Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Thursday: 26 May 2011

Hidden Jewels  -  @ 04:18:09

I've mentioned before that birds around our place are fairly shy, compared to their city cousins. Even when we fed birds, only titmice and chickadees approached a comparable degree of comfort around humans. Blue jays, scarce to begin with, did not descend from the canopies to eat. Yet around and close to us we have breeding great crested flycatchers, phoebes, and as you can see here, summer tanagers.

It surprised me a little to start seeing this pair of summer tanagers keeping such a close eye on us. For the last week or two the male has stopped by in the crabapple just past the front door, to peer at me reading on the stoop before moving on to his destination.

He certainly rivals a cardinal for brilliance of color. Although the photo doesn't show it well, he sports a punk doo that ruffles up the top of his head most of the time.


Quite a dimorphy between male and female. She is brilliant in her own right.

Yesterday they spent much of the hot afternoon in the birches on the north side of the house, which is where they are in the photos above. He started it off, calling for her for a half hour before she made an appearance. Then they both started in, and binoculars revealed that her beak was filled with something. They chattered on for half an hour, in their unmelodious descending trio of chirps, before apparently giving up.


Given the date, I'm guessing they were calling fledglings to fly, unsuccessfully. They should have nested and laid eggs by a few weeks ago, here, and I don't think she'd be making an appearance in such a way if she had a nest and eggs to attend to.

There are at least another two or three pairs that I see in the woods on the other sides of the house, but these seem to have claimed the northeast side. Apparently they'll only breed once this season, though.

These are not scarlet tanagers. The photo doesn't show it, but the male definitely lacks the black wings that would give him away. It's conceivable that we might have scarlet tanagers breeding here - most of the maps do show north Georgia as being the southern extreme of their breeding range. But when I see a range line running through north Georgia I usually guess it to be delineating the north Georgia mountains from the Piedmont, where we are. Scarlet tanagers would prefer a high, and presumably cooler, elevation.


Wednesday: 25 May 2011

If You Thought It's Been Hot and Dry, You Were Right  -  @ 07:09:24

If you're in our local area, you may be interested to know that May is shaping up to enter the realm of extremes.

So far, we've had 8 days with highs 90F and above - today will certainly be the 9th. The current forecast assures of 13 such days by the end of May. On the average, May would have 2 days 90F or above, plus or minus 3. That puts us at #2 since 1948 - in 1962 there were 14 days 90F or above in May. (Daily data since 1948 from the Weatherunderground archives).



Surprisingly, we broke no high temperatures records, though we came close. And our average daily high will probably be somewhere around 84F, 3.5 degF above average. This simple average would put us at #5 since 1948, and #13 since 1920. But we did have some cool days and cooler than usual nights - this is May, not July or August, after all, and we have had largely transparent skies. Averages destroy detail.

The current rainfall total in Athens for May so far is 0.10" (0.09" here in Wolfskin). This will be the lowest amount of rainfall in May since 1920, if we get less than the same amount between now and the end of the month. In 1936, 0.21" fell, and in 1988 we had 0.41".

We do have some chance of rainfall Thursday night and Friday, but this seems to be diminishing.

Also surprisingly, not all that many fire calls, county wide. There might have been one a day - usually a brush fire from a "controlled burn" that has gotten out of control. Humidity during our hot days has generally been low, but not very often dropping below the 25% that triggers a red flag alert.

The NOAA prognosticator tells us that we'll continue to enjoy this hot dry weather here through the first week in June, but from late June on through August have an equal chance of normal temperatures and precipitation.


Sunday: 22 May 2011

Leaf Damage in Oaks and Tulip Poplars  -  @ 07:36:33
Our cool weather has come to an end - the last few days have verged on uncomfortably warm, and for the next couple of days will get up into the mid 90s, F. This is probably going to be unusual for May - a typical May will bestow 2 plus/minus 3 days of temperatures 90F or above. So far we've had five such days, but the forecast suggests at least four more through the end of the week.

The rain is a little more problematic - April was quite dry, and so far we've had only 0.09" since April 26 (when we only had 0.57"). There's a modest chance of rain toward mid- and end-week, but it doesn't look promising.

Back on May 2, Mark, in comments, noted having heard of an infestation of unusual caterpillars that were going after oak trees. I had, coincidentally, just read in the UGA student newspaper (of all places), The Red and Black, about this.

I did a survey at that time of the various populations of our major large oaks, water, white, and northern red oaks (Quercus nigra, alba, and velutina) upland to mostly red oaks at lower elevation, and noted nothing unusual.

I did, however, observe that the leaves of our tulip poplars (Liriodendron tulipifera) were sustaining an unusual amount of damage. Here's a photo of upper leaves taken May 10:



Now the tulip poplars will get very ratty along about August, but I haven't seen them like this, this early in the warm season. The damage seems to be a combination of necrosis around the edges and holes eaten inside the margins of the leaves. From what I'm seeing a week or more later, the damage is pretty severe.

On May 19, I did another survey, and noted that most of our white oaks are now showing leaves with a lot of damage. I didn't notice any such damage on northern red oaks or water oaks, our two other most abundant large Quercus species:



This damage looks different from the tulip poplar damage. The leaves have been partially or largely eaten away from the margins inward.

The oaks, at least, have now drawn, this week, the attention of the local county weekly, the Oglethorpe Echo.

This seems to be an outbreak of black-dotted brown moth (Cissusa spadix). A UGA School of Forestry professor, Kamal Gandhi, along with School of Ecology professor Jacqueline Mohan, have been looking at this apparently unique outbreak. The life cycle is not well known, but the caterpillars seem to hide in the leaf litter in the ground during the day, and journey up into the trees at night. Gandhi requests information about unusual tree damage, especially oaks, that might be related to the outbreak. As of the beginning of May, the caterpillars were confirmed in Clarke, Oglethorpe, Oconee, and Madison counties (centered, well, around Wolfskin, actually), and Barrow and Gwinnett Counties (more toward Atlanta) were of concern.

Bugguide has photos of the adult moth here. The only measurement of wingspan I find is 35 mm, a fairly modest size, so the moth is not especially large. There are no photographs of larvae, which are seen mostly at night. The Red and Black article I link to above has a photo of the larvae, and current interest in this species is due to landowners bringing in larvae.

As far as I'm able to tell, this species is a native. Two years ago I reported that we were having quite an infestation of tent caterpillars, Malacosoma americanum, also a native. That was on April 15 2009, but in 2010 (and now perhaps 2011) I've seen virtually no tent caterpillars. There is no particular moral to gain from this, other than that many insects (especially) have boom and bust cycles under normal conditions. There are certainly now examples of formerly innocuous pests that have become perennially malignant.


Saturday: 21 May 2011

Postcards from the Rapture  -  @ 06:25:26

Hmm, Glenn seems to have been called home early, during the night. They must be doing beta testing.

Now I know what you're going to say: "These photos have been doctored, Wayne. You took a picture of Glenn posing, lying on the floor, and then photoshopped him out."



OK. Here's another one, from another angle. There, you see, same thing. Convinced now?




NOTE: I was wrong yesterday - it's 6pm local time, not 6:30pm. We are sorry for any inconvenience. I haven't been so embarrassed since I was off a day for the Geminids a few years ago.

Friday: 20 May 2011

In the Event of Rapture  -  @ 08:43:09
Tomorrow does not just mark the three week point at the current Brood XIX emergence, it's also the Rapture. In case you're not aware, the Rapture starts at 6:30pm local time. That's right - it apparently begins at the International Date Line at 6:30pm local time on May 21 and moves westward each hour: earthquakes, volcanoes, assorted mayhem, and lots of wind and rain, I imagine. Probably pestilence. Sort like New Year's Day with a twist. So we'll get about 14 hours of warning, I'd guess, with the internets and all, assuming DSL holds up.

Many may imagine themselves to be on The Rapture List, but in my judgment they have made a fundamental mistake: the First Commandment to Adam was to name the beasts of the field and the birds of the air. Genesis is a little disjointed, with plot elements not very well paced or placed, but when you sort it all out, there can be no doubt.

Never thought I'd be doing this - copying/pasting bible verses!

19 So out of the ground the LORD God formed every beast of the field and every bird of the air, and brought them to the man to see what he would call them; and whatever the man called every living creature, that was its name. 20 The man gave names to all cattle, and to the birds of the air, and to every beast of the field; but for the man there was not found a helper fit for him.


It was clearly pre-Eve, and immediately post-Adam, who'd barely had a chance to yank his finger away. (It's understandable, after all, who hasn't been confused when you wake up for the First Time and you're still a little Fuzzy, and Someone is Shouting at you. And presto, there's Original Sin if there ever was one.) And so it was therefore pre-apple and that whole be fruitful thing that got us into so much trouble. It's all very clear.

And so we have it that TAXONOMISTS and SYSTEMATISTS have been doing God's Work more than anyone else, and so they are the bulk of The Rapture List, for they more than anyone else have fulfilled the First Commandment. I'm sorry for those of you who poo poo'ed the notion of names being important, and just wanted to groove with the feeling, but you should have thought ahead. Actually, it wouldn't have done any good - The List was apparently made up thousands of years ago at the beginning of the world and nothing you could have done would have changed *that*, even if you had paid attention to my gentle persuasions. That's what you get when you deal with deities, and don't sweat the small stuff.

Anyway, I thought I'd serve notice that when you wonder where Niches, Glenn, and Wayne went, well, now you know. For the rest of you, until the REAL end of the world on October 21, I'm afraid it's five months of horror beyond measure, as Mr Camping gleefully tells us, but boy is he in for a surprise tomorrow ; - )  !

*I don't know if Weakley or Radford will make the Rapture - depends on whether The List favors splitters or lumpers. Then there's that whole renaming heresy thing going for you, also. And I have no idea what to predict about the cladists, DNA or not.

**Would someone please feed the cats? Violet needs to have canned KD. Everyone else is fine with the dry CD - four 20-lb bags are in the front closet. We'll put in a good word for you.

Wednesday: 18 May 2011

Two Individuals  -  @ 06:26:41
After an early morning low of 49F, yesterday's temperatures peaked, before noon, at just a hair under 70F, and then dropped slowly to 64F. In the late morning, clouds gathered, it became completely overcast the rest of the day, and the cicadas did not call. I was able to confirm during this period that the cicadas will call above 60F, so long as there is direct sun. Below 70F (at least), cloud cover will silence them. I haven't found the upper limit to that dependence, but it's useful information for those who want to go out and find cicadas by sound.

Today the temps are supposed to peak around 72 (it's 46 right now at 6am!), and it's supposed to be partly cloudy, so perhaps I'll get a little more information on that. It really is quite remarkable to hear them calling, then the sun goes behind a cloud and they stop, then it comes out and they start back up again!

Mid afternoon, I found a lone cicada staggering on the front deck. As you can see, it has a lot of yellow, and it's missing an eye. This seemed a good opportunity to compare two individuals - this one, and the one collected and photographed by Tom and Gisela 800 feet to our northeast on May 9, and reported here.

The white background photos are Tom and Gisela's; the blue or finger photos are my discovery yesterday.


In the two photos below, I think my individual (top, click photo for larger version) must be a female M. tredecim. The ovipositor is pretty clearly present at the end of the abdomen. Body length is 3.0cm and the wings extend 1.0 cm beyond that.





M. tredecim is likely the commonest of the three species that potentially constitute Brood XIX around here. It seems to me that Tom and Gisela's individual (bottom) is most likely a male, and has not nearly the extensive yellow banding that typifies a M. tredecim.

The two alternatives are M. tredecassini and M. tredecula.





The more likely species for the darker insect is M. tredecassini. I can't tell by song, since I haven't heard individuals, but the overall hum with its drop tones sound much like the recordings I've heard of M. tredecim.




Tuesday: 17 May 2011

Current Manifestations  -  @ 06:19:23
Yesterday was quite cool - 60-65F during the daylight hours, and thick overcast after 10am. The cicadas were completely silent except on one brief occasion: they began singing at 9:30am, when the temperature was 60F and the sun had just come out for a few minutes. As soon as it went back in they went silent, even though it got slightly warmer during the course of the day.

I spent much of the day gathering anecdotal reports from various sources, and Glenn gathered some more at a bee club meeting in the evening. I've encoded a rough map distilled from our anecdotal reports, for a couple of folks who have inquired as to where to go to hear the cicadas. These would cover the observations made around May 15.

They are gleaned from a total of 16 or 17 contacts. The numbering system is 0-4, where 0 is nothing (and you might as well include all of Athens from what I've heard); 1 (blue) is occasionally hear something, have found a few casts; 2 (orange) is my local baseline - considerable song in all directions at a distance, individuals may have been observed. Glenn's descriptions follow: Level 3 (red)is sound at the level of "normal speech", flying individuals are always seen, and as for dead ones, "watch your step." I'm postulating a Level 4 not seen here: Glenn calls it "I can't hear you," "Can't open my mouth" (flying insects), and "Need a shovel."

Keep an eye on the weather - note that if it's cloudy and cool today, cicadas may not perform. If it's cool and sunny, they may sing normally.

As usual, you'll get a larger (600KB), more extensive and clearer version by clicking on the smaller(69KB) map here:



No one seems inclined to fill out the report maps at Magicicada.org. It's a rotten shame that there would be this region where people have knowledge, but won't add it to the magicada map which is quite, quite empty here. Isn't this pathetic?



So the plan, if it's not cloudy and the cicadas are singing, will be to visit these areas and areas in between over the next few days. I've downloaded a neat GPS app, which gives coordinates and allows info to be "shared," which in my case means saved to a wordpad-type app. Then *I* can legitimately add the data to the magicada map, for our area.

(I will say that it's unfortunate that such mapping efforts don't usually include an option for *zero* events noted, within such a large event as this. As we rainfall observers all know, zeroes are as important as actual occurrences. However, if you can't get people to add their exciting encounters, you certainly can't get them to add their negative observations.)


Monday: 16 May 2011

How Did They Get There?  -  @ 06:53:13
The periodical Magicicada species have several unusual characteristics, to say the least. With their 13- and 17-year life cycles, they have unusually long life spans, the vast majority of which are spent as non reproductive juveniles underground. Their emergence at the end of a given cycle is synchronous. How did cycles of any sort emerge, and why such long ones? How are they maintained?

The 13- and 17-year spans are themselves prime numbers, but the only prime numbers that have emerged as selected for. Why not non-primes? Why not higher, or lower prime numbers? Why prime numbers at all - are they just a coincidence? How do juvenile cicadas count the years?

There seem to be two main explanations for the emergence and/or maintenance of long term cycles.

1. Predator avoidance - apparently cicadas are very tasty.

A lot of predators will go after cicadas if they're available, from fungal parasites to other arthropods to a multitude of vertebrates - fish, mammals, reptiles, and birds.

This older theory, the one you're most likely to run across first, would suggest that avoidance of predators drove the selection of long cycles, to avoid annual appearance that would allow predators to synchronize their own populations with the annual appearance of tasty cicadas. The preference for prime numbers is a fine-tuning of this avoidance, where non prime cycles can be more easily matched by predator life cycles than prime numbered life cycle lengths.

Once in place genetically, synchronous emergence of large numbers of individuals would be selected for by predator satiation. Predators that had enough food would cease troubling a very large emergence of cicadas before they ran out of numbers - the rest would presumably act as the reproducing nucleus for the next generation.

You might predict that cicada populations depending on vast numbers for protection might be influenced less by individual selection, since the large numbers relieve individual attention to the usual details of predator avoidance, camoflauge, or defenses. Indeed, when compared to "annual" cicadas, periodical cicadas are surprisingly clumsy or predator foolhardy. They don't fly as well or as fast, they don't hide, they are more approachable. U. Oberdorster and PR Grant (2007) Biological Journal of the Linnean Society 90, 1–13. "Predator foolhardiness and morphological evolution in 17-year cicadas (Magicicada spp.)"

One objection to predator avoidance as a major selection force is the skepticism that predators would be particularly moved to adjust their life cycles to the rather short period of time cicadas are available during the warm season. Cicadas are only out for a month or two - any predator specialized to take advantage of this would not find itself well rewarded, even if the emergences were annual. My impression is that while predator avoidance/satiation might be a strong enough selective force in the short term, it's generally considered inadequate to explain how 13- and 17-year cycles emerged in the first place.

2. Paleoclimate - the end of the Pleistocene was a capricious killer.

Cicadas require both deciduous forests and a certain degree of soil and air temperature warmth before they can emerge and reproduce. These requirements were in short supply across the United States at the end of the Pleistocene. Much of the eastern United States would have been unsuitable during and immediately after the last ice age, which ended about 12,000 years ago.

The periodical cicada manifestations we see now must have largely arisen and spread during the current interglacial, and probably from a surviving southern population of annual cicadas. We have to presuppose that this original population of cicadas must have be very heterogeneous genetically - some with juvenile stages lasting one year, some two, and so forth.

There is a complicating factor - for about 1500 years after the "end" of the last ice age, around one in fifty years was a killing one, above ground, for cicadas - conditions were unsuitable for reproduction. RT Cox and CE Carleton (1988 ) Am. Midl. Nat. 120, 183-193. "Paleoclimatic Influences in the Evolution of Periodical Cicadas (Insecta: Homoptera: Cicadidae: Magicicada Spp.)"

These cicadas must get through 1500 years of exterminating weather occurring once every fifty years. Cicadas emerging every year would have been exterminated within fifty years. Cicadas emerging every two years would have a little better chance, since they could by chance leapfrog that one bad year, but only with a 50% chance - they would have been lasted just a little longer than the annuals. Four year periodicities only have a 0.4% chance of getting through 1500 years.

You have to get up into the 15-20 year periodicities before you can get these guys through 1500 years with a reasonable chance of survival. And when you add a few other factors (the Allee effect, for instance), cycles of prime number length turn out to be unusually stable for maintaining a cycle at a particular length. Y Tanaka, J Yoshimura, C Simon, JR Cooley, and K Tainaka (2009) PNAS 106, 8975-8979. "Allee effect in the selection for prime-numbered cycles in periodical cicadas".

So a 17-year cycle emerges as 95% probable to get a population through that 1500 year period of selection with a high probability. Surviving populations would increasingly have the 17 year periodicity. (Presumably 13-year cycles would have evolved from that.)

Why not 19-, 23-, or 29-year cycles? Well, sure, they'd also be very likely to rescue the cicadas through that 1500 year period. But as remarkably long as their life spans are, there must be *some* upper limit to how long juveniles can remain underground before they must emerge as reproductive adults.

One objection might be that that 1500 year iffy period no longer exists - why, then, would cyclic periods of 17 and 13 years be of current advantage? This may be where predator avoidance and satiation is able to maintain a stabilizing selection. Once established, the 13 and 17 year cycles are advantageous for other reasons - stragglers emerging a year before or after the main population would be snapped up because they're in such low numbers. This selects against stragglers and for the 13 or 17 year average, maintaining tightly the two cycles.

Why, too, did not a parallel sort of periodical evolution occur in the northern hemisphere Europe, or Asia, there at the limits of the ice age glaciers? Perhaps the ancestral cicada gene pool available in these locations did not include sufficient cicada longevity.

Magicada.org maintains an extensive bibliography here. I've only looked through a few of these references, so I've undoubtedly left much out that addresses evolutionary issues.



Sunday: 15 May 2011

Mapping the Periodical Cicadas  -  @ 06:32:57
This is a kind of primer, for my own purposes, for periodical cicadas, just about as fascinating an evolutionary phenomenon as there is. I should say here that there are many excellent explanations to be found on various websites, and what follows in the next three or five paragraphs may not be the best, since it is mine. I should also say that this is certainly not my area of detailed expertise, and that my explanations may be a bit mushy or imprecise, on occasion, from the point of view of someone working actively in the field. Just so we all understand that!

The insect family Cicadidae contains around 2500 species of cicadas found all over the world. As a whole, cicadas are typified as insects with very long underground juvenile stages, and relatively short adult lives during which reproduction occurs. Cicadas are at the top of the insect life cycle span, and where that is the longest it's because of those lazy underground years that the kids experience. Most species are annuals, but this just means that you see the species emerge each year. The adults that emerge may have been underground as juveniles for years, and some proportion of these juveniles emerge each year and reproduce. Around our area these are called "green dogs," among other things, and one of our most common are in the genus Tibicen. They usually emerge in mid to late summer, so that's another way they differ from the periodical cicadas.

Those are the annuals, and let us now dispense with them. There is one and only one genus, Magicicada, found only in the eastern US, that are referred to as periodicals. Periodicals emerge synchronously, in late April or early May, after long years as juveniles underground, and they emerge in huge numbers to mate and lay eggs. An egg will hatch, develop quickly into a tiny nymph which will then fall to the ground and burrow in. Over the next 13 or 17 years, it will feed on sap from root vascular tissue of hardwood trees (mostly), and grow very slowly.

These emergences infiltrate the human realm because they are accompanied by the two month long cacophony of songs of reproduction. Some like it, some don't. (As SteveK pointed out, the days of cacophony are followed by millions of dead bodies.) Sometimes it takes a hammer to hit some folks over the head, and that's why we love hammers.

Most years, somewhere in the eastern US, there will be an emergence that is called a brood. This brood will be a member of the 13-year or 17-year brood groups. Broods are identified by roman numeral. If Brood X, the Great Eastern Brood, emerged in 2004 (which it did), then Brood XI would emerge in 2005 (which it didn't since it appears to be extinct).

There are theoretically seventeen 17-year broods, which would be numbered Brood I-XVII, if there were a brood each year. There isn't a brood for each year, though, either because there may never have been a brood that year (Broods XII, XV, XVI, and XVII) or because a brood became extinct (Brood XI, which hasn't been seen in and around CT/MA since 1954). 17-year broods are more common (roughly) in the northern half of the US.

And there are theoretically thirteen 13-year broods, but even fewer years are occupied by these. Only Broods XIX, XXII, and XXIII are known to exist. Brood XXI, in and around Tallahassee FL, hasn't been seen since 1870, failing to appear in ten consecutive cycles. 13-year broods are more southern in location, although there is overlap with the 17-year broods.

It is the 13-year Brood XIX that made its appearance this year. This is the Great Southern Brood, last seen in 1998 and not to be seen again until 2024. It's "Great," one of the largest, because its members occupy a huge part of the country.

Here is a map of the range of 13-year Brood XIX. It appears in a large sweeping arc from central NC through much of GA and AL (also MS and northern LA), and then north through AR, MO, and part of TN,IL, and KY.

The maps I'm presenting here are modifications of those appearing at the Magicicada website, with their permission. John Cooley, who is working extensively on mapping and especially this year, reminds me that these are only rough maps and that appearances within the rough boundaries are often patchy. There are more detailed historical maps given along with the versions here, and you can find those maps for any given brood here.

I might add that the only reason these maps are possible in any detail is because people make observations and submit them. You can (and should!) do that here. You can see the growing number of observations being made right now for Brood XIX here. As the season progresses there will be more and more observations in the MO/IL areas.


If you go to the Brood XIX mapping page, you'll see the above map (consisting only of positive records as of Dec 2010), and you'll also see another historical map obtained from 1923, 1988, and others. It's more detailed, but the geographical ranges of these broods do change from emergence to emergence.

Here is a composite of all three 13-year broods, along with the last time and the next time they'll appear.



Brood XXII is a very tiny one (as was extinct Brood XXI), centered around northeastern LA and southwest MS. If only they appeared in the same year, Brood XXII, in blue green, would have the potential to mate with Brood XXIII, in red, but they have been temporally reproductively isolated by a year. Similarly much of Brood XXII (red) might have been able to mate with Brood XIX this year, except that four years separates the two emergences.

It is thought that the 13-year broods have evolved from the 17-year broods, but the evolution of periodical cicadas will have to wait.

Here is a composite of the twelve known and existing 17-year broods (clicking on the image gives you a large version in a new page).



You can see that these tend to fall more northerly than the 13-year broods, although there is some overlap. Remarkably, few of the 17-year broods overlap with each other. There are some very tiny emergences - Brood VII in western NY, for instance, or Brood VIII in southwestern PA. The largest emergence, which was last seen in 2004 and won't emerge again until 2021, is Brood X, the Great Eastern Brood. It seems to have broken up into three main geographical regions - the one around Indiana, the one at the TN-NC border, and the one around Washington DC. This brood is isolated not only in time, but also in space.

So we see that by definition, the 13-year broods are isolated temporally from each other, and the 17-year broods are also isolated from each other.

What about the co-emergence of a 13 and a 17-year brood? For any given pair, this is something that happens only every 221 years (17x13). Here is a rough depiction of the areas where our current Brood XIX might co-emerge with some of the 17-year broods (clicking on the image gives you a large version in a new page).



I've removed two of the 17-year brood panels, and have placed the 13-year Brood XIX panel there. The lines connect rough geographical regions where, in the right year, there might be co-emergence with a 17-year brood.

This year, there were no possibilities for co-emergence - no 17-year brood emerged this year. In 2015, Broods IV and XXIII will co-emerge, but they are so far away from each other that no mating will be possible. In this figure, it is particularly likely that Brood X and Brood XIX could co-emerge in two places. In extreme northeast GA, there is the possibility, but it will not occur until 2089. Also in that year, there is the possibility that matings could occur between X and XIX in the area where KY, IL, and IN come together. I mention that one because it last happened in 1868, and there have been detailed observations made in the area in the years following that potential event.

I'll also point out that Brood XIX has a good possibility of co-emerging with Brood XIV, and again it's in that same KY/IL/IN area, as well as in central TN. This happened last in 1855, and it won't happen again until the tricentennial celebration in 2076.

So what happens when a 13-year brood co-emerges with a 17-year brood?

Here we have to get into the fact that there are three 17-year species (M. cassini, M. septendecim, and M. septendecula), and four 13-year species (M. tredecassini, M. tredecim, M. tredecula, and the newly discovered M. neotredecim). These presumably each have their own ranges within the overall range, but often emerge all together in many locations.

The biological species concept would rule that they can't interbreed, but the BSC is a simplistic thing. Closely related species may well hybridize. With the 17-year group of three, the species have been emerging together many times and sort themselves out by song - presumably hybridizations are rare. And so it is within the 13-year group. But it is likely that there could be confusion when co-emergence of 17- and 13-year groups occurs, and then we have the opportunity to try to figure out the genetics of the cicada emergence clock.

And that's what was done following the Brood XIX and Brood X co-emergence in 1868. And we should look at that, but not here or now. Here is a first-page presentation of a 1991 paper that examined this, if you just can't wait. (Somewhere I ran across a more recent paper that was available in full, and failed to bookmark it. I have to find it again.)



Saturday: 14 May 2011

Cooling  -  @ 11:25:37
We've had a break in the hot weather, with some waves coming through last night, along with the teensiest amount of rain. It's only 70F right now, 10-15F below what we've had over the past week at this time of day. The cooling trend continues through Monday, at least, and highs are not expected to climb above 80F until Thursday or Friday.

That's all very nice, but the cicadas are not happy. For the first time in two weeks, they're declining to serenade us. They started in this morning around 8am, rather strongly, but they're very quiet now - whether because of the cool or the extensive cloud cover, they're probably going to pout for the next few days.

So it might not be the best time to go looking for them.

UPDATE - Ha. The temperature had actually fallen two degrees by noon, to 68F, but as soon as the cloud cover began (temporarily) breaking up, the cicadas started back up.

Friday: 13 May 2011

Send Your Cicada Cards and Letters In!  -  @ 12:02:25
I know we're going heavy on the cicada posts, but that's what's happening around here. It's my first cicada emergence, so I'm a little excited - truth be told, I'm flabbergasted. In 2004 and 2008 there was talk of an emergence (unrelated to this one), and I paid attention, but could never convince myself that anything was happening. The reason was that it was happening considerably north of us, and we weren't involved here in Wolfskin. Now I know what it sounds like.

This one is an Event, and a great one. This is Brood XIX, the Great Southern Brood, our only brood around here, and we're a part of it. We haven't had it in this area since 1998 and we won't hear it again until 2024 - it emerges only every 13 years.

Wherever you are, but especially if you're in the Athens area, take a few minutes and record your observations at the Magicicada website. It's the top link on the right sidebar. You don't have to know everything - mainly your location and the date are the important pieces of information. Anything else is icing. There are other websites keeping track - magicicada seems the most robust and prompt to update. How cool is that?

You can see the ongoing map of observations developing here.

As I zoom into that map around Athens, I note that the current majority of local observations are east and south of Athens, just by a few miles. Athens proper? Virtually nothing. Atlanta proper is curiously devoid of observations.

Is this real or is it due to a lack of observers? If you're hearing them, you'll know it. It's unmistakeable, even if it isn't in the tree over your head. The sound will go on and on all day long. Whether you love them or hate them, take a few minutes.

Me, I'm thoroughly enjoying hearing them start up in the early morning. It's an astonishing thing, this dawn to dusk extravaganza, completely outside my experience. I sit on the back deck with my jaw continually dropped and just take it in - this relaxing but all present hum, interspersed with some very odd but frequent drop tones. It fills the air, and it gets louder day by day. I can't imagine objecting to it - it's not strident, it's not shrill, BUT.

Last week I mentioned it to someone in Athens. No, he hadn't heard it, but then he's had his air conditioner on since March, and doesn't go outside during most of the week except to get to and from his car. When he asked if they would be making noise at night, and I said, no, just during the day, he said, "good." I think he does venture outdoors on the weekend and didn't want that interfered with. It must have been that, because he keeps his air conditioning on at night too.

Yeah, BUT. Come on. Even if you hate them, send your observations in, at least once.


Wednesday: 11 May 2011

The Twelve Days of Brood XIX  -  @ 07:40:05
It's been getting steadily (and unusually) warmer each day for the last week, and today may mercifully peak in the mid 90s.

I'll direct you first to the previous post comments, which are interesting. I'll be implementing some of Dale's suggestions.

Dale has requested information as to where to go to hear the cicadas. Apparently they're not (yet?) making an appearance in Athens proper. The magicicada brood XIX map confirms this - in our local area the reports are coming in from the east of Athens. You can leave a comment for Dale and others who might want to find a local concentration, or I can relay one to him.

There are at least two places you can add to a Brood XIX database and see the results on a map. So far I've found magicicada to be prolific and helpful, and the right sidebar has the links to make reports and view the map. There is also Massachusetts Cicadas.

Yesterday I had taken my binoculars with me and scanned the trees. Don't laugh now, but I did spot this apparent cast about twenty feet up in a large water oak. Scanning through the rest of the photograph, I think I discern a number of others, but will have to look again more closely today.



Tom and Gisela took several very good documentary photos of an individual discovered May 9. The thumbnails open up to a larger photo on a new page:



I was hoping that their submission of the observation to insects@uga.edu would net us an identification - the photos are certainly good enough. There was a reply but it was just a thank you as I got a week ago. One way street, it seems.

From the photos and discussions on identifying the three major 13-year species we have here, I would reject Magicicada tredecim on the basis of the dark abdomen. That species has an almost entirely yellow abdomen. However it is the one whose recorded sound is most like what we hear.

The other two species have dark abdomens, with either distinct yellow banding (the rarer M. tredecula), or no banding or less distinct yellow banding (M. tredecassini). I guess it depends on what you call distinct or less distinct.

However, these are the easy identifiers for non experts like me. I'm sure there is much variation and overlap, and that the real keys use anatomical parts that I know nothing about!

Bugguide doesn't have many 13-year species photos, and none of M. tredecula, so I hope to submit to them in the next few days (or find that someone else has). Bugguide is always helpful, terse, but someone always pays attention - no one way street there!

I learned a few things on my walk yesterday. Besides confirming the odd phenomenon of never quite being able to reach the wall of sound apparently just a few hundreds of feet away, I learned that there's no change after sitting or standing motionlessly for a lengthy period of time. I confirmed that there just aren't any emergences in the lower elevations. I walked down SBS Creek, and then a half mile down Goulding Creek. The background hum can be heard, but it is very distant and seems clearly to come from higher elevations well away from the creeks.

I think the background hum has become noticeably louder over the twelve days since I first noted it April 29. It has also become more heterogeneous - that is, it seems I can hear it as more pronounced in one direction than in another. On my walk I think I detected at least two concentrated directions different from each other and from the other concentration that seems to come from our neighbors' location.

It seems that we have at last another month, perhaps two, of developing events.



Sunday: 8 May 2011

Cicadas Ten Days In  -  @ 08:51:55
The cicadas have been hard at work for the last ten days now. I thought by now the phenomenon of their distant background hum would have developed as more emerged, but it's remained remarkably even. Perhaps a little louder in the last two or three days.

For whatever reason, I have not been able to locate any specific aggregations of the cicadas whose persistent background hum has permeated the daytime hours. The sound is all around, all the time, and with some variation, uniformly present. But there has not yet been a point where I could point to a tree close by and say, "There's a population," or, "There's a single individual."

Yesterday, for instance, I set out southward toward what sounded like a distant source. The chorus seemed to get a little louder as I got about 500 feet toward it, and then seemed to come from my left, toward the southeast. This would have placed it in a pinier, upper elevation. I marked that as a possibility and then went down to the creek and up the other side, to the west.

In the long hollow that has been carved out by the creek I could hear virtually nothing. At present they don't seem to be populating the lower creekside elevations. After walking down the ridge northward to Goulding Creek I returned to the early southeastern elevation where the sound had seemed the loudest.

Again, there was no single source. I could walk toward the perimeter of sound, but when I got there it was just as far away as it had been. I could backtrack and try a different direction, and get a similar result.

I found it helped somewhat to cup my ears with palms facing forward. The intensity of sound improved quite a bit and was better tuned to the direction I was facing. When I did this, I think I could detect a faint hum high in the trees above and immediately around me.

I think it's a matter of not seeing the trees for forest. The trees are all around me, but are practically invisible. The forest is easy to see in the distance.

So if that's true, the cicadas are practically everywhere, including close by, but I'm not making out individual songs, just the conglomerate chorus. If so, then they must be quite numerous indeed!

I've found a few contradictory hints. There is a statement that the source of sound can be hard to locate. It's noted that some of the sound consists of frequencies so high that we can't hear them (and that goes double for me, these days). In that case, only the lower frequencies are able to travel the distance. But there are also contradictory statements that individuals can be very very loud, in which case it seems like I'd be able to locate them easily.

We still have some weeks, maybe up to two months, before this emergence is over. Maybe I'm just premature, and the main phenomenon is only about to start, with individuals everywhere close by and very clearly so. But for the moment it seems like they're individually very quiet, they're everywhere, and it's only at a distance that I can detect them en mass.

Note: Using the periodical magicicada database page, there are only six entries for Brood XIX in Georgia, and none of these is for the last emergence, 1998. Two entries are for the species Magicicada tredecassini and two are for M. tredecim, all 1985, so two emergences ago. Two are unknown (1959, so four emergences ago!). There are many more records for the 17-year periodicals, but these are north of our area and for 2000 and 2004 - they don't apply.

My guess is that UGA Entomology would really like photographs of specimens collected, for identification. From what I've seen of taxonomy, it would be especially helpful to have the abdomen (bottom half) of a specimen photographed - there are banding patterns along the "belly" that help to identify. They're also interested in casts, the remains of exoskeletons after shedding. UGA Entomology email address.



Saturday: 7 May 2011

The Month of April  -  @ 08:13:38
It's The Month of April, Number 63 in a series. April was warm, considerably warmer than usual. And there were tornadoes. A lot of tornadoes.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center.



Much of the West cooled back down in April, after a warm March. The northern Midwest was colder than normal, continuing that trend from February. Much of the Southeast continued warmer than average, as it has done since February.

If you click on that image, you'll get the maximum and minimum temperature anomalies. Once again, as in March, the maximum highs were lower than normal, especially in the West, while the minimum lows were higher than normal in comparison. We're not happy with this trend, for while it keeps the days from getting blistering hot, last year it also resulted in high humidity and misery.

We find the National Weather Service Climate Prediction Center's precipitation plots here.

Rain was normal to considerably above normal, except in the deepest south from west to east. The deep green of the eastern third of the country reflected in the widespread flooding that continues in May.




For Athens:

Here is a plot of our temperature swings in April, along with precipitation amounts as experienced in Wolfskin:



Rain was infrequent and widely interspersed. We ended up here in Wolfskin with 2.90" rain, beating out the Athens official 2.28", but still coming in lower than the average 3.35".

Here is my plot of high temperatures for the month of April in Athens. As usual, the black dots are for the years 1990-2009 (black dots), 2011 (green line), and 2010 (red line).



Our high temperatures were somewhat below average only for a few days during April, and neared record highs once or twice. There were 8 days more than one standard deviation above the norm (4.7 days normal), and only 1 night more than one standard deviation below normal (5.5 nights is normal). We were distinctly warmer by day and night count.

The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 20 years, the vast river of peach shows the standard deviation.

We didn't quite make it to the average rainfall, in April, but the large amount of rain in March means we're not really hurting as yet.



The neat prognosticator was right in its prognostication for a warmer April. Our local area is predicted to be slightly cooler and wetter for the next month. After that, nothing but normal for the next three months, for some definition of normal.

ENSO stuff:

The ENSO PDF update at this page still chokes on download - wish the Climate Prediction Center at NWS would get that fixed!

La Niña is now in decline, after a nearly year-long manifestation, and normal ENSO conditions are expected by June, just in time for hurricane season! You might recall that La Niña conditions tend to suppress hurricane formation in the North Atlantic, and now they're going away.

NOAA's Monthly State of the Climate product for March is now up. April should be appearing soon, and we'll have a thorough discussion of the extreme tornado outbreaks (which also occurred in March, although at a lower number). Detailed explanations for weather events occurring during whatever month is current can be found for the several sections of the US under the National Overview. There are many interesting weather- and climate-related items to be found here.



Tuesday: 3 May 2011

More on the Cicadas  -  @ 09:14:54
Here's a very nice photo of a Magicicada (with the red eyes) that Tom and Gisela, our neighbors, sent me after yesterday's post. Gisela, as I, had noted the all-day hum, and Tom confirmed the answer to the mystery that our *other* neighbors, Jeff and Phyllis, had provided to Glenn. Are we not lucky in our neighbors? Thanks for the photograph!



As Gisela noted, I too felt a lot better after finding it wasn't some invasive machinery. Suddenly the all-day hum sounds sweet - it started up just a bit ago.

One of the things that puzzled me as I tried to locate the source by driving around was that there was no consistent directionality - another was that in no particular location was the sound especially louder than in any other. I'm guessing that what we've been hearing, now for the fifth day, is the tip of the iceberg, a few local emergences, perhaps the early emergers. In the next month we may experience quite a cacophany as the major population emerges everywhere.

Dale mentioned in comments yesterday the magicicada website, which opens up to the Brood XIX page for now. I haven't found the data entry portion of the website yet. There is a lot of interesting stuff there now, including that a new species of 13-year periodical was discovered in 1998 - with the three that were currently known, that makes four (the new one is found more in the midwest, not here). Seventeen-year periodicals tend to be more northern; 13-year periodicals more southern.

These periodicals are interesting because of their reproductive isolation - to them, nothing exists outside of available mates when they emerge. There are species in both the 17-year and 13-year species that overlap, but they'll only meet each other every 13x17= 221 years. I don't know if there are special parties planned, but I imagine that evolutionary biologists consider this to be a very interesting event.

We have cicadas every year, more or less, but these are the annuals that emerge most likely each year, and in much smaller numbers. They're usually not the Magicicada species, but some other. Here, just about six years ago, I caught one such annual emerging - note that there are no red eyes, and that I had at least an idea that it was likely of the genus Tibicen.

And here I noted an interesting report that these mass emergences (millions of dead individuals, within short order) mean a huge influx of nitrogen into the soil around the trees that provided the fodder for the insects in the first place.

It's interesting that we humans are so afixed to the idea of childhood being merely a preface to a much longer adulthood that we tend to forget that it's not done that way a lot of the time. For periodical cicadas, the childhood is long, rich, and is spent under the ground sipping nectar from tree roots. The adult experience is short and brutal.

Finally, cicadas don't make noise at night. I'd noted that the background hum of the last few days started up soon after dawn and ended before the sun went down. This seems to be correct.



Monday: 2 May 2011

Welcome Back  -  @ 07:52:59
All day Friday (April 29) I was aware of this background hum in the air. It sounded like a band saw operated at a distance, coming from the north or northwest. Or a drill, or perhaps like the end noise in an old dialup modem internet connection. In the back of my mind was a *sawmill*, and in our area we have had a sawmill operating, some years back, and so that was a little alarming. The sawmill was miserable, it would start up at dawn and operate until dusk, and that was also the extent of this background noise (although much less miserable). Around here you get testy when a plane flies over, for otherwise there's little noise at all.

On Saturday I took a little road trip encompassing around 25 square miles, stopping here and there to see if I could pinpoint the source of the sound. It was evident at Wolfskin Fire Station, I couldn't detect it at Black Snake Road and Wolfskin, but as I drove up Black Snake toward Old Edwards Road it became noticeable again. At home, it seemed to be louder than anywhere else, but sometimes it came from the north, sometimes from the south, and sometimes from the west. I attributed this to wind - the noise, though noticeable and somewhat high pitched, was subtle enough that a couple of folks I asked said they hadn't noticed it. (How can you not notice it, I screamed in frustration, but kept it to myself.)

But Glenn had noticed it, independently, and on Sunday he took his own road trip, and ran into Phyllis and Jeff Jackson, our local wildlife biologist.

It turns out to be Cicada Brood XIX, emerging after burrowing away in 1998. Each year we have annual cicadas, and I always see a few of these, but they emerge in later summer, rather than late spring as these have. Apparently they'll be around for a couple of months. Thanks to Phyllis and Jeff for solving the mystery.

If you're in the southeast, and have some definite data to offer, send it here. The email address is at the bottom of the page. They're especially interested in any specimens or casts that you can send, as they try to track these periodic cicadas.

We're actually at a southeastern margin of Brood XIX of the 13-year cicadas. The population extends from the Mississippi from most of Missouri south, and eastward toward the Atlantic, but generally coats the southeast except Florida - anyone can play. I'm sure it would be of interest to hear of reports from the southern half of Georgia, and extreme eastern Carolinas, as well as along the mainland Gulf Coast. The map at Cicada Mania will show you what I mean.

I'll be trying to get photos and/or specimens, now that I know I'm not hunting sawmills. Very cool!


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