Monday, February 27, 2012

Nicocles pictus and Schistocerca damnifica

The other night a large beautiful orange ichneumon came to the light of our kitchen window. According to our Kaufman Field Guide to Insects of North America by Kaufman and Eric Eaton it was an Ophion species, a parasite on large caterpillars. It was the same as or similar to one we had dealings with a few years ago. We had brought three Black Swallowtail caterpillars in from the garden and raised them, and when they made chrysalises we hung them on the wall of a back room. One morning in spring about the time we expected the butterflies to emerge I came in and saw a hole in the side of each chrysalis, and three of these ichneumons were at the window asking to be let out, which I did after I had shown them to Cheryl. We were a bit annoyed, but also intrigued to learn this little piece of the life history of these insects.

Anyway, the one this night, and a few moths also attracted to the lights, were signs of improving weather. So the next morning we checked the forecast and it was for a cloudless day (heavy winds still) and low sixties. We packed a lunch and for a second time made our 64-mile trip to Village Creek SP. This is the time of year skunks are on the move; we counted seven or eight road kills on the way down. All the flags we passed were straight out heading east. It was the third day this week of steady west winds, seemingly off the desert. Our yard had been water-logged all winter, but now was quickly drying out. The year it seemed was still trying to figure out whether it would be floods or drought, and I had a feeling drought was going to win.

When we got to the park we drove straight up to the high ridge trail and walked out to the best area for finding Nicocles pictus. Robber Flies aren't popular enough to have popular names, but I sort of enjoy learning all the Latin names, and the names help you keep the taxonomy straight, instead of confusing you as popular names often do. We spotted a Nicocles almost at once, about a yard up from the ground on the bud tip of a new young Sweetgum. It was much smaller, maybe 15 mm long, than we remembered the species being, though it was a male, and the males are always smaller. It flew up and came down again with a tiny bee it had just caught.

And then it performed its own special mate-finding trick. The last two segments of the abdomen from the right angle shine up like silver mirrors. This is usually concealed under their folded wings, but when they are at their twig-end post, they repeatedly drop their abdomen down, and the silver tip flashes a come-on to any female in the neighborhood. We spent some time trying to photograph them, but we were awkward I think from not having taken many pictures over the winter, and the beating wind made it almost impossible to hold them in focus and still their motion. But here are some shots that will give you an idea of what we saw.

As we stood back a little bit from the scene, we realized we were in the middle of a lek: There were three Nicocles all within a few feet of each other, all flashing away. Then they did something we had never seen before. One or another would fly out into the open pathway and hang suspended in mid air, hovering, the wings wide apart, and the spots on the dangling abdomen shining for whoever was there to see them.

That was one of our missions for coming down here accomplished.

We also were looking for a particular early grasshopper called the Mischievous Bird Grasshopper, with the Latin name Schistocerca damnifica. It sounded like the first describer of this species had had quite a time with it. That was hard for us to imagine. It was one of the Bird grasshoppers, but instead of being large and dramatically patterned, it was relatively small and drab. We were walking down the trail and had just flushed an American Bird Grasshopper which took off in its powerful flight and landed twenty feet up in a tree. Now this much smaller grasshopper hopped clumsily about two feet and hid under a leaf. That made it easy for me to pick it up so we could examine it more closely.

About the only obvious connection with the larger, gaudier Birds is the eye with its vertical bands. Nevertheless, it had a curious behavior which served to set it apart from the others. We had seen a Mischievous Bird almost in this same place at this time last year. Instead of flying or hopping away from us when we approached, it lined itself up with the bare twig it was perched on, and stuck its hind legs out to each side as if these were small twigs coming off the main twig. Here is a picture we took of it then.

It seemed clever, but a little bit amateurish. As if we should try to hide by standing next to a tree and holding our arms out and arching upwards in the shape of branches. Anyway, coming back to the present day, I let the grasshopper go, and it flew about twenty feet away and landed on a fallen log. I didn't have a nice portrait of the species for my grasshopper album, so I walked over to it to see what I could do. I took this picture of him which I thought would be quite attractive, fitting him in with the undulant grain pattern of the wood, etc., but he had been annoyed enough at me handling him that he had drooled tobacco all over his face, which spoiled the effect.

He waited patiently through all that, then, to my surprise, he began slowly spreading his hind legs out to do his twigs-off-the-branch imitation. Coming off a fallen log, it didn't seem very successful.

We had come particularly to see these two species, so we felt our trip was a success. But we also noted other signs of progress. Several butterflies were out, a Mourning Cloak, a number of "orange jobs" (either Question Mark or Eastern Comma; you can only separate them if they land and give you a look, but most of these kept flying). One finally stopped, and it was an Eastern Comma. We saw another sulphur, probably Orange Sulphur, but after all, it was almost March (I'm writing this on the 27th, but we made the trip on the 26th). And we had seen two Spring Azures, a tiny blue butterfly, famous for coming out early, even flying over snow up north. These had eclosed from their chrysalis probably that day, so they were the first butterflies brand new for the season that we had seen.

We had a final nice sighting just before we pulled out, a tiny beetle with the gory name The Twice Stabbed Lady Beetle, landed on the door of the car.

Saturday, February 25, 2012

The Camberwell Beauty

Insects living in the Temperate Zone need to find some method of surviving winter. A few strong fliers among the butterflies (e.g. Monarchs, Painted Ladies) or dragonflies (e.g. Common Green Darners, Wandering Gliders) can migrate, but these are exceptions. Bernd Heinrich with his famous "rectal thermometers for bumble bees" has demonstrated that a number of insects are warm-blooded (they use muscle-flexing to keep their internal temperature well above the ambient temperature), but these insects run into the problem that there is no food available in winter. As a kind of exception to prove the rule, I have often seen Blue-bottle Flies out and active in midwinter in sub-freezing temperature (down to 28 degrees). But these are carrion feeders, and carrion is if anything even more available in winter.

But in general insects survive winter through some form of diapause, a period of dormancy, and different insects have different strategies. In the case of insects with full metamorphosis, like butterflies, some spend the winter as eggs, some hibernate as partially grown larvae, some as chrysalises, and some as adults.

The last class is by far the smallest, fewer than a dozen in Arkansas. They are the ones you sometimes see out briefly on a warm day in midwinter, and of course they are the first ones out in spring.

Yesterday we went to Hatchie Coon Island in southeastern Craighead County, in the St. Francis Sunken Lands, a large area that sank twenty or so feet below ground level during the New Madrid earthquakes. The forecast was for the warmest day so far this year, and it was. There were high winds from the south changing to the west, intermittent clouds, and a temperature that reached 78. We noticed numbers of small crane flies out with lots of courtship in progress. Here's a photo of a pair. Note the extraordinarily long hind legs on the male.

Twice we saw adult pygmy grasshoppers, which we were particularly interested in, since the very early species might be ones we haven't seen before. But they disappeared before we could get good photos of them. Otherwise not much was going on. About 1:00 we stopped for lunch and while we were eating a Mourning Cloak landed on the dirt road in front of us. When this handsome butterfly is fresh (which was last summer) the cloak is a rich sable with a row of blue gems, and then trimmed with ermine. It is the mourning cloak of royalty. The species is found all over this country and throughout Eurasia, where it very occasionally makes it across the channel to England. There it is known as the Camberwell Beauty and is considered a prime rarity.  Cheryl's brother in England is a keen naturalist, but he has never seen one. I love sending him pictures and saying  "more of our backyard trash."

Here is the screwy life history: The species emerges from the chrysalis in the summer and if you are lucky you can catch a glimpse of it then in its fresh perfection. It tanks up on nectar or on sap dripping from injuries in trees. Then it more or less disappears from sight, estivating in the heat of summer, spending the winter behind loose bark or in a hollow tree. It reappears in the first warm days of spring, by that time so scratched and faded and tattered you hardly recognize it. Here is a summer picture followed by a picture of one of the ones we saw yesterday.

It is in that sorry state, seemingly at the end of their rope, that the males court the females. Though the roads had been empty when we arrived, now when we drove slowly down the same roads it seemed like there was a Mourning Cloak every fifty or hundred feet. These were all males, sitting on their territories. When we came up close to them we could see their tongues were out, and they were drinking up different salts from the mud of the road. These would go into the semen they gave the female, to help nourish the developing eggs. The other thing they were doing on the road was making themselves easy to see from a distance, to attract whatever females were around. Stop and think: If we are, say, a million times larger than an insect, then the insect lives in a world that is a million times larger than ours, and therefore a million times chancier for a male to find a female. This area where we were is very flat, and the bare roads make the males very visible. They further improved their odds by all appearing at a particular time: the afternoon. Another place we will begin finding butterflies right now is on hilltops. Lots of butterflies (and other insects) narrow down the odds of finding a friendly single by heading for the top of a hill. The hilltop draws up butterflies from all around to a single central spot. In the next week or so we will check some hilltops. On this particular day down on the flats we saw almost all Mourning Cloaks, but we also saw a handful of Question Marks, another butterfly that overwinters as an adult.

The surprise was, we also saw a small sulphur butterfly. In appearance (though we only saw it in flight) it was like either an Orange Sulphur or a Clouded Sulphur. Both species are quite yellow in color early in the year, and very difficult to tell apart. The Orange Sulphur is the commoner species here, but this one, with its smallish size, and pale yellow color, made me think it might be a Clouded. But the problem is, both of these go into diapause as half-grown caterpillars. That means when it begins to warm up in spring they must find an appropriate plant already leafed out so they can feed on it and complete their development as a caterpillar, then make a chrysalis, develop into a butterfly, and only then come out as an adult.

So where in the world did this one come from?

The battered and faded naturalist, after enduring a long winter, can be seen out on the very first warm days.

Monday, February 20, 2012

I knew this would happen

I've just started this blog and I'm already way behind. The reason I'm way behind is, not a whole lot is  happening.

At the top of the page I have put, as a hopeful sign, a Spring Beauty out with a tiny Sweat Bee (Lasioglossum sp.) on it, but it has mainly been wet and gloomy weather.

A week ago, we had some actual wintry weather. In the middle of the day it started snowing. It was about 34 or 35 degrees, so it didn't seem like there was much chance of it sticking. In the next hour it got harder and harder. Now you could see sleet mixed in, the snowflakes still circling, but the sleet falling straight. Snow was beginning to stay on the ground and along the tops of branches, maybe a quarter of an inch. The temperature was still above freezing. I went outside and looked closely, and it wasn't sleet exactly, it was more like icy pellets. And then it began raining.

For most of you, seeing this might be mildly interesting, but I personally was getting panicky. I've mentioned before that I belong to CoCoRaHS, part of a nationwide network that reports precipitation with close accuracy using rigid procedures. I can't just say snow is falling, I have to give the depth for a twenty-four hour period, and the water content (I have to melt a sample size of snow and see how much water remains). I have to say how much the snow has settled the next day, and how much new snow is added to it, and the new water content measure, and keep doing this every day until the snow is gone. For people in the high plains and the upper MidWest where snow is piled up all winter there is nothing to it, they are used to it, they know the whole routine and just what box to record each part in. But for us down in the MidSouth, where we only get a couple of snows a year, we can't remember any of that stuff, and we have to keep retaking our on-line training course. It doesn't say a word about icy pellets. The director of the project, in his monthly reports back to us, is very witty at our expense discussing how we non-snowbelt people panic and get everything wrong.

We heard it raining all night. That was a terrific relief, it would melt off all the snow in a minute and we would only have to report how much rain was in the gauge. When I woke up next morning, I checked the thermometer first thing, and it was still above freezing. But when I looked out the window there was snow on the ground. How could that possibly be? I went outside and checked. It wasn't snow, it was all the pellets frozen together. Now how the hell do you report that?

A couple of days ago there was the promise of sun ("some cloudiness") and at least temperatures in the fifties. It was time for a real expedition. Cheryl packed a lunch and we took off for Village Creek State Park. It's the largest state park, about an hour south of us on Crowley's Ridge near Wynne. We had a goal: the first robber fly of the season, Nicocles pictus, comes out in the second week of February, at least a month before any other robber fly. Village Creek is the best place to find them. Robber Flies are my main insect obsession. They are big hairy predatory flies that operate like falcons. That is to say, they pick a spot (the end of a twig, the top of a bush, an open area of ground with clear sky around it) to wait, and when an insect flies over, they sweep up faster than the eye can follow, grasp the insect in their muscular spiky legs, stab it with their beaks loaded with neurotoxins and digestive enzymes, carry it back to their post, and suck its juices out. They often favor wasps and bees and other robber flies as prey, all dangerous things which they attack fearlessly. How can you not love them!

Here is a picture of Nicocles, which I have downloaded from my website (which you may click on over to the right here, if you want to learn more about this very special family of insects). Admittedly Nicocles is not one of the larger members of the group (the different species run in size from about 4 mm to about 50 mm, and Nicocles is probably about 15) but it has many interesting features about it, especially the fact that you can see one in February after not having seen a robber fly since last year.

When we set out from Jonesboro it was overcast, but the promise was for sun. Sun and at least some warmth would bring Nicocles out. Now Village Creek SP is a long drive down, and when you get there it has a bad habit of building up clouds in the afternoon. I recalled reading an article by a man who was studying the behavior of a certain species of robber fly which required him to sit and watch one throughout the day. He was out during a partially cloudy day and when it was sunny the robber went about its business, but whenever a cloud covered the sun, the fly dove headfirst into the leaf litter, and didn't come out until the cloud passed.

However as we drove, the clouds broke up then disappeared. The sun shone down and the thermometer on the car went up, low fifties and climbing. Then as we entered the park the clouds came from nowhere and enclosed the sky. There were still a few breaks, so we went quickly up to a high ridge trail on the south side that was usually a dependable place for Nicocles. We walked the trail hurriedly, watching the tips of twigs, but it was cold, and the sun was going quickly. There were loud buzzing sounds all around, often the first sign of robbers, but they were all a dark species of Flower Fly (Family Syrphidae), a species which we always see early in the year. They were on the path everywhere, but it was too dark and cold to see a robber.

In fact the day was steadily getting darker and colder, so we decided to return home. The round trip would be 125 miles. Here is where you discover if you have a genuine obsession for insects. We had driven all the way down here for the purpose of seeing a 15 mm-long fly. Not a new one; one we had seen many times before. If we had seen it, the day would have been a great success. Now that we hadn't seen it, we were guiltily aware of this extension of our carbon footprint, of this quarter tank of gas expended.

To get a little gain from our trip, we decided to do some exploring. The park is huge, and terrific for insects. After years of going there we were still discovering new paths. On this day we drove clear to the northern side of the park and found a bridle path we had never taken before and walked some way along it. It was a completely different habitat, and looked very promising for later in the summer. We would be back.

Saturday, February 11, 2012

More signs

We were staying with our friends in Hot Springs Village, and spent one day driving the Forest Service roads north of the Village in the Winona WMA. In summer it's a terrific place to find uncommon insects, but this day in mid-winter it was cold and darkly overcast, and nothing was stirring, save for numerous flocks of juncos. We decided to spend most of the day driving roads new to us, noting promising looking locations we might visit again later in the year when things warmed up. Last thing in the day we stopped at Iron Springs Campground on Highway 7. A stream runs through it, and sometimes even on cold days there will be some signs of life under water. We walked along the edge of the stream in an area where during past summers we had seen darters courting, the tiny male sidling up to the female and suddenly flaring his huge brightly colored dorsal fin. But today not a fish in sight, no aquatic beetle trundling along the bottom, nothing.

But then we saw something we would normally have missed. In the past we had gone up to the water's edge to look in, but paid no attention to the shrubby vegetation we were walking through. Today, all the leaves were gone, and the bare sticks of the tall bushes around us revealed that they were in full bloom.

First we saw the alders, which of course would be expected here along the streamside, but what we had now were the tiny red female flowers, and then, hanging below them, the long dangling catkins of the male flowers. (The name "catkin," I just learned, comes from their resemblance to a cat's tail.)

The other thing that was there we didn't see for a few moments. Then we noticed a small flower, and it was as if a light turned on and we saw the bush in front of us was in full bloom, covered with small flowers, and then we saw that, except for the few alders which were on the edge of the water, all the bushes around us with their waxy aromatic space-alien flowers were this other thing: It was Vernal Witch-hazel. Here is a picture of it showing some flowers, and some buds not yet unfurled.

In this second picture you can see a seed pod from last summer. When these pods snap open, they can hurl a seed up to thirty feet. This area here had dozens of large bushes. At the right moment in summer it must have been like a war zone.

Along with these early blooming flowers, there was also the promise of a flower that wouldn't be out until summer. At our feet we could see the leaves of Cranefly Orchids (one turned over to show the purple underside). Months from now, when these leaves are long gone, the tiny insect-like flower will appear. It is so inconspicuous without the leaves to point it out, that some people put a little stake by the leaf so they will be able to locate the flower later.

Have you noticed how often very early leaves are purple underneath? One theory I have heard is that the purple is an indication of a lot of sugar in the leaf, which apparently can act as an antifreeze.

Thursday, February 2, 2012

Mystery solved by new book

We were exploring some new (to us) trails in Scatter Creek WMA in Cross County. The dirt road went through alternating woodland and grassy flats. We began noticing that the branches of young saplings we were walking past were split on the underside and partially ripped open. At first we wondered if it might be damage from browsing deer, but when we looked more closely we could see the regularity of the scarring and our speculation went to some sort of orthopter. Could a katydid do something like that? We thought that some kinds might use their ovipositors to make slits in bark to deposit their eggs. They would have to be large (the branch in the picture is perhaps an inch and a half in diameter), but some katydids are very large. But the more we looked, the more widespread the damage was. In fact it was on almost every small branch we saw over a large area. It would have to be an awful lot of katydids. It would have to be a plague of katydids. We began dropping that theory.

But what could it be? It was a mystery of nature. It was evidently a sign left by something done by a large insect on an incredibly large scale. We both realized at the same moment that the answer was waiting for us in a book we had just purchased, and the moment we got home we took the book out. It would be its first test.

The book is Tracks & Sign of Insects and Other Invertebrates, by Charley Eiseman and Noah Charney, a field guide to all the tiny footprints, burrow openings, carved hieroglyphics under the bark of dead trees and other residua left behind by insects who are no longer there. We looked in the index and found the entry "oviposition scars: cicadas" and there was the answer, the largeish superabundant insects we were looking for. We had completely forgotten the great event of last summer, the biggest, most widespread emergence we had ever seen of Thirteen-Year Periodic Cicadas. Early last summer we couldn't visit woods anywhere in the state that didn't have their persistent calling in the background. We all know the story, the broad blunt larvae with their powerful digging forelegs burrowing under the trees sucking on the juices in their roots for thirteen years before rising to the surface at a synchronized moment in all their millions to shed into adulthood for their brief moment in the sun, spending it as we hope we would, singing and mating. We have heard that they have no fright or evasion reflex, whatever wants to can walk up and gorge on them. There are so many of them all at once that their predators are quickly sated and there are still millions left to insert their eggs into slits on the underside of branches and twigs so hatching larvae can drop to the ground and dig down to the roots.

If you are an inquiring sort of person you might wonder how these insects and their Seventeen-Year cousins got started on this rather bizarre life plan. The best theory I have heard is that originally they were one-year cicadas like the other species but they were beset by a parasite which fed on their tissues. When the cicada larva crawled with the last of its strength up to the surface to try to become an adult, the parasite timed things to also be ready to emerge as an adult. Well, there is always a bit of variability, and a few cicada larvae didn't come up after the first year, but stayed underground for a second year, and when the parasite matured after one year, it was stuck underground and perished. But of course there was variability in the parasite too, and some of them waited until the second year to transform into adults and so survived. But then some cicada larvae waited until the third year, and so on, until some populations reached thirteen years, and some seventeen years, before the poor parasite gave up. This theory can't be proved, naturally, since the losing parasite no longer exists.