making an intensive study of the insect eye and the physiology of the
insect sense of smell. Previous research has shown that worker bees
have a special scent gland under voluntary control. Only when a good
source of nectar is found is the fragrance, evidently quite powerful
and attractive to other bees, released. Then it permeates the immediate
neighborhood. It is the bee language equivalent for the word “Here.”
When a cruising worker gets a whiff of this odor it knows there is a
plentiful supply of nectar close at hand and starts a search for it.
Bees cannot distinguish red from black, Dr. von Frisch has found.
This probably is the reason so few red-blossoming plants depend on
these insects for distributing their pollen. Nearly all red-blossoming
species depend on birds and butterflies, both of which are acutely
sensitive to red. One notable exception, however, is the European poppy
whose brilliant red blossoms carpet the landscape in late Spring. The
German experimenter has found that these blossoms are not “red” to the
bee. They possess a color which cannot be described because it cannot
be experienced by the human eye. The poppy blossoms reflect a great
deal of the ultraviolet light in sunshine and to this the bee eye is
extremely sensitive. The color must be quite different from any of the
shades at the blue end of the spectrum which are visible to man. To the
bee it is probably somewhat like violet.
Even the more or less degenerate human nose can be trained to
discriminate some of the bee odors that apparently have so much meaning
in the life of the hive. After practising for a few months Dr. N. E.
McIndoo of the U. S. Department of Agriculture was able to recognize
the three castes—queens, drones and workers—merely by smelling them.
With more practice he was able to make even finer discriminations, as
he reports:
“The younger the workers the less pronounced is the odor emitted. To
the human nose the odor from nurse bees and wax generators is much less
pronounced than is that from old workers. Workers just emerged from the
cells have a faint, sweetish odor, but lack the characteristic bee odor
and workers removed from the cells just before they begin cutting their
way out omit a still fainter sweetish odor.
“Old queens have a strong sweetish odor, while that of queens just
emerged from cells is much pronounced as is the bee odor of the
workers. The majority of old drones have a faint odor while every young
drone has a stronger one. It is slightly different from that of young
workers and is less sweetish.
“All the offspring of the same queen seem to inherit a peculiar odor
from her, which becomes the family odor. Apparently each worker emits
an individual odor which is different from that of any other worker.
“Of all odors, that of the hive is most important. It seems to be
the most fundamental factor upon which the social life of the colony
depends, and upon which the social habit perhaps was acquired.”
Taste discrimination is roughly parallel to that of humans. The bee
certainly can distinguish the primary tastes, sweet, salty, sour
and bitter. It naturally is keenly sensitive to different degrees
of sweetness, yet some sugars which are extremely sweet to man are
tasteless to the insects. The same is true of such sweeteners as
saccharin. The bee’s sense of smell also runs parallel to that of man,
both in the ability to discriminate fine difference in odors and in the
thresholds of sensitivity. This appears to be a very important factor
in the location of nectar-bearing flowers. However, the bee appears
unable to detect an odor from any great distance. It is probably due
to the sense of smell that scout bees are able to locate good feeding
grounds. After marking them with their own peculiar secreted odor they
return immediately to the hive to tell the others about them. The dance
of a returned scout varies in intensity according to the richness of
the find and the workers who witness it become correspondingly excited.
If the scout executes only a feeble dance there is only a small exodus
from the hive.
_Poisonous Platters of the Sea_
One of the most dreaded of all sea creatures is the venomous sting
ray of which there are several hundred species distributed over the
world, mostly in tropical waters. On the upper side of the tail is a
saw-toothed bone dagger from two to fifteen inches long which can be
driven through a man’s leg. The teeth extrude a venom quite similar to
that of the rattlesnake.
Largest is the giant sting ray of Australian waters. A full-grown
specimen weighs about 800 pounds. The fearsome and gruesome bat sting
ray of the California coast weighs up to 200 pounds and is quite
abundant.
All the rays are bottom dwelling animals, leading sedentary lives on
flat, sandy ground. All are carnivorous, devouring smaller fish and
mollusks. Fortunately they are not very aggressive and will flee from
man if given warning. Still, life guard stations along the California
beaches reported nearly 400 injuries from the creatures in the summer
of 1952.
_Our Un-American Food_
A half dozen vanished civilizations make their contributions to the
American Thanksgiving dinner: onions from ancient Egypt, peas from
Ethiopia, parsnips and turnips from ancient China.
Aztec, Maya, the skin-wrapped Cro-Magnon all did their part in the
darkness of pre-history to make possible the plates which are loaded so
lavishly. They did better than they knew. Very few new vegetables have
been introduced in historic times. In many cases little improvement has
been made on the products of the ancients.
The story of potatoes alone contains enough romance and adventure
for a good-sized novel. Its origin is unknown but its wanderings from
America to Europe and back to America again constitute a fascinating
story.
Cultivated lettuce never has been found wild. It is believed to have
been derived from India or Central Asia. It is one of the oldest
known vegetables. Herodotus, Hippocrates and Aristotle mention it in
references to Greek gardens. Chaucer notes its cultivation in England
in 1340. Sixteen varieties are listed as being grown in American
gardens as early as 1806.
Celery is a biennial plant native to the marshlands of southern Europe,
North Africa and southwestern Asia. It long was considered poisonous
and was not used as food until modern times.
The Israelites complained to Moses in the Wilderness because they
couldn’t have onions to which they had become accustomed during the
captivity in Egypt. The cultivated onion probably originated in
Afghanistan.
Pumpkins and squashes were grown in America long before white men
came on the scene. Evidence of both have been found among ruins of
settlements of the Basket Makers, about the earliest agricultural
people on this continent. They probably came from Mexico. The Hubbard
squash came to light in Marblehead, Mass., in 1855. It had been growing
there for more than 50 years.
Peas are the oldest known vegetables. They are believed to have
originated in Ethiopia but to have spread over Europe and Asia long
before the dawn of history. They were eaten—perhaps even cultivated
after a fashion—by men of Europe’s Stone Age. Columbus planted some
in the West Indies in 1493. They spread rapidly among the Indians and
became one of the chief crops of the Iroquois.
The species from which cabbage is derived grows wild in North Africa
and along the European shore of the Mediterranean. It has been
cultivated for 4,000 years. Greeks and Romans grew it in their gardens.
Most of the American varieties, however, originated in North Europe.
The turnip is a native of central and western China. Seed probably was
brought to America by some of the earliest European settlers.
The radish is a native of China and India. It was cultivated by both
the Greeks and the Egyptians. The parsnip is another Asiatic root crop.
It first was planted in Virginia in 1690. Only recently has it gotten
away from the home garden to become a commercial crop.
Popcorn is peculiarly American. In early Spanish writings reference is
made to a ritual of the Aztecs in which “one hour before dawn there
sallied forth all these maidens crowned with garlands of maize, toasted
and popped, the grains of which were like orange blossoms—and on their
necks thick festoons of the same which passed under the left arm.”
_Worms That Commit Mass Suicide_
An entire generation of worms commits suicide every year. Every
individual casts off its own head.
These worms are a Himalayan variety of naids, fresh water animals
vaguely related to earthworms. They are reddish-brown and seldom more
than an inch long. The majority of the worms live with their heads
buried in the mud, tail ends waving freely in the air. Upon any alarm
their bodies contract leaving no signs of life.
Early in the Spring these worms literally lose these heads and die.
Compared with those of most worms, their regenerative powers are quite
feeble. It is believed that the decapitation is due to the fact that
egg-laying is accompanied by such violent contractions of the body that
the front segments are disconnected.
Every few years there is a report from somewhere in the United States
or Europe of enormous numbers of dead earthworms covering the ground.
A correspondent of the British scientific journal, Nature, reported in
1921: “About the middle of March I saw millions of dead worms morning
after morning on pavements, roads and paths. They were great and small,
young and old, of every known species and genus. They lay prone and
even when they were able to reach a grass plot alive they lacked the
power to burrow.” The phenomenon is unexplained. Examination of the
dead worms shows no unusual parasite or evidence of disease.
_Fish That Survive Freezing_
There is a realm of “supercooled life.” Its denizens are deep water
fish that live long and happily in temperatures below the freezing
point of their blood. But whenever one of them comes in contact with
even a single crystal of ice it freezes almost instantly. This strange
phenomenon of marine life has been observed by biologists of the Woods
Hole Oceanographic Institute.
These particular fish live at the bottom of Hebron fjord in northern
Labrador. The temperature there is about 1.7 below zero centigrade.
Some have been caught, brought to the surface, and then plunged into a
bath of sea water cooled to exactly the same temperature. They survived
for several hours. When, however, one of them came in contact with
an ice crystal, it froze stiff in a few seconds. The explanation, it
appears, is that these fish normally live below the depth at which it
is possible for ice crystals to form in water.
Very careful experiments have shown that water can be carried far
below its normal freezing point if it is kept entirely motionless
and is absolutely free from minute particles of any sort which
are necessary for the formation of ice crystals. This is about
the condition that exists at the fjord bottom. Eventually, if the
temperature is taken lower and lower, such water will solidify, but
into a form far different from ice. It is noncrystalline and can best
be compared with glass. But even if this happened in the Hebron fjord
it would not necessarily bother the fish. Their blood presumably would
turn to glass. There would be no breaking of body cells such as results
from the swelling of ice crystals. After an indefinite period the
animals might be brought out of the solid state, if the thawing could
be accomplished quickly enough, none the worse for their experience.
This has been accomplished with very minute organisms, but any
techniques which might be used with higher plants or animals have not
yet been discovered.
The extent of life in the supercooled world is unknown. It hardly can
be confined to fish. All sorts of mollusks, echinoderms and worms also
are bottom dwellers in Arctic and Antarctic waters. It’s not cold, but
ice, that kills.
_Plants That Kill_
The lethal dose Socrates was condemned to swallow by the
stuffed-shirtism of ancient Athens was d-propyl-piperidine. This is the
deadly alkaloid in the spotted hemlock, a common European weed which
now grows extensively over most of the eastern United States. A closely
related European species is the cowbane which cows instinctively will
not nibble.
The devastating illness which fell upon 10,000 Greeks of the
Anabasis, Xenophon would have been interested to know, was caused
by andromedotoxin. This is a resinous substance common to plants of
the heath family the world over. It is the poisonous constituent of
rhododendron, mountain laurel and some kinds of azalgias. Honey from
the blossoms of plants containing it is extremely poisonous.
When pioneers first pushed their way over the Appalachians their
settlements were ravaged by epidemics of a fatal disease—milk sickness.
Farms and villages were abandoned as terror-stricken settlers fled
from the scourge. It was due to tremetol, a complex chemical which has
been found in several plants—chiefly white snakeroot which causes the
disease east of the Mississippi. When cows eat the snakeroot the poison
passes into the milk.
By far the most virulent plant growing in the United States is very
little known although it has caused many fatalities. This is the
water hemlock or cicula—very different from the spotted hemlock whose
extract was forced upon Socrates. It grows in low, swampy places nearly
everywhere. When the ground is soft in the spring its roots can be
pulled easily from the soil and have a pleasant odor that attracts
children. It causes heavy losses of livestock.
Next in virulence of all American plants is the whorled milkweed which
contains a closely allied resinous material not yet satisfactorily
analyzed. It has caused the death of countless cattle.
_Caterpillars That Pretend to be Snakes_
There are worm-snakes, snake-worms, and wormlike animals that
instinctively imitate snakes. This is especially true of certain South
American caterpillars—defenseless creatures whose only security is in
mimicry.
A large, green tree-living caterpillar in British Guiana ordinarily
remains motionless and looks like part of a vine stem. But when the
branch is shaken it rears the front part of its body and stretches
horizontally. At the same time it gives a twist expanding its front
segment into a bulbous enlargement with a big menacing black eyespot
surrounded by a yellow ring. This it remains for a few minutes, looking
very much like a poisonous tree snake that lives among green leaves.
Serpent caterpillars abound in Brazil. The best example is Leucorhampha
triptolemus, a creature that hangs vertically from stems of plants.
When disturbed it twists and shows a front extremely resembling the
head and back of a snake. The curve of the caterpillar is just like
that of a serpent. It keeps up a swaying, side-to-side movement for
several seconds. The whole effect is to change what seems an innocent
plant stem suddenly into an open-mouthed snake with red jaws and
ferocious eyes.
_All Plants Are Luminous_
All green foliage gives off an invisible deep red—almost black—light.
This phenomenon is one of the most fundamental processes of life. It is
associated closely with the photosynthesis upon which depends all life
on earth. This important discovery was made recently by biologists at
the Oak Ridge laboratory of the Atomic Energy Commission while studying
changes in a chemical known as adenosine triphosphate in plants engaged
in photosynthesis, the formation of starches and sugars out of hydrogen
from the soil and carbon from the atmosphere in the presence of light.
Newly acquired knowledge about the process is paving the way to
improved agricultural methods.
The biologists used extracts from the bodies of fireflies which give
off a bright light when this chemical—an important source of energy
in muscle—is present. Then they found that chloroplasts, the parts of
plants most closely associated with the photosynthetic process, also
would give off light when mixed with firefly juice and illuminated.
They then made the unexpected discovery that living extracts of green
plants give off a light of their own without any mixing.
The light given off by the chloroplasts now is believed to be the exact
opposite of the first chemical step in photosynthesis. Light absorbed
by the chloroplasts forms unstable chemical bonds within the plant.
A small fraction of these chemically induced compounds recombine.
The energy liberated by this process is trapped by the chlorophyll
molecule, which in turn gives off the mysterious light.
It has been established that leaves, if frozen while exposed to
illumination, retain their light-producing ability for several months.
It also has been found that certain extracts prepared from leaves
undergoing exposure to light contain substances which give off a bright
light when certain chemicals are added to them.
_Worms That Live in the Snow_
There are jet black worms that live in red snow. They come out of their
snow burrows only during the late summer evening, crawl sluggishly on
the surface, and disappear at sunrise the next morning. They have been
observed swimming in shallow pools that form on the surface of the
great Malaspina glacier which flows down the slope of Mount St. Elias
in Alaska.
Presumably during the long sub-Arctic winter these worms burrow deep
in the snow and remain in a torpid state. They subsist chiefly on the
microscopic red algae which give the glacial snow fields a reddish
tinge. The black worms themselves are innumerable. They have been
photographed covering a trail a quarter-mile long at an elevation of
5200 feet in Oregon. They are enchytraeids, relatives of earthworms.
The common white variety now is raised commercially in vast numbers,
on diets of oat meal and sour milk, as food for fancy varieties of
aquarium fish. Both worms and insects that normally live in snow fields
are black.
An investigator of the Woods Hole Marine Biological Laboratory once
found a multitude of white enchytraeids in cakes of ice cut from a
Massachusetts pond the previous winter. They were active when the ice
thawed but all died in a few days. The same investigator kept thirty
specimens of another species in a tumbler of water placed on a ledge
outside his laboratory window. On a cold night the water froze solid
with the worms in a tangled mass in the center of the ice cake. All
but three or four were alive and appeared normal when the ice was
thawed.
About 75 years ago housewives of Salina, Kansas, complained that
the ice delivered from door to door was “wormy.” Cakes were found
honeycombed with tiny white worms, probably enchytraeids. They swam
about actively when the ice thawed and infested food stored in
refrigerators. All died when the temperature reached about 60 F.
Whether any worm—except possibly the most minute—can survive complete
freezing is doubtful. They live in little holes that form naturally
when water freezes and that are kept open by heat generated by the
bodies of the creatures themselves.
_The Strange Ways of Snails_
Among earth’s deadliest creatures are cone snails which inject into
their victims a poison as virulent as that of the rattlesnakes. These
snail-like animals have a poison-secreting gland in the head and the
venom is injected through the skin of the victim by tiny, needle-sharp,
harpoon-shaped teeth. It is deadly not only to many kinds of sea
animals but also to man. The poison, acting on the nervous system, may
in some cases kill in several hours.
Fortunately cone-shells are timid, retiring, slow-moving creatures.
They are among the loveliest of all sea shells. Most valuable is the
“glory-of-the-seas” cone which is worth several hundred dollars. Of
the twenty known specimens in the world, only three are in American
collections. Of the 300 or more known varieties only five or six from
the Indo-Pacific area are definitely known to be venomous.
The “emperor’s top shell” is among the earth’s most exquisite and,
until recently the rarest of sea shells. This shell, about five
inches in diameter, belongs to a sea snail of a genus fairly abundant
during the Mesozioc geological period about 300,000,000 years ago and
supposedly extinct until about eight years ago when one was found
alive in a Japanese lobster trap. Thereafter the snail was seen very
rarely until the present Emperor of Japan ordered that all specimens
be preserved for his private collection. Fortunately his interest
encouraged Japanese fishermen to keep a special look-out for the
creatures and since then they have been found quite frequently. They
apparently are distributed around the world in semi-tropical waters.
Two species have been located in the West Indies and a new one recently
has been reported in South Africa. The shells are rich golden-orange in
color, highlighted with reds and salmons.
In the Smithsonian collections are specimens of the “original shell
collector”—the snail that collects shells. This sea snail, widely
distributed in tropical waters, has the habit of gluing to its own
shell fragments of the shells of other animals, bits of coral, and
almost every kind of debris it can pick up. The purpose is not known,
but it may be for protective camouflage. Seen in shallow water, the
creature looks like a little pile of broken shells on the sea bottom.
There is a “worm snail” that builds great limestone causeways and
bridges. This is the shelled sea-snail of the Mediterranean—Termetus
(wormlike). When the creature is young its shell is a regular spiral
which the owner, free to move about, carries on its back and into
which it can retreat when alarmed. As the snail ages the shell becomes
twisted and contorted, like a tube, and is attached to an offshore
rock. The animal crawls inside and soon dies. There are inestimably
great numbers of these gastropods. They fix their shell tombs close
together. These coil around each other to form solid masses of rock.
Quatrefages, describes them in these words: “In Sicily where calcarous
rocks projected into the sea I found they were surrounded by a kind of
causeway which, without varying much in width, yet followed all the
sinuosities of the shore almost exactly on a level with the surface of
the water, filling up narrow chasms in some places and forming solid
archways in others. Thus it afforded a smooth and easy path to one
who did not object to having his legs washed by the waves. One might
suppose the white and compact cement had been consolidated by man.”
The love life of some snails is confusing to Freudians. Each animal
is provided with a quiver full of arrows, located in the right side
of the neck. These darts can be discharged with considerable force.
They are straight or curved shafts of carbonate of lime which taper to
exceedingly fine points. During the breeding season the little mollusks
meet in pairs. A couple will station themselves about an inch apart
and start shooting at each other. Several darts are exchanged and each
finds its mark. After this love duel the two embrace and, since each is
both male and female, both lay eggs. The darts presumably were first
developed as defense weapons and, outmoded for service of Mars millions
of generations ago, now have been turned to the service of Eros.
Showers of snails have been reported intermittently. One of the most
notable took place back in 1892 at the German town of Padeborn. Late in
August a great yellow cloud was seen over the town. In a few minutes
it burst into a torrential rain. Afterwards the pavements were covered
with water snails, all with shells broken after their long fall from
the sky.
Some snails can bore holes in solid rock. One, found chiefly on the
French channel coast near Boulogne, has bored holes six inches deep and
an inch in diameter with a cup-shaped cavity at the bottom. The cavity
is used for the animal’s hibernation.
A few snails are natural barometers. They reputedly are extremely
sensitive to changes in humidity. One, generally grey, turns yellow
just before a rain and blue afterwards.