sometimes move an Argiope out of a very rich butterfly area to a quieter spot.

But the point is: Where do they all suddenly come from?

Well, they were all there to start with, but they were in their early tiny forms staying out of sight low in the vegetation. If you watch for them, in the spring you will begin seeing a white circle about the size of a nickel deep down in the grass. This is the early form of their stabilimentum, woven so densely it is opaque. If some little predator comes by, the spider can flip around to the other side in an instant to be out of sight. As the year progresses, the circle gets more tightly woven and bigger until, after a certain number of molts, the zigzag begins to develop. Here is the progression I have seen so far this year.

But spiders aren't going to be the big news this year. The signs are already here. When you walk through grassy places, or flower beds, you hear a skittering ahead of you, and see the movement in the vegetation, as if someone were scattering small gravel. It's grasshopper nymphs. Grasshoppers don't have a full metamorphosis. They come from the egg as tiny grasshoppers, more or less like the adults, but without developed wings or genitalia. With each molt they look the same, only larger. They still are only that skittering in the grass (though Cheryl complains they are eating her flowers). Here are a couple of nymphs that with a few more molts will be large and voracious Differential Grasshoppers, with long wings for powerful flight, powerful chewing jaws, and judging by how many I am seeing now, they will be in destructive numbers.

It is not until the last one or two molts that suddenly they become visible, large eating machines. Agricultural entomologists are predicting plagues this year. It will be a problem for farmers, who will need to defend their crops. But in a way it will be a boon for me, as I am studying grasshoppers this year, and it will certainly be a boon for the Argiopes, who feed heavily on large prey like grasshoppers.

This isn't always news

There are two lookalike butterflies, The Painted Lady, and the American Lady. They are both medium-sized orange and black butterflies, very similar at a glance, but with a number of different details in their pattern that help to separate them. The most obvious is when the butterfly lands with its wings closed over its back. The American Lady shows two big eyespots.

Year in year out the American Lady is always a reasonably common butterfly. The same cannot be said for the Painted Lady. Sometimes it is super-abundant. I remember once walking about a quarter of a mile down the railroad tracks in front of my house and counting well over 100 Painted Ladies. I remember another time standing in one place and counting over 80. But this is balanced against other years when I have not seen a single one. They are known for making long (not very well understood) migration flights, and perhaps when I saw the big numbers I was witnessing something like that. But at the moment, at least here in north-east Arkansas, we are in the midst of a barren period. I honestly cannot remember the last time I saw a Painted Lady. Certainly not this year. I sort of remember seeing a single individual last year.

Up until now. I just went out to the front yard, and the "American Lady" visiting flowers did not look right, so I gave it a second look. And there it was: A Painted Lady. Its most obvious mark is that, when it is in the same position as the above picture, instead of two big eyes, it shows a number of small eyes.

Now the question is, is this the single Painted Lady I will see this year, or is this the first member of a major invasion?

Still trying to keep up

Everything moves so incredibly fast. I see some interesting things, I take some nice pictures, I think, This could make a blog. But by then I've seen some more interesting things, taken some more interesting pictures...

Just a short time ago the Common Milkweed plants down our driveway were in full bloom. The Monarch caterpillars were chewing them up as quickly as they could, nice butterflies, like this Great Spangled Fritillary (they deserve the fancy name), were visiting them, and now already the caterpillars have gone off to make their chrysalises, and the flowers are over with.

In fact the butterfly-attracting flora has shifted to the Pickerelweed now in full bloom in our pond at the back of the yard. Lately the rather rare Dukes's Skipper has been visiting them. It normally stays in wetlands where its caterpillars feed on sedges, but the wetlands near us are now bone dry, so it's coming to us (to be sure I have to refill the pond every few days, as the surrounding trees suck it dry).

My sister came out from California for a visit, and we took her up to Crystal Bridges, which we wanted to see ourselves. The museum architecture and the painting collection were as good as everyone has been saying, but of course we made it a point to go early, a few hours before the museum opened, in order to walk the equally famous trails. They were beautifully and naturally planted. Here's a prairie section:

Best of all, the trails were alive with birds and butterflies and other interesting creatures. In a previous post I showed a picture of a tan-colored damselfly which was the female of the Springwater Dancer. On the trails here, we found the brilliantly colored male of that species. And then a little later we found another colorful insect, a day-flying moth, the Eight-spotted Forester.

But my sister, who is only politely interested in the tiny things I have been dragging home since I was big enough to walk, nevertheless found the most exciting thing of the day: an Underwing caterpillar. Underwings are a very popular group of moths. There are dozens of them, and they share these traits: The are largeish in size, they spend the day clinging to the side of treetrunks, where the cryptic coloring of their wings makes them virtually invisible against the bark. But if they want to startle an approaching predator that seems to have spotted them, they suddenly open their wings, revealing dramatically colored red or black underwings. Most of the species are very similar to each other, differing in only fine details of pattern, and part of the fun is trying to sort out what species you are looking at. Here's a picture I took of one last year (it's a live moth, by the way; that gray thing on its back, whatever it is, is not a pin).

Well, we're very fond of caterpillars, photographing them, sometimes raising them (we have a Picasa Web Album of them http://picasaweb.google.com/norman.lavers/SomeMothsOfCrowleySRidgeIII#), but we had never managed to find an Underwing caterpillar (they are even more cryptically colored than the adult moths). And now my sister had found one that we had both overlooked. This picture of it will show you how cryptic they are:

Now some of my readers may wonder what all the fuss is about, over a little gray wormy thing, but that is because they have not yet discovered the wonder of caterpillars. Caterpillars are at the base of almost every food chain you can imagine. Surely half of all insects, high percentages of birds, are designed to feed on caterpillars. Caterpillars, not wanting to be consumed, have over the millions of years devised incredible stratagems to avoid being consumed, and their predators have devised more stratagems to be able to find and eat them, to which the caterpillars have responded by devising even more incredible stratagems. Browse my album and you will come away loving caterpillars, as every enlightened person should.


Even as I write this we are gearing up for the caterpillar season. Butterfly and moth caterpillars are often very specific in the plants they will feed on, Monarchs, for example, only feeding on plants in the milkweed family. We try to plant at least one new plant each year that some particular caterpillar feeds on. A few years ago, for instance, we started a Pipevine (Aristolochia) in our backyard, which is the food plant of the Pipevine Swallowtail butterfly. Aristolochia, itself not wanting to be eaten, produces a powerful poison, which protects it from most things. But the Pipevine Swallowtail caterpillar has learned to sequester that poison in its own body, so that it becomes poisonous to things that would eat it. To make sure that every bird or lizard that might eat it knows in advance that it is poisonous, and so will leave it alone, it manages to look poisonous. Here's a picture of the ones we found on our pipevine plant.

Sphinx moths, the ones that hover in front of flowers like humming birds (many are nearly the size of humming birds) while they use their long tongues to drink the nectar, have caterpillars called "horn worms" because of the long spine at the end of their bodies. Cheryl, with her sharp eyes, spotted a Waved Sphinx hornworm in our ash tree. We love to raise these finger-sized caterpillars into adults, so we brought it in and set it up in an aquarium and fed it ash leaves by the dozen, which disappeared faster than we would have imagined. The caterpillar got bigger and bigger, then one morning was gone. We had filled the aquarium several inches deep with loose soil and leaf litter, and it had buried itself to form its pupa. Here is the handsome caterpillar we had; if all goes well, later we will show a picture of the moth it becomes.

But so far the most interesting caterpillar we have is one I picked up off the ground looking like it was dead. A number of hunting wasps feed their young on caterpillars. The adult wasps feed on nectar themselves, but their larvae are carnivorous. These wasps find a caterpillar, flip it over on its back, sting the nerve centers of each segment, then bury the paralyzed caterpillar underground and lay an egg on it. The caterpillar being alive stays fresh and juicy for the larva, and the larva carefully eats non-vital tissues first, to keep it fresh as long as possible. When the caterpillar is consumed, the larval wasp makes its cocoon, then emerges as a wasp and takes up the family business. What happens is, sometimes something disturbs the wasp, and it drops the caterpillar it is carrying. I found one of these, lying comatose on the ground, and brought it home to try to identify it. It looked to me in fact like an Underwing caterpillar, and I got out all my books, but I could not identify it further. For two or three days it lay on my desk, staying fresh and round, not drying out like a dead thing.


Then one day I stepped into my study, looked at it, and it had started moving slightly. I had heard of this happening before. If the larval wasp did not begin eating it at once, it would eventually recover from the paralysis of the sting. Now I really needed to identify it. If it recovered fully, it would need to eat, and if I didn't have the proper identity for it, I would not know what specific food it needed to have. So I took pictures of it and sent them to BugGuide, asking for a quick identification, and explaining my urgency. Here are some pictures of it.

Within hours the caterpillar expert (who signs his name shotguneddie) reported to me that it was the caterpillar of the Lunate Zale, not an Underwing, but a closely related species, and suggested I feed it blackberry leaves. We made a container for it and loaded it with blackberry leaves. For several days we could see that it was beginning to wander, but it was not feeding, and we thought perhaps it would not recover enough to begin normal life. Then one day we found fresh droppings in the container, and the leaves began disappearing. Here is a picture of it today. If it goes on to make a cocoon, and finally emerge as a moth, we will report on it.