2 more data points (or is it datum points?)

Very little research has been published on the life cycle, ecology, behavior and the general biology of the native slugs (family Philomycidae) of northeastern North America. Megan Paustian and I started doing some work on the water loss and regain characteristics of one species, Megapallifera mutabilis, early in the spring of this year (see this post).

At about the same time, I decided to understand their annual generation cycle better, especially to figure out if adults survive the winter. It's a simple project, really. For 2 years, I will measure the body dimensions and/or weights of live slugs throughout the year. That's about it. The collective data will show how the members of the population change during the year. The important thing is to take as many measurements as possible on relatively warm days in December and also towards the end of March as soon as the weather starts to warm up. If there are large slugs in December and in March that will mean that the adults survive the winter.

The photograph shows 2 of the slugs getting weighed in the field about a week ago. They were adults and quite heavy, as far as this species goes.

Remains of a meal

In the bosom of a very distant relative

Among the numerous bone and mollusk shell fragments scattered throughout our yard is this old, thick clam shell. I have no recollection of where it came from and no idea what species it may have once represented.

The other day when I picked it up to move it elsewhere, I found these 3 slugs, Deroceras reticulatum, safely nestled on the underside of it.


The last common ancestor of gastropods and bivalves must have lived sometime in the Cambrian, more than 500 million years ago*. That makes them very distant relatives indeed. Nevertheless, I had no intention of interfering with their family union of sorts. I returned the clam shell with its inhabitants to its spot.


*Here is a brief intro to mollusk evolution.

Fall of the fallen beech

This is the horizontal beech tree that refuses to die. I visited it last weekend and saw that its leaves had turned yellow. Will it sprout green leaves next spring? We shall find out.

How science differs from pseudoscience - Part 2

The main, and perhaps the defining, characteristic of the domain of scientific knowledge (DSK) is that the units of information (or provisional truth) within the DSK form a network. This network is possible because the units of information do not contradict each other. And the outcome of this network is that the units of information support each other.

For example, our understanding of the essential processes of biology rely on and do not contradict the principles of physics and chemistry (no, the processes of life do not violate the 2nd law of thermodynamics). Our understanding of the essential processes of evolution, on the other hand, are supported by even additional scientific disciplines, for example, geology.

This is, of course, an idealistic description of science. There are always some minor contradictions within the DSK, because our understanding of nature is incomplete. One purpose of scientific research is then to reduce the number of the existing inconsistencies and, ultimately, to eliminate them all.

We can visualize the DSK as an N-dimensional information space without a definite center and with fuzzy or diffuse boundaries. The boundaries are not definite, because at the threshold of our existing knowledge there are always uncertainties.

In contrast, pseudoscience and religion lack comparable networks of compatible and mutually supportive truths. And their domains of knowledge have extremely diffuse boundaries. You want to be religious? Then you must pick one out of the many choices you have, because all of the existing religions are mutually exclusive. And besides, they all have severe internal contradictions.

There are 2 processes that advance science: (1) piecemeal accumulation of information either inside the DSK to fill in a gap (yes, there are also gaps) or at the edge to expand the boundary slightly; (2) revolutions or “transformations of paradigms” in Thomas S. Kuhn’s words.

Although Kuhn* may have believed that science advances primarily by revolutions, I don’t see why both processes cannot operate in tandem.

An observation done by a scientist represents the 1st process and the outcome is that some new bits of information are added to either the inside or the boundary of the DSK. For our purposes here, we are interested only in the boundary additions.

The crucial question is, How far from the boundary do new additions fall? The answer is, not too far; in fact, they fall quite close to it. They must fall quite close to the boundary. Otherwise, they will threaten the integrity of the DSK.

Part 1

To be continued.


*Disclaimer: I have so far read only a dozen or so pages of Thomas S. Kuhn’s often-cited 200-page essay The structure of scientific revolutions (2nd ed., 1970). My opinions of his opinions may change as I continue to read and understand his arguments.

Life under a brick

But no house can be smaller than a single brick.
Arthur C. Clarke, The road to Lilliput, 1973.

For a soil invertebrate, however, even a brick fragment could be an abode with plenty of room to share with others.


The other day, when I turned this piece of brick in my backyard over, I encountered a menagerie.

There were 2 species of isopods: the one on the left was probably an Armadillidium nasatum and the one in the middle probably a Porcellio scaber. The bug on the right is probably a true bug (hemipteran), but that's where my knowledge of them ends.


There were 2 species of snails: the small one on top is a Vertigo pygmaeum, while the larger one is a Cochlicopa lubrica. Both are common on and under the rocks in the yard.


Finally, the big woolly caterpillar is a woolly bear, the larva of the moth Pyrrharctica isabella. Those caterpillars are quite common around here, but I don't think I have ever seen the moth itself.

How science differs from pseudoscience - Part 1

A recent Science Weekly podcast of the Guardian included a lengthy interview with Chris French, a professor at the University of London who is studying "anomalistic psychology", defined as the psychology of paranormal beliefs and experiences. Regarding the commonly heard statement that one wouldn't believe in ghosts or angels (or whatever) unless one saw one with one's own eyes, professor French said the following (my transcription): "My attitude is even if you do think you see one with your own eyes then that doesn't really prove it."

Upon hearing this, I was initially puzzled. How can we discount our own observations? After all, the 3 fundamental sciences, physics, chemistry and biology, their theoretical branches notwithstanding, are essentially experimental and observational and experiments and observations in general, even when heavily aided by instruments, rely more on vision than any other senses. Probably because of that, blind scientists are rare, very rare; in fact, the only one I know is the remarkable Geerat Vermeij, a malagologist, incidentally, who has been completely blind since early childhood (more info).

Of course, scientists sometimes make erronous observations. Nevertheless, scientists' visual observations are normally not considered suspicious or unreliable. If I claimed that I saw a snail doing something and explained how it was doing it, my peers would believe me. But why should we accept the observations of a scientist, and be skeptical of those of a pseudoscientist? Double standards imply dishonesty, but scientific research is supposed to be an honest and a democratic process.

A scientist is more believable unless the reported observations are highly unusual. That is the keyword. Where a particular observation or claim fits within the already established knowledge seems to be the crucial difference between the scientific observations and the paranormal "observations".

Part 2

Caterpillar #2

This is the caterpillar I mentioned 2 days ago that I was going to write about. It was looping across a sidewalk when I first saw it. It was one of those geometrid caterpillars. I brought it in to film it like the previous one. But once inside, it refused to loop; instead, every time I tried to coax it into moving, it assumed various silly positions, pretending to be some inanimate numeral or a punctuation mark.

Here it is trying to make me think it was a quotation mark, I believe.


Eventually I gave up and released it.

A banquet in the yard for invertebrates

Early this evening, a partially eaten apple in the frontyard was the focal point of the activities of a multitude of invertebrate taxa. When I first arrived at the scene around 19:15, a whole bunch of ants and a slug that looked like a Deroceras reticulatum were on it.

When I went back out an hour later at 20:20, the Deroceras had left and its spot had been taken by a group of isopods of at least 2 species. A couple of slugs are also visible on the left. The brown one is an Arion subfuscus. Soon, the light of my lamp and my breath blowing over them sent most of the isopods scurrying into the darker corners.


Just then, as I was getting ready to get up and leave, a millipede made a brief appearance. But it didn't stop to take a bite; it looked like it was only checking things out.

A mysterious corpse on my desk

I sat down to write about a caterpillar I photographed yesterday. As I was putting down my beer bottle I noticed this thing that was on a piece of paper on the desk in front of me. Thinking that it was a piece of dust, I was about to blow it away when I noticed that it had wings and miscellaneous appendages. I don't know what it is and how it ended up in my basement. It is about 5 or 6 mm log; an accurate measurement is difficult, because the body is folded over itself.

OK, I have blown it away and it is now dust.

I will write about the caterpillar tomorrow. Maybe.

What does it mean when a snail's tentacles are vertical?

This is a juvenile snail, either a Mesodon thyroidus or a Neohelix albolabris. I brougt it home in the beginning of July and have been waiting since then for it to form its adult lip so that I can put a definite name on it, but its refusing to grow.

And why is it holding its tentacles vertically?

Who is eating the snail mail?

Why, snails, of course! The Times is reporting that in Great Britain unprecedented numbers of snails and slugs have been crawling into the mail boxes to dine on the mail. Not only that but they also leave everything covered with their slime!

The Times quotes a Post Office manager: “Slugs and snails are devouring the edges of letters and most of the stamps. They are everywhere at the moment because of the weather. All we can do is apologise to people and keep on putting the pellets in the box.”

Snails and slugs do eat paper. And despite the Royal Mail's claim that the mollusks are after the glue and the printing inks, it is actually the plain paper that they wouldn't mind eating. Paper is mostly cellulose and cellulose—from the plant matter they eat—is a major component of the normal diet of most snails and slugs.

That's is exactly why one should not put the locality information written on paper in the containers of live snails and slugs even if they are dormant. I try to follow my own advice, but there are occasional lapses. Here is a recent example. The corner of this locality tag was eaten away by the very slug hanging upside down underneath the lid within a few hours it took to bring it home.

Thanks to the reader xoggoth for bringing this news item to my attention.

Monocacy River gaging station

We came upon this peculiar structure during a field trip along the Monocacy River last summer.

If it hadn’t been for this nearby marker on the ground I wouldn’t have known that it was a U.S. Geological Survey gaging station.


There are no identifying numbers on the marker. After some searching at the USGS site, I found this station (USGS 01643000) that I believe is the same site. The station in the picture there looks like the station in my picture. However, when I plugged the coordinates they give in Google Earth, I ended up at a spot in the Monocacy River. I suspect the USGS coordinates were based on an old geodetic datum.

Nerodia sipedon on the road

I found this dead juvenile northern water snake (Nerodia sipedon) on a nearby road late one afternoon a few days ago. I poked it a few times and after I convinced myself that it was indeed dead, I wrapped it with a paper napkin and brought it home in my pocket (it was exactly 20.5 cm long—quite suitable to carry in one's shirt pocket).

The snake's body was supple without a noticeable odor and the eyes were still bright.



It had apparently died recently. But from what? There were no visible external injuries.

As its vernacular name implies, Nerodia sipedon lives in and near water. Interestingly, the spot where I found it was near where I had found a dead spotted salamander last November. How and why do these aquatic animals leaving their normal habitats and ending up on a road to die possibly from exposure?

The snake is now resting in alcohol. I will try to dissect it one day after I dissect the salamander first.

C&O Canal: then and now

I took this picture of the C&O Canal at Georgetown on 18 September. The Canal had been mostly without water at least since early September when I first started exploring the area (see this post).

Here is a picture I took from roughly the same spot on 9 October.


Where did all that water come from? We certainly haven't had enough rain to fill the Canal. The Park Service must have a way of bringing water from the Potomac River which is below and quite close to the Canal.

Temperature tribulations

Hasok Chang's 2004 book Inventing Temperature tells the long and intriguing history of thermometry, the science of the measurement of temperature. First, thermometers had to be invented, followed by methods to calibrate them. But to calibrate a thermometer at least one reproducible phenomenon that always took place at the same temperature was needed. But how would one know that something, say the boiling of water, always took place at the same temperature if one didn't have a calibrated thermometer? This circularity was behind most of the hurdles the pioneering thermometrists had to overcome. Finally, temperature scales, a multitude of them, were devised—almost one by each independent thermometer maker.

I learned quite a bit from this book. Among the more interesting episodes were a series of experiments by Marc-Auguste Pictet in the late 18th century that demonstrated quite puzzlingly that cold, like heat, could be reflected from a mirror (for details, read this 1985 paper by Evans & Popp) and the potter Josiah Wedgwood's (Charles Darwin's grandfather) almost contemporaneous invention of a pyrometer to measure very high temperatures—it used small pieces of clay, the amount of shrinkage of which at a given temperature were supposed to have been reproducible.

I wish Chang's prose were a bit more straight and readable and the contents of the book a bit more uniform. The first 4 of the 6 chapters have 2 parts each: a historical narrative followed by an analysis that dwells into philosophical issues that I thought were boring and not always relevant. I confess I skipped most of the analyses.

Chang ends his book with a chapter on complementary science, his research program that intends, by utilizing the historical and philosophical aspects of a particular scientific area, physics, in his case, to "generate scientific knowledge in places where science itself fails to do so." I find Chang's ideas provocative, but will try to criticize them in detail in another post.


Also posted in a slightly different form on Amazon.

Jimson weed at Georgetown University

Many years ago one spring, a peculiar plant I had never seen before started growing in our backyard. Subsequently, it bloomed and the flowers were quite showy, so I let it live. And then it developed large, green seed pods covered with spikes. Only some time after it died did I identify it as the jimson weed (Datura stramonium), a plant loaded with several hallucinogens that are especially toxic to livestock.

Although the jimson weed is said to be a common plant, especially in waste areas, I have not come across it very many times. So when I spotted one last Friday while walking past the small stadium on the campus of the Georgetown University in D.C., I decided to take a few pictures of it. Unfortunately, there was a chain link fence between us that prevented me from getting close to it.

Here is a slightly closer look at the seed pods.


If I am remembering it correctly the flowers of the jimson weed in my yard used to open early in the evening. I used to think that they were probably pollinated by some night-flying moths, but never saw moths or other potential pollinators at the flowers.

Anatomically incorrect salamander graffiti

I don't think there are salamanders with forked tongues.

Mysterious tracks in the C&O Canal - Part 2

In this post from early September, I had pictures of a series of parallel tracks in the mud of the C&O Canal in Georgetown, Washington, D.C. I also suspected that they were turtle tracks.

A couple of weeks ago I was able to get down into the canal and take closer shots of similar tracks on dry mud.

It looks like the hind foot steps very close to the print of the front foot, creating a series of double impressions. Also note the undulating groove in between the parallel foot prints, which, I suspect, was created by the tail.

Here is a close-up of one of the double foot prints. Are those claw marks that are visible in front of the lower print?


The next picture shows 2 sets of converging tracks. In this case only the bottom one had the tail impression.


They are probably turtle tracks, but I am still looking for definite proof.

Microorganisms in space? You can't be serious!

In the 03 October 2009 issue of the New Scientist, there is a review of a book called Comets and the Origin of Life by Wickramasinghe et al. The reviewer, someone named Marcus Chown, who is apparently judged to be qualified to write for the New Scientist, makes this claim:

...the case for planetary panspermia - the idea that micro-organisms transfer between planets - is now widely accepted...

This is a very bizarre remark. I would like to know which serious scientist has claimed that there are live microorganisms in transit between planets.

Putting such an ludicrous statement in print doesn't do anything good to the credibility of the New Scientist.

Inchworm goes a-loopin'

This larva of a geometrid moth was in my backyard last Sunday. Prior to watching this video (and 2 others I took of it), I had never paid close attention to the mechanics of their looping. One characteristic that struck me right away was that, unlike the front end, the back end is never lifted off the surface; it seems that it is simply dragged forward without losing contact with the substrate. The next time I see one of these I will try to get close-up shots.

Backyard banana feast with slugs and others

Last Friday night around 11:30 in my backyard a discarded banana peel that had ended up in the flower bed instead of the compost pile was the focus of attention of several species of local invertebrates. Among them were slugs, including these that were probably Arion subfuscus. Also notice the small spider near the top lefthand corner.

Many isopods had also joined the feast. In this picture the one on the left may be an Armadillidium nasatum, while the one on the right may be a Philoscia muscorum.


At one point I noticed a black beetle within the folds of the banana peel. I had just gotten the camera ready, when it surfaced, briefly "sampled" one of the slugs and then disappeared.

Snails (and a deer skull) from a field trip

Taking advantage of the sunny and warm weather, I spent several hours in the field this afternoon.

Among the several snail species I encountered was this Anguispira with a prominent keel around the periphery of its body whorl. This is the typical morph of the species along the Potomac and Monocacy Rivers in Maryland. I have been calling them Anguispira alternata, although I am not sure if they are not a different species.

Note the reddish foot of the snail, which is typical of Anguispira alternata.

Here is a deer skull I saw.


One of the most common land snail species around here is Ventridens ligera. They can be found not only in in forests but also in open fields and even along railroads. All of these shells came from one location in the woods. if I had searched longer, I probably would have found more.


Finally, Cepaea nemoralis again! Note that each of these live snails, found next to each other, represented a different variety: the one in the middle was bandless, the one on the left had a single band and the one on the right had 5 bands.

Don’t store your specimens in your mouth!

In his autobiography Charles Darwin told the story of how he once during a collection trip had picked up a beetle in each hand and and put the 3rd one in his mouth and how the latter had responded by releasing an “intensely acrid fluid” burning his mouth.

Here is a similar story by Henry Pilsbry from an 1892 paper of his. In this case, the unidentified “rare specimen” was undoubtedly a snail.

It may be remarked that the custom of holding specimens between the lips is not so rare with field naturalists as fastidious persons might suppose. I confess to having once swallowed a small and very rare specimen while holding it for a moment. The creature was, alas! not my own property, and its outraged owner has not yet forgiven me.

I don’t think I’ve ever put a specimen, snail or otherwise, in my mouth for safekeeping, but I do remember witnessing a friend cleaning the mud off of tiny shells by putting them on his tongue and then rubbing them against the top of his mouth.

A message for the immorals among us

In the 26 September issue of the New Scientist there is an essay by Paul and Anne Ehrlich. They write:

Somehow, cultural attitudes toward large families everywhere need to be changed. It should be considered immoral to have excessive numbers of children - an attitude that already exists in most industrialised nations with low birth rates. Nothing is more clearly a governmental responsibility than keeping a nation's population size sustainable by benevolent measures.

I completely agree with them in that it is indeed necessary to change the general conviction prevalent in many countries that having many children is a virtue. In the U.S. where the abnormally high religiosity of the general population is probably at least partially responsible for the tendency to have large families, which is the norm even among the more educated segments of the society and which creates an exception among industrialized nations.

However, I don't quite understand what a government can accomplish in this respect especially if the government itself is openly or covertly on the side of the religion.