30 June 2009

Depth of field, f-numbers and diffraction (or how to take a rotten photograph)

In Handbook for Scientific Photography (1977), Alfred A. Blaker wrote:

As the substage diaphragm is closed, the depth of field increases (as when you close the diaphragm of your camera lens)...However, diffraction of light by the edge of the diaphragm increasingly impairs the image resolution until the image becomes "rotten."
He was explaining how to take pictures thru a microscope using a camera back and the substage diaphragm he was referring to is the one under the stage of a microscope. One encounters a similar diffraction effect when using a camera with a lens to take closeup* pictures. Blaker explained this in another book, Field Photography (1976):
...at significant magnifications the choice of f-number is...nearly always a matter for compromise between depth of field needs and the resolution of fine detail in the image. At very small apertures, diffraction of light at the diaphragm edge reduces resolution.
The bottom line is that the smallest aperture will give you the greatest depth of field, but not the best resolution†.

Here are some tests I did with my Olympus 35 mm Zuiko lens on Olympus E-500. In this case, the object was a flat wood surface and so the depth of field was not an issue. Notice the decrease in sharpness as I increased the f-stop (decreased the aperture diameter).

Click on the image to view a bigger version. These are unretouched images. Some image quality was lost because I had to compress the composite picture before I could post it here.

The decrease in sharpness going from f5.6 to f11 is almost not noticeable. Even f14 would be acceptable for some purposes. But ordinarily, I avoid the apertures above f14.

Here is another example; shots of a flower bud of trumpet vine at f5.6 and f22, again with the 35 mm lens. There is a definite loss of resolution at f22.


But now let's compare the overall images.

At f5.6 with diffused sunnlight:


And at f22 with flash light:


The one at f22 has a much wider depth of field and the overall loss of resolution due to diffraction is not noticeable at this magnification. Therefore, we follow Blaker's advice and compromise and chose between depth of field and resolution. If we want a wide depth of field despite the loss of overall sharpness, we decrease the aperture; if we want a sharp focal point amidst blurry surroundings, we increase the aperture. How you take a picture depends on what you want the picture to look like and what you will do with it. In many cases, there is no right or wrong photograph as long as the image is not too rotten.

*Blaker's definitions of closeup photography as photography at image magnifications of actual size or less and photomacrography as photography at image magnifications greater than actual size are arbitrary and pointless.
†Don't confuse this with the pixel resolution of a digital camera.

29 June 2009

Snail Poster Museum Official Hiking Laboratory

Or, official hiking shoe museum garden path snail poster. Or, cat fortune house laboratory hiking shoe.

Today’s temperate silliness has been inspired by a webpage by Charles H. Bennett. As Bennett notes, English speakers can create arbitarily long and yet meaningful chains of nouns even when starting from just a handful of appropriate words. Bennett gives an example of 2 noun loops of 5-4 words joined in a figure 8. Here is my example of 3 joined noun loops of 5-2-5 words.


You can start at any word and go in either direction to obtain a meaningful sentence of any number of words. Admittedly, some sentences may be a bit more meaningful than others, but none is grammatically wrong. Note that the word official, both a noun and an adjective, adds more variety to the endless possibilities.

Cat hiking shoe museum poster snail.

Official hiking laboratory house fortune cat hiking shoe museum garden path snail poster museum official hiking laboratory house fortune cat hiking official museum poster snail path garden...

28 June 2009

Grazing slugs and the evidence they leave behind

The northwest wall of the house receives sunlight filtered by trees and bushes and thus remains wet longer than the more southerly sides; it is a perfect habitat for cyanobacteria (blue-green algae). If it weren't for the resident slugs, a thick jungle of microscopic proportions would long have developed on the siding.

Slugs love the green stuff and on warm, humid days come out to graze on it. Here is an Arion subfuscus with its feeding track behind it.


There are a variety of tracks on the wall. Some are more elaborate than others. I suspect different species are involved.


This one reveals the marks of the individual teeth of the radula that does the scraping.


I am curious to know if I can tell the species apart from their feeding tracks. Updates will be posted.

26 June 2009

Weight lifting snails

Anyone who has tried to pick up a snail crawling on a smooth surface like a sidewalk or glass may have noticed that snails can have quite a tenacious grip. One way to measure how strongly a snail can hold onto a surface is to measure how much weight the snail can lift.

To collect some relevant data, I put together a crude apparatus consisting of a small plastic bottle taped to 2 glass microscope slides. I can increase the weight of the apparatus by adding objects, usually coins, into the bottle. The snail is placed on the upper slide. After it attaches its foot on the glass, I hold its shell and lift it up, at the same time starting a stopwatch. I selected 5 seconds as an arbitrary minimum time necessary for a lift to count as successful.

This Cepaea nemoralis carried, in addition to the apparatus itself, 3 quarters and 1 dime, or a total of 41.3 grams for 39 seconds.


That weight will be more meaningful once I express it in relation to the surface area of the snail's foot. I haven't had a chance to do that.

Keep in mind that a snail does not not actually hold onto a surface using muscle power; its grip results mainly from the functioning of the sole of its foot like a sucker. Parker* wrote in 1911:
As means of attachment snails secrete a bed of mucus, and use the foot as a sucker. Both methods are commonly employed by the same species, but in a given form one method is usually developed much in excess of the other. For instance, in Helix pomatia, Limax maximus, and other allied species, the moist surface of the expanded foot will stick with some tenacity to glass. But if such an animal be allowed to creep its length over a glass surface and thus spread a bed of mucus on which it can rest, it will be found to have multiplied the strength of its attachment many times. The mucus adheres to the glass and the surface of the foot to the mucus very much more powerfully than the foot alone can adhere to the glass.
I have noticed it is somewhat difficult to obtain reproducible results. There may be some habituation involved. If the snails are picked up too frequently, they appear to start letting go off the surface more easily.

*G. H. Parker. 1911. The mechanism of locomotion in gastropods. Journal of Morphology, 22:155-170. pdf

25 June 2009

Catbird in the backyard with something in its beak

I have been seeing a catbird* (Dumetella carolinensis) in the backyard. There must be a nearby nest in the vicinity close to the house†. Their name comes from the distinctive cry uttered with an open mouth as in the picture below. It is supposed to sound like a meow, but to me, it sounds more like a long, high-pitched me.


The funny thing was every time this bird flipped its tail down, it would dip in the bird bath. But, otherwise, I did not see the bird enter the water.

When the tail is lifted up, the reddish coverts under the tail become visible (according to the books, they are "chestnut" colored). There must be some evolutionary significance to their color and display.


At one point during this photo session, I saw the bird with something in its beak. But I just can't tell what it was. What do catbirds usually eat?


*The full name is gray catbird, although neither of my bird books lists catbirds of any other color.
That was an exercise in redundancy.

24 June 2009

Marissa confronts Mittens (from behind a screen)


Remember Mr. Mittens, one of our neighbors' cat? He is still around and he still comes to our door whenever he wants to go in his house. The other morning he was on our porch again, hoping we would walk him him over to his house and let him in, something we don't do when his owners are home.

Marissa happened to be sitting by the kitchen window and looking outside. The 2 cats watched each other for a while. There was some growling. That's when I lowered the window to prevent anyone attempting to pass thru the screen. Luckily, cats haven't figured out how to tunnel across barriers a la electrons.

23 June 2009

Melongena corona dives

Back in April when I was in Florida, I did some simple seashore experiments to investigate the behavior of the common intertidal snail Melongena corona. At low tide the snails usually bury themselves in the wet sand. My experiments consisted of removing the snails from their holes, placing them elsewhere on the sand or on rocks and then watching them. Here is one that I transplanted on a flat, wet rock surrounded by water.


A few minutes later the snail came out of its shell, slowly crawled to the edge of the rock and...


As usual, the video was made by stitching together sequential shots.

22 June 2009

Bipalium adventitium — Part 1

And now for something completely different: the land planarian Bipalium adventitium.


I found this critter a few weeks ago in the park near my house. As usual, I was looking for slugs and snails and there was this planarian crawling around the roots of a tree.

The fully stretched animal—they have very flexible bodies—was ~8 cm long.

Although Libbie Hyman described this species using the specimens collected in Pasadena, California (Hyman, 1943; pdf), it is believed to have been introduced to North America originally somewhere from eastern Asia. Here are the 3 exotic Bipalium species found in the U.S.

From Ducey et al. 2007. Southeastern Naturalist 6:449.

Bipalium adventitium preys on earthworms. Mine ate one earthworm I had put in its container, but I wasn't around to take its pictures during the process. Subsequently, it produced 3 egg cocoons. If it were a native species, I would have released it back into the wild. But, and despite the fact that it is more or less a naturalized alien, I decided that the best thing to do was to preserve it in alcohol for posterity.

Continues in Part 2.

21 June 2009

Nest sharing birds

This is a continuation of Friday's post about a large stork nest in Turkey. At the end of that post I noted that there were many small birds congregated around the storks' nest. The reader Tristram Brelstaff, who writes the blog Life and Opinions, asked in his comment if the little birds were nesting in the underside of the storks' nest. After I re-examined the original photos, I realized that that was indeed what was going on.

Here is the evidence. First, another picture of the storks in their nest. The red arrow on the left is pointing at one of the small birds. I suspect it is either some sort of sparrow or a swallow, perhaps a sand martin (bank swallow, Riparia riparia).


The green and yellow arrows are pointing at additional individuals. That those are birds is indicated by the yellow arrow. Look at it closely. Now look at the same spot in the next picture. The object in the hole is missing.


The blue arrows are pointing at the holes tunneling into the storks' nest. There are several others. They all appear to be bird nests. What we have here is a giant communal nest. My sister has remarked: "Yes, they live in an apartment building. The storks are in the penthouse".

19 June 2009

More white stork pictures from Turkey


My sister, whose stay in Turkey since last September is about to end, sent these stork pictures earlier today. She took them on the way to the city of Aydin (yes, the city named after me).


As I mentioned in this post, the white storks (Ciconia ciconia) get special treatment in Turkey. They are almost never harassed and their nests are left alone even if they reach an enormous size like the one in these pictures. One wishes that all other wild animals received the same respect.

I can't tell what those small birds are, but they seem to be attracted to the storks' nest. (See the follow-up post for more.)


Previous bird pictures from Turkey also sent by my sister are here and here.

18 June 2009

James Barbut and his mating slugs

Free access to old books on the Internet (primarily thru Google Books, the Internet Archive and the Biodiversity Heritage Library) has saved me not only many trips to libraries, but also money and time I would have otherwise spent at photocopy machines.

James Barbut was a British painter and naturalist who was active in the 1780s; he published 2 books, one on insects and the other on Vermes or worms, which, back then, included all other invertebrates.

That's more or less everything we know about Barbut.

A little more than a year ago, while searching Google Books for the occurrences of the name of the slug Limax maximus, I discovered a full copy of Barbut's worm book* The genera Vermium exemplified by various specimens of the animals contained in the orders of the Intestina et Mollusca Linnaei. In his book, Barbut had a few pages of information on the 4 slug species he knew of, including a brief but surprisingly accurate explanation of how they mate. As I was reading that section, it dawned on me that Barbut's account was one of the earliest published descriptions of the aerial mating of Limax maximus.

Subsequenly, I turned all of that into a short paper that came out in the March 2009 issue of Mollusc World, the magazine of the Conchological Society of Great Britain and Ireland. My copy arrived only a few days ago.

A pdf version of the paper is here.

Barbut's Limax maximus.

I will appreciate receiving any further biographical information on James Barbut.

*An earlier edition is available at the Biodiversity Heritage Library.

17 June 2009

3 books from the bookstore that sells used books

Yesterday and today I attended a workshop at the U.S. Pharmacopeia in Rockville, Maryland. During one of the lunch breaks, I took a walk to the nearby Second Story Books. Bookstores that sell old books for profit tend to overprice their wares, often remaining oblivious to the fact that many 19th and early 20th century books are now available for free either on Google Books or the Internet Archive. Luckily, in this store everything was 25% off and I ended up getting 3 books at quite reasonable prices.


Julian Huxley's classic Problems of Relative Growth was originally published in 1932. I had already photocopied some pages from it. Now I have the entire thing, albeit it's a 1972 reprint. That one was $2.25. In Search of Nautilus by Peter Ward (1988) looked interesting and the price, $4.5, was good.

I bought the 3rd book, The Orientation of Animals by Fraenkel & Gunn (1961), for $3, mainly to read the chapter titled Variation in behaviour. I have lately been intrigued by certain variations in the behaviors of snails and slugs and thought that the ideas in this book could provide some relevant background. On the other hand, they are likely to be obsolete. But, still...

16 June 2009

Probably a five-lined skink...

...but I am not sure. I photographed this creature along the Billy Goat Trail last Saturday. It was probably at least ~20 cm long.


It is either the common five-lined skink (Eumeces fasciatus) or the broad-headed skink (Eumeces laticeps). According to Amphibians and Reptiles of Delmarva (White & White, 2002), the 2 species may be distinguished by their numbers of certain facial scales.

Figure 17 from Amphibians and Reptiles of Delmarva.

This particular individual had 4 upper labial scales, which would make it a five-lined skink. But only 1 postlabial scale is visible in the photo. So, either the 2nd postlabial isn't visible or this is an unusual specimen. Based on its coloration, it's a male (of either species).


Yes, I am surprised too that I could get so close to it before it finally ran away.

15 June 2009

From the laws of the cats

This is my Man. I am not afraid of him.

He is very strong for he eats a great deal; he is an Eater of All Things. What are you eating? Give me some!

He is not beautiful, for he has no fur. Not having enough saliva, he has to wash h1mself with water. He miaows in a harsh voice and a great deal more than he need[s]. Sometimes in his sleep he purrs.

Open the door for me!

I do not know why he has made himself Master; perhaps he has eaten something sublime.

He keeps my rooms clean for me.

In his paws he carries a sharp black claw and he scratches with it on white sheets of paper. That is the only game he plays. He sleeps at night instead of by day, he cannot see in the dark, he has no pleasures. He never thinks of blood, never dreams of hunting or fighting; he never sings songs of love.

Often at night when I can hear mysterious and magic voices, when I can see that the darkness is all alive, he sits at the table with bent head and goes on and on, scratching with his black claw on the white papers. Don't imagine that I am at all interested in you. I am only listening to the soft whispering of your claw. Sometimes the whispering is silent, the poor dull head does not know how to go on playing, and then I am sorry for him and I miaow softly in sweet and sharp discord. Then my Man picks me up and buries his hot face in my fur. At those times he divines for an instant a glimpse of a higher life, and he sighs with happiness and purrs something which can almost be understood.

But don't think that I am at all interested in you. You have warmed me, and now I will go out again and listen to the dark voices.

Karel Čapek, Intimate Things, 1936.

14 June 2009

Scenes from the Billy Goat Trail

A friend and I hiked the Billy Goat Trail yesterday. We did the segment known as the "Section A", which goes above and along the Potomac River and offers some great views of the river.


The trail is conveniently marked with short patches of blue paint. Although at several spots it was difficult to see where the next patch was. At times like that, it is good to have more than one pair of eyes looking.


The National Park Service's description of the 1.7-mile trail as "extremely difficult and dangerous" is ridiculously inaccurate. A moderately fit person can hike the entire Section A without any difficulty. The greatest danger along the trail comes from the frequent patches of poison ivy that most hikers probably don't even recognize.

The most strenuous segment may be this steep climb, but even that isn't too difficult.


Here is a purple tadpole that was in one of the several rock pools we passed by. It was checking out a tiny fly that had fallen into the water.


12 June 2009

Cepaea nemoralis and its epiphragm

I have been keeping 2 live Cepaea nemoralis. I haven't bothered to look up how to best maintain them in captivity; I just put them in a plastic box with some wet paper towels and carrot skins and pieces of lettuce for food. There are several piles of fecal strings in the container, indicating that they are eating stuff, including the paper towel.

However, I often see them stuck on the underside of the lid as if they have a requirement to become dormant frequently. Last week I kept them in a dry container for a couple of days. When I examined them again yeaterday, the smaller one had sealed its aperture with an epiphragm.

You can see the pneumostome (breathing hole) of the of the snail on the right.

I returned them to their regular container and sprayed them with water. Earlier today the smaller snail had come out of its shell. Tonight they are both stuck on the underside of the lid again.

11 June 2009

Looking thru the shell of a snail


We are looking at a juvenile Mesodon thyroidus, a common land snail snail of northeast North America. Unlike the shells of old adults, its was still thin and translucent. So the flash shining from underneath revealed its organs.

The yellow arrow is pointing at the snail's lung, specifically, at the primary pulmonary vein. The long tube curving around the spire of the snail's shell, marked by the orange arrow, is the rectum at the end of the snail's digestive system. The dark matter filling it towards the back is feces on their way out. The white arrow is highlighting a red organ. Frankly, I am not sure of its identity. It could be the albumen gland or the ovotestis or a part of the digestive gland. When I get a chance, I will compare its position with those of the organs of some preserved Mesodon and come up with a more definite name for it.

Here is a previous post about another backlit snail.

10 June 2009

Idleness or laziness?

In a 3-page essay titled In Praise of Idleness, Karel Čapek described idleness as follows: (1) "idleness is not wasting time"; (2) "idleness is not the mother of wickedness"; (3) "idleness is not laziness".

Idleness is absolutely aimless; it seeks neither repose nor pleasure, absolutely nothing.
Čapek's essay was in his book Intimate Things (available at the Internet Archive), the English translation of which came out in 1936. About 5 years later in Sea of Cortez, John Steinbeck and Ed Ricketts praised laziness:
Only in laziness can one achieve a state of contemplation which is a balancing of values, a weighing of oneself against the world and the world against itself. A busy man cannot find time for such balancing. We do not think a lazy man can commit murders, nor great thefts, nor lead a mob. He would more likely to think about it and laugh.
Although their ideas were somewhat similar to those of Čapek, laziness espoused by Steinbeck and Ricketts was "a relaxation pregnant of activity, a sense of rest from which directed effort may arise". Čapek, on the other hand, even eliminated planning of future activities from his idleness:
To be idle is not even to rest. If you are resting you are doing something useful; you are preparing for further work. Idleness is without relation to any past or future work; it has no results and looks forward to nothing.
The period of laziness of Steinbeck and Ricketts was not only for thinking, but also for drinking beer. Čapek's idleness almost sounds like some sort of meditative state; the lifting up of a bottle of beer would have been too disruptive for him.

Take your pick.

09 June 2009

Bad book review: François Jacob's autobiography

François Jacob (born 1920) shared the 1965 Nobel Prize in Medicine for "discoveries concerning genetic control of enzyme and virus synthesis". In the 1970s he developed the idea of evolution being a tinkerer, because, as opposed to how an engineer usually works, adaptations almost always arise not from scratch, but from the modifications of existing molecules, organs or metabolic processes (for example, see Jacob, 1977).

I bought The Statue Within, Jacob's autobiography published in 1987 from the used bookstore hoping to learn a little bit more about a man who at some point in his life appears to have been an important scientist. Had I known boring would be a one-word summary of his life and ideas, or rather the way he presented them, I would have saved my $2 for a cup of coffee.

This is a tediously personal, rambling account of Jacob's life. The very 1st chapter begins depressingly with the memories of the sufferings and the death of a friend of Jacob's, continues with a discourse on suicide and them rambles on with fragments of events from his life. A perfect way to turn off your readers right from the beginning, don't you think so? And then there is excessive philosophizing throughout the book mostly in a disorganized manner. Here is an example: one long paragraph starts out with what appears to be an account of how Jacob tried to decide what kind of research he wanted to do in the beginning of his scientific career and ends with criticisms of Soviet genetics under Lysenko and French communists. Who cares?

Jacob appears to be an atheist preoccupied with death and dying and who may be subject to bouts of depression. I could only read randomly selected parts of the book and now wasting my time writing about it.

Jacob, F. 1977. Evolution and tinkering. Science 196:1161.

08 June 2009

Young robins motionless


These young robins—if I am not mistaken with my identification—were in the backyard late one afternoon last week*. Although they could fly, at least between the branches of the trees they were on, their chief defense against would-be predators seemed to be their ability to stand almost completely motionless for long periods. Certain predators, for example, cats may be more likely to detect a prey when the latter is moving. Thus, a prey that can sit still escapes detection as long as the predator is not too close. I remember one summer day several years ago when I put a chair out on the grass and sat down to read a book and then several minutes later noticed that there was a little baby rabbit among the grass blades next to my foot; it was watching me with wide open eyes while making not one move.

YoungRobin3 (2)

This defensive behavior, of course, provides opportunities for the photographer to get very close to its subject as long as he doesn't mind the increased risk of getting his camera or face splattered with fresh bird poop.


*Strictly speaking American Robin (Turdus migratorius).

07 June 2009

Scientific breakthrough of the century: crawling speed of slugs determined!

How fast does a slug crawl? From time immemorial, that profound question has occupied man's mind, puzzling and frustrating the primitive hunter-gatherers and the cerebral Nobel prize winners alike. Despite millennia of research and rumination, only recently has the humanity attained the necessary technological and intellectual stage to successfully tackle this seemingly insolvable conundrum. Snail's Tales is now proud to announce that a partial solution to the problem has indeed been obtained and will hereby be presented.

Without further ado, here is a slug of the species Arion subfuscus traveling vertically on a beech trunk. The horizontal lines mark the positions of the front of the slug's head at the indicated times.


The slug covered 106 mm in 4 minutes*, which corresponds to a speed of 26.5 mm/min. I carried out similar measurements with 2 other slugs of the same species. The fastest one was moving at 36 mm/min, or 2.2 m/hour, or 52 m/day, or about 19 km/year.

I noticed that while coming down the tree, the slugs had a peculiar mode of locomotion: it looked as if they were rappelling down using their slime. I don't know if anything has already been published on that, but I will return to the subject in the future.

I suspect that on a horizontal surface, especially on one that is not as smooth as a beech trunk, slugs' speeds will be less. The crawling speed of a slug may also depend on air temperature and humidity, whether or not the slug is also grazing on the tree surface while crawling, its species and size and the slope as well as the microscopic characteristics of the surface. There may be other factors that influence crawling speed.

We are continuing our research in this field of cutting edge malacology. Updates will be posted here.

*I ignored the slight curvature in the slug's path.

05 June 2009

A snail often on trees: Mesodon thyroidus


One of the seldom discussed characteristics of the common northeast American land snail Mesodon thyroidus is that it can often be seen on trees. Baker noted in his 1939 Fieldbook of Illinois Land Snails that "On humid days, the snails [Mesodon thyroidus] may often be seen crawling over the ground, over logs or even on standing trees several feet from the ground." So it is a known phenomenon*. But, as far as I know, there are no published studies specifically about it, looking at, for example, what the snails do on trees (they are probably eating something), how long they stay on them and how high they really go.

This snail was in the park near my house last weekend. After I photographed it, I removed it and looked into its aperture to ascertain that it was indeed Mesodon thyroidus, but not the superficially similar Neohelix albolabris**.


Yes, this one was indeed a Mesodon thyroidus. Notice how much its apex was worn; there was literally a hole thru it. Such damage is often inflicted by other snails trying to satisfy their calcium carbonate requirement in areas where there are no limestone rocks.

*Pilsbry, however, didn't mention the species' tree climbing habit in his Land Mollusca of North America.
**Mesodon thyroidus, usually the smaller of the two, often has a parietal tooth, which Neohelix albolabris often lacks.

04 June 2009

Somebody give these poor Christians a glass of wine

Still reading Thomas Asbridge's The First Crusade. In the previous post on this subject, the crusaders had laid siege to Antioch and were in the process of exchanging atrocities of all sorts with the defending Turks. Subsequently, the crusaders kicked the Turkish fighters out of the city and, in the true Crusader spirit, massacred the Moslems left behind.

Only a few days later, however, a massive Turkish army headed by Kerbogha arrived and surrounded the city; now it was the crusaders’ turn to be holed up inside the walls. Soon, starvation set in. Asbridge quotes a crusader’s account of the ordeal from Gesta Francorum:

The blasphemous enemies of God kept us so closely shut up in the city of Antioch that many of us died of hunger, for a small loaf cost a bezant, and I cannot tell you the price of wine. Our men ate the flesh of horses and asses; a hen cost fifteen shillings, an egg two, and a walnut a penny.
My first thought upon reading this was why a starving person would care about obtaining wine. Then it dawned on me that wine is a pretty good source of calories if nothing else. And calories in the form of simple sugars (glucose and fructose, especially the former) is what you need if your enemy is about to chop your head off unless you act first.

According to the USDA, one serving of Cabernet Sauvignon (~150 ml) provides 122 kcal of energy. The crusaders are unlikely to have washed down their horse steaks with Cabernet Sauvignon, but the caloric contents of different types of wines are more or less the same except for dessert wines, which have more carbohydrates and hence more calories. So we can safely assume the wine that was then available had about the same amount of calories. Nevertheless, it would still have made more sense to spend one’s last bezants for eggs and walnuts than for wine when water was presumably available for drinking.

But then again, there may have existed back then various ingrained opinions regarding the dangers of drinking too much water. Ogier Ghiselin de Busbecq, the Austrian Emperor Ferdinand’s ambassador to the Ottoman Empire, wrote in his fourth Turkish Letter (1562) about some Christian prisoners of war that had been brought to Istanbul. He was appalled by the Ottomans’ treatment of them and made arrangements to supplement their standard ration of bread and water with meat.
My house from early morning till evening was filled with a crowd of those who sought assistance for their different troubles. Some, who had been accustomed to sumptuous tables, could not digest their daily ration of dry black bread, and required the means of procuring some relish to eat with it. There were others whose stomachs could not endure perpetual water-drinking, and wanted a little wine to mix with it.
It is not clear how the prisoners, if they had indeed been imprisoned, could come to Busbecq’s house. But that’s besides the point; what is significant here for our purposes is Busbecq’s claim that their “stomachs could not endure perpetual water-drinking”.

There may have been some truth to the perceived dangers of drinking water in the Middle Ages. In densely populated cities, the available "potable" water was probably more often than not contaminated with human and animal waste and hence was a source of disease causing microorganisms. Wine with its ~14% alcohol content, on the other hand, would have offered a safer liquid to drink.

If I had not just finished my glass of Cabernet, I would offer a toast to the wisdom of the Middle Ages.

03 June 2009

First tick of the season

It has now become a routine for me to donate blood to at least one tick every year. Last year I returned from Illinois with a lone star tick attached to my leg. The year before, a tick and I enjoyed a Neil Young concert together.

I found this year's first tick on my arm last night 2 days after my last field trip, which was a successful search for the snail Cepaea nemoralis on Sunday. I got the tick either then or on Saturday when I was searching for slugs in the woods. Here it is on my arm still in the process of gorging itself on my hemoglobin.


My wife, who is an expert tick remover thanks to the frequent training opportunities I have provided for her over the years, quickly got it off. And here is a close-up of the beast.


It was ~1.5 mm long. I am assuming it is a nymph of a deer tick (Ixodes scapularis). I have posted a larger photo on BugGuide.net. Maybe I'll get a more definite identification from there.

Meanwhile, I still have an itchy, red swelling on my arm where the tick was.

02 June 2009

Huge spider with hairy legs


Last Saturday I saw this arachnid on a tree in the park near my house. It was about 2 m above the ground next to a large cavity, which was probably its hideout.

It's not possible to judge its size without a scale. Here is a picture of it with a ruler I was able to bring near it without making it run away. Its body was about 2.5 cm long.


It may have been the largest spider I have seen outside a zoo. Here is a close-up of the head.


I have posted another picture on BugGuide.Net. Hopefully, somebody will put a name on it.

01 June 2009

Next time in Istanbul stay at the Grand Hotel de Londres


And don't forget to spend some time in the ladies' hygienic baths.

From Handbook for Travellers in Asia Minor, Transcaucasia, Persia, Etc By Sir Charles William Wilson. 1895.