SPIDERS are among the most ubiquitous of living organisms. They live wherever man does, including the heart of big cities. Accordingly they are a good subject for the city person who seeks to study a living member of his natural environment. One such student is Martin Romane, who attends high school in New York City. Last year he won a number of awards in the Annual Science Talent Search with his experiments on spiders of the kind that make webs. Romane writes about his investigations as follows:

"I have always enjoyed wild animals, even though New York does not rank high as a natural preserve. Staten Island, where I live, has squirrels, rabbits, muskrats, raccoons and even an occasional deer. The larger animals are not plentiful, nor are they convenient to capture for study at home. For this reason I did not take an active interest in animal behavior until three years ago, when I happened to see a spider spinning its web in our backyard. It was a drab gray and about a quarter of an inch long. What impressed me was the speed of the operation. The spider paid out silk at a dead run. It would attach a strand to a blade of grass, race across the ground to a bush and climb to a branch, paying out the silk en route. Without appearing to stop, it would then pull in the slack, anchor the end and sprint down the taut line to begin another attachment. The web was rather a slapdash affair. Strands ran in every direction, were of various lengths and appeared to be anchored at random. It occurred to me that the spider might not be following a specific plan and in its haste would not detect a missing strand if I were to break one. To test this idea I heated a sewing needle with a match and with it cut out one short strand near a comer of the web. The spider soon rushed to the spot, inspected the damage and promptly replaced the missing silk. That did it! A dozen other questions came to my mind. Would the spider spin a second web exactly like the first? Would all spiders of the species make identical webs? What would happen if one member of the species were transferred to the web of another member, and so on?

"Our school library has a number of excellent books about spiders. From them I learned that we are rarely more than a few feet from a spider, even when we travel by auto. Spider webs can be found under the seats and in the crannies of baggage compartments in aircraft. In even the cleanest of houses spiders live behind bookshelves, on the backs of framed pictures and in overstuffed furniture. Outdoors, particularly in grassy areas of the city, I have counted more than 120 spiders per square yard, a population density of more than a million individuals per acre. The variety of spiders is almost as impressive as their number. I have found more than 100 kinds on Staten Island, perhaps a tenth of the local species. According to the books, about 2,500 species are found in the U.S. Each species is characterized by its own pattern of behavior. Some trap their prey in webs. Others make no webs; they run down their prey as wolves do. Others crouch in a selected spot until the prey wanders within range and then jump to make the kill. Some species live only a year or two. Others, such as the tarantula, can survive for 25 years.

"Summer is the best time to collect specimens. They are in the open and are actively reproducing. The majority of the kinds that trap their prey build webs in shrubs, low bushes, grasses, under stones and on or in man-made structures. Collected specimens can be preserved in alcohol or maintained in captivity. I am interested primarily in the behavior of the web spinners and therefore maintain live specimens in cages. Confinement undoubtedly alters the behavior of the specimens in some respects. For example, some reference texts state that the female spider always kills and eats the male immediately after mating. This is disputed by Roman Vishniac, the well-known microscopist and naturalist. He believes that cannibalism is the rule when mating spider are caged but not when they are free in natural surroundings that allow the male to escape. Caging does not appear to influence other aspects of the spider's behavior. A live collection has the great advantage of enabling the observer to examine the insects at any hour of the day and in winter, when specimens are hard to find outdoors.

"A cage can be almost any box or jar of ample size. In the case of the web spinners the container should be large enough to accommodate webs of the size found in nature. This limits the collector somewhat. For example, I have not attempted to collect Aranea, the species that spins orb webs (webs that have a bull's-eye pattern) up to eight feet in diameter. My cages are cubic boxes made of quarter-inch plywood. I cut an air hole about half an inch in diameter in one side and cover it on the outside with a screen cut from a discarded nylon stocking. Usually I fasten the screen in place with pressure-sensitive tape. The transparent lid of the box can be a sheet of plastic kitchen wrap held in place with a rubber band. As an alternative I have used window glass for lids. Metal slides that accept sheet glass can be attached to the rim of the box. The slides are available from hard ware dealers. Glass is convenient for covering cages that must be opened frequently for making experiments. The interior of the cages is sprayed with flat black paint to provide a background o maximum contrast for viewing the webs. The cages should not be used for a week after they have been painted: the evaporating fumes might poison the spiders.

"When I am collecting, I take along several glass jars with a wide mouth and a screw cap, a hand lens for identification, a notebook and a small net. The net is used mostly for capturing spiders of the wolf type and the jumpers. I simply scoop material from the ground and sift or otherwise separate the contents until the specimens become visible. The general location of the web spinners is easy to spot. Look for the webs. Not all web spinners are found on the webs, however. Some attach a strand of silk that functions as a telegraph line between the center of the web and a remote location where they wait for prey. They keep their forelegs on the signal line and sense disturbances of the web by feel. When an insect launches a signal by agitating the web, the spider rushes from its lair by means of the line.

"Spiders feed exclusively on live prey. With few exceptions they will not eat anything they do not kill themselves. They must also have water. Those that make webs will stop spinning unless they are fed about once a week. According to the scientific literature, spiders have survived without food for as long as 18 months, but without water they die within 90 days. Feeding is simple. Just drop three or four insects into the cage once a week. The weight of each insect should approximate the weight of the spider. Water also need be supplied only once a week. With a pair of forceps grasp a tuft of cotton some four times larger than the body of the spider, saturate it with water and put it in the cage. The spider will suck water from the cotton just as it draws body fluids from the insects on which it feeds. Do not place bulk water in the cage, not even a single drop. A small spider may be drawn into the liquid by surface tension and drown.

"A diet of houseflies will keep the spiders active through the winter months. The flies are easy to raise. With a net or trap catch two dozen or so in the fall and transfer them to a wide-mouthed container with a capacity of about a gallon. That number should ensure that the captives include at least one male and one female. Close the container with plastic fly screening. The flies can be fed a mixture of dried milk and sugar in equal proportions, to which sufficient water is added to make a stiff paste. Place a dab of the mixture in the cage and with a medicine dropper add sufficient water from time to time to keep the food moist. Water the flies, like the spiders, with moist cotton. Within a few days the flies will be ready to lay eggs. Make an incubator of a second container, preferably of clear plastic. The incubator can be smaller, perhaps a pint jar. It must be connected to the cage so that the Hies can find their way between the containers. I simply cut a hole in the bottom of the cage and set it on the open top of the incubator.

"A good medium on which houseflies will lay eggs can be made by soaking a tablespoon of dry dog food in warm water for a few minutes, draining off the excess water and mixing into the dog food about a quarter of a cake of dry yeast. Transfer the medium loosely to the bottom of the incubator and place the apparatus in the warmest part of the house. The yeast grows on the dog food and the fly larvae will feed on the yeast. Moisten the medium from time to time. Within a day or so the flies should have laid eggs in the medium. The maggots will appear a few days later and young flies shortly thereafter. Adults can be harvested by folding back a corner of the plastic screening and inverting a wide-mouthed bottle over the opening. Flies that climb up into the bottle can be trapped for transfer to the spiders by slipping a small sheet of cardboard between the mouth of the bottle and the screening. Experimenters who are mechanically inclined can undoubtedly improvise a more elegant apparatus, but this simple arrangement works.

"The notebook is an important accessory. When I am collecting I keep a record of the location and date on which each specimen is taken. The information comes in handy when additional specimens of the same species are desired. By using a hand lens and referring to a handbook I try to identify and record the species of each specimen as I collect it. A few of the handbooks I have used are listed in the bibliography of this issue of Scientific American [below]. Thereafter I keep a running account of the behavior of all specimens: the nature of the web, the frequency with which webs are spun and the length of time the spider takes to spin its web. This information is useful during subsequent experiments. By knowing how a spider should behave under given conditions it is easy to spot departures from that behavior when the conditions are modified.

"I have been particularly interested in recording the pattern of webs. Some webs are so intricate that they are difficult to draw. Webs can be photographed, however, even though some of the filaments are almost invisibly thin, by dusting the silk with a white powder that makes every strand appear in sharp contrast to the black background of the cages. To dust a web, place a few drops of household ammonia in a small glass container and an equal amount of hydrochloric acid in a second container. I use whiskey glasses for containers. Remove the spider and set the containers side by side under the web. The rising vapors react chemically to form a white cloud composed of ammonium chloride in the form of microscopic crystals. Many crystals collect on the silk. Within less than 30 minutes the web will be coated with a white layer that can be photographed nicely when it is lighted from the side. The crystals do not seem to annoy the spider after it is returned to the cage, nor do they damage the web. The acid is corrosive and should be handled accordingly. The crystals are only mildly toxic but should not be inhaled.

"Specimens can be photographed by conventional techniques and can also be preserved in alcohol. To preserve a specimen drop the spider into a jar and add undiluted rubbing alcohol. If the insect is larger than a grain of rice, change the alcohol after a week to compensate for the dilution of the alcohol by the spider's body fluids. The cap of the jar should have a rubber ring to prevent evaporation.

"The number of experiments that can be made with spiders appears to be limited only by the number of questions that come to mind as you observe their ways. As I have mentioned, the first experiment I conducted involved destroying one strand in a web to see if the spider would replace it.

"Will a spider accept the web made by another spider of the same species? Experiments that I conducted with the two species Aranea tepidariorum and Steatoda tnangulosa suggest that at least some spiders will. A pair of spiders of each species, one spider per cage, were allowed to spin their webs. The individuals were then switched: spider A of one species was transferred to the web of spider B of the same species, and vice versa. In each experiment both spiders spent some time exploring the strange webs, after which each made certain additions. When the additions were finished, each spider appeared to be content and settled down to await the arrival of its prey. The webs of these species appear to be haphazard affairs with strands of various lengths running in every direction. Yet the experiments suggest that the web patterns cannot be fully random. Spiders of these species appear to recognize instinctively that the similar web of another individual departs from its own ideal pattern. They modify the structure in some trivial way. Other experiments suggest that not all species are so fussy.

"Comparable experiments can be done to learn how a spider will react to a synthetic web made of nylon filaments and how heat, noise and light influence web-building. As I have mentioned, most web spinners sense the presence of their trapped prey by feel. Those that make orb webs wait for a struggling insect to send a signal down the telegraph line in spite of the fact that bits of windblown debris agitate the line almost continuously. When a fly lands on the web, the spider immediately rushes to the scene. How does it recognize the prey? An amateur in England explained the mystery by touching the web with a tuning fork that vibrated at roughly the same rate at which a fly beats its wings. The critical frequency of vibration caused the spider to pounce at once!

"Although not all spiders spin webs, substantially all make silk, particularly when they are young. The silk functions as a primitive but effective form of aircraft for dispersing spiders much as the downy seeds of some plants are carried aloft and scattered by the wind. The young spiders rarely set sail in a breeze, however. They prefer to wait for a warm day of flat calm when thermal currents sweep upward. Then, when conditions are just right, they project a jet of silk into the rising air. The silk appears to solidify instantly and then the flight is under way.

"The eggs from which the spiders hatch are laid in a cocoon of silk. The shape and size of the cocoon vary with the species, as does the number of eggs, which ranges from less than a dozen to several hundred. I transfer the cocoon from the cage to a glass jar with a wide mouth and cover the opening with fine screening, usually a scrap of nylon stocking. Fine screening must be used because the young of some species may be no larger than the head of a pin. Eggs laid in the fall may hatch the following spring. The newly hatched spiders may remain inactive for some time. Eventually they crawl up the wall of the jar. On a day that seems promising I take the jar outside, place it on the grassy lawn, remove the cover and watch. According to the scientific literature, the young spiders may land hundreds of miles from their starting point. Spiders are found in Death Valley far below sea level and on Mount Everest at elevations above 20,000 feet. On dewy mornings in spring I occasionally spot strands of discarded silk in the grass of our local parks, remains that mark the landing sites of young that had migrated perhaps only a few yards.

"A group of investigators in Germany has demonstrated that the administration of certain drugs causes the Zilla x-notata, a spider that spins an orb web, to make errors that are characteristic of each compound. For example, when given marihuana, the spider leaves a telltale space between the frame of the web and the spiral strands. Benzedrine causes Zilla x-notata to weave an erratic spiral, and so on. This suggests that the spider can be used to help identify unknown compounds [see "Spider Webs and Drugs," by Peter Witt; SCIENTIFIC AMERICAN, December, 1954].

"I made the experiment by administering Librium to Aranea tepidariorum. Librium is a depressant that can be obtained by prescription at drugstores. The spider was allowed to spin its normal web in a cage. I then mixed one capsule of Librium in 10 drops of water. With a pair of forceps I gently removed the spider from the cage and held it still as I applied a drop of the solution to the area of its head with a medicine dropper. I removed the excess fluid after about a minute by touching the drop with the corner of a sheet of blotting paper and repeated the treatment at five-minute intervals. I applied an equal amount of tap water to the head of a second spider that served as a control. Both spiders were then placed in separate cages. The spider that was drugged spun a skimpy web; the control spun a normal web. Two days later the drugged spider was transferred to a third cage. It subsequently spun a normal web, indicating that the effect of the drug had worn off.

"Friends occasionally ask me about the possible hazard of experimenting with spiders. Everyone has heard about spider bites. I have never been bitten by a spider, nor has anyone I know. The risk must be small because we are all exposed to them constantly at home. I suppose the hazard varies with the locality. As far as I know the more venomous species are not usually found in the northeastern region of the U.S. According to the scientific literature, the venom of some tarantulas that are native to the Southern states can kill small animals. All entomologists agree that no chances should be taken with the black widow spider. This native of the Tropics is occasionally shipped north with bananas or other fruit. It is also found in Florida. The black widow has been known to put a horse out of action with a single bite. Although the risk of a spider bite is not great, if I ever get one, I'll have it examined by a physician."

Bibliography

THE SPIDER BOOK. John Henry Comstock. Doubleday, Doran & Company, Inc., 1940.

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