ABOUT THIS ISSUE
Published by Emporia State University
Prepared and issued by The Division of Biology
Editor: Robert J. Boles
Editorial Committee: Gilbert A. Leisman, Tom Eddy, Robert F. Clarke, John Ransom
Online format by: Terri Weast
The Kansas School Naturalist is sent upon request, free of charge, to Kansas teachers, school board members and administrators, librarians, conservationists, youth leaders, and other adults interested in nature education. Back numbers are sent free as long as supply lasts, except Vol.5, No.3, Poisonous Snakes of Kansas. Copies of this issue may be obtained for 25 cents each postpaid. Send orders to The Kansas School Naturalist, Division of Biology, Emporia Kansas State College, Emporia, Kansas, 66801.
The Kansas School Naturalist is published in October, December, February, and April of each year by the Kansas State Teachers College, 1200 Commercial Street, Emporia, Kansas, 66801. Second-class postage paid at Emporia, Kansas.
"Statement required by the Act of October, 1962: Section 4369, Title 39, United States Code, showing Ownership, Management and Circulation." The Kansas School Naturalist is published in October, December, February, and April. Editorial Office and Publication Office at 1200 Commercial Street, Emporia, Kansas, 66801. The Naturalist is edited and published by the Kansas State Teachers College, Emporia, Kansas. Editor, Robert J. Boles, Department of Biology.
* Dr. John Ransom wrote the section on microscopic organisms. He is Professor of Biology at ESU, where he teaches a highly successful course entitled GB 303 - Field and Laboratory Biology, where elementary and prospective elementary teachers are taught many laboratory exercises that may be used in the classroom.
** Dr. Robert Smalley wrote the section on "slugs". He is Professor of Chemistry at ESU. As a biochemist, he has worked with a number of kinds of animals. His research with slugs lead to the development of a way of growing the invertebrate in the laboratory. Trying to raise these curious animals will no doubt be an interesting experience for the science teacher. as well as the students.
Man is but one of over a million and a half different kinds of animals that have been identified on Earth. Some of the animals among this great variety of living things make excellent subjects for study.
It is best to take the class to see the animal in its natural surroundings. Unfortunately, this is not often possible. On the other hand, many kinds of animals can be brought into the classroom where the students may study them in some detail. It would be wise to contact your local Game Protector as to what animals may be kept in cages in the classroom. Some, such as migratory birds like the cardinal and robin, are strictly protected by State and Federal laws. This issue of the Naturalist suggests ways to keep several kinds of living animals in the classroom.
The interest span of people, especially children, is usually rather short. Animals should be released as soon as the children have had the opportunity to see the animal, study how it eats and acts, and to learn something of its life cycle. Turn the animal lose before the children start to neglect it, since the care and feeding becomes a "bore".
Wild mammals and birds should not be kept in cages for more than a short time, unless they are the "tame" varieties, such as hamsters, gerbils, and parakeets. When you release an animal, let it go at or near the place of capture as you can.
Use the simplest cage possible for elementary students. A glass jar covered with gauze netting of fine-mesh wire may be used for invertebrates, such as mealworms, moths, spiders, and ants. Even mosquito "wigglers" in water make interesting "pets", and help the student to grasp the concept of complete metamorphosis. A small roll of screen wire, set in plaster-of-Paris and the open end covered with an aluminum pie plate, makes a good cage in which moth pupae and butterfly chrysalises may be placed to watch the emergence of the adult stages. Information for raising various animals in the classroom will be presented later in this issue of the Naturalist.
Cages for rodents must be of wire, or metal, as the rodent (e.g., a mouse) may gnaw its way out of the cage.
Only a few birds may be legally kept in the classroom, such as the so-called "tame" birds (e.g., parakeets, canaries), as well as domesticated fowl, like small ducks and chickens. Care should be exercised in bringing the latter into the classroom (such as around Easter time), as they may be the source of possible
infection of the children with microscopic organisms causing unpleasant upsets of the digestive tract.
Be sure the cage is large enough for the birds or other animals to get sufficient exercise.
One of the biggest problems is keeping the cages clean. The bottom of all large animal cages should be
hardware cloth or hail screen, coarse enough to let the animals' wastes and feeding debris fall through. Old
newspapers or sawdust may be placed under the cage and replaced each day without opening the cage and
disturbing the animals inside. Be sure to emphasize to the children that clean cages mean healthier animals, as well as reducing odor in the classroom.
Large mammals must be kept in a large, strong cage (a few may be kept securely chained). Inform the children that it is not legal in most cases to keep opossums, skunks, squirrels, and other wild animals as pets, unless you have a special permit from the State Fish and Game Commission. Check with your local Game Protector and see if special arrangements may be made to keep such animals for a short time under his supervision. Release the animals as soon as the students have had a chance to observe and study them for a short time. Even the most appealing baby wild animals grow up to become an unpredictable, and sometimes dangerous, "pet" as an adult. Be sure to caution your students never to pick up a wild animal, such as a bat or skunk, that appears ill or to have lost all fear of man, as they might possibly be carrying the dread disease rabies ("hydrophobia").
Of all the mammals, mice are probably the best fitted for cage life. There are many kinds of mice that may be kept in the classroom and studied by the students. The common white (albino) mouse, from which the trait for wildness has been bred out, is the safest kind for a child to handle. If uninjured, they seldom bite the person handling them, and they do not usually dash away and hide when released outside the cage. Perhaps the most objectionable feature is the musty, sometimes offensive, odor they produce. On the other hand, white-footed mice or deer mice have very little odor, but are not easily tamed and tend to scurry away and are hard to catch if they escape from the cage or the person who is working with them.
Cages may be made from screen wire or small-mesh screen (e.g., 1/4-inch mesh). Larger mesh screen may let the mice escape, as they can squeeze through a surprisingly small opening. As field and deer mice are nocturnal, their activities will be more easily observed if the cage is covered with red cellophane. The mice will then be active during the daytime.
Be sure there is a constant supply of water present. Food may consist of various grains, nuts (e.g., unsalted peanuts), bread, and vegetables. An exercise wheel makes an interesting addition. A large phonograph record, placed on a center at a slant offers an interesting variation of the exercise wheel.
Meadow mice ("voles") may be captured under straw piles or flat rocks. However, they are not as tolerant of
crowding as are white-footed and deer mice, and may eat on each other if too many are placed in the same cage or pen.
All rodents have gnawing teeth (incisors) that grow throughout the life of the mammal. Some hard objects,
such as unshelled walnuts, may be put in the cage to provide something for the mice to gnaw on, and help them keep their incisors worn down.
Students may find bats, especially in the spring, and bring them into the classroom. Sometimes they will find a female with several young clinging to her, unable to get off the ground due to the combined weight of the young bats and the many insects they have consumed during the night.
It is best to handle the bat with heavy gloves, as they may bite with their tiny sharp teeth, and they have been known (as mentioned earlier) to be involved in the transmission of rabies.
Most bats are difficult to keep in the laboratory for any length of time. However, observing one for a day or two in the classroom can be quite informative. Have children note such things as the wings (it is the only mammal that really flies), the tiny claws on the tips of its "fingers", the size and shape of its ears, and how it eats. You may get it to take mealworms or other insects held up to it by a pair of tweezers. Give it water by means of an eye dropper.
Explain to the children that, contrary to what some people think, bats do not get into and snarl up a person's hair, they are not vicious, they are not mice with wings (look at their front teeth), nor are they blind. Note also the silky, soft fur, and the soft webbing that makes up the membrane between the wing bones.
Students will not be able to hear the "sonar" of the bat, but explain to them the bat's use of sound in avoiding objects when in flight and in capturing food while on the wing. You may wish to assign them the problem of looking up information about the many bat species found over the world, and have them make reports in class to the other students.
Only a few kinds of birds, outside of domestic types (e.g., chicks, birds purchased at pet stores, ducks, etc.) may be legally kept in the classroom. English sparrows, starlings, crows, and pigeons may be kept for study and observation. It is a great temptation to bring baby birds that may have fallen from the nest to school in hopes of raising them. However, intelligent as we humans are, the baby bird nearly always receives better care from their parents than we are able to give them.
If poisonous snakes are kept in the classroom, the door should be secured with a lock.
Be sure the bird cage has plenty of room. The wire should be of small mesh to reduce the chance of injury. Water should always be present, as well as perches so that the birds are off the floor of the cage. The screen at the bottom of the cage should be coarse enough to permit droppings to fall through upon a newspaper spread out below. The paper should be removed each day and replaced with a clean one.
Seed-eating birds, such as sparrows, must have grit mixed with the feed so that the gizzard may use it in grinding the seeds. Cracked corn, milo, oats, or sunflower seeds may be used as food, or you may get a sack of premixed bird feed from a local store.
Place the cage in a place in the classroom where the birds are out of drafts, especially in the winter. Release any native birds or move them to another classroom for additional study by other students as soon as the children become uninterested or the feeding, watering, and cleaning the cage becomes a chore.
Snakes are fascinating to most people -- even those who do not profess a liking for them. They are one of the easiest and cleanest animals to keep in the classroom. Though most snakes will readily accept food, you may happen to get a specimen who refuses to eat in captivity. Such snakes should be released, preferably where they were collected, or in a similar habitat. Do not release snakes just any where, especially where there are many people. Many people will kill a snake on sight, even though its feeding activities may be very beneficial to man.
Snake cages need not be fancy or elaborate. A glass aquarium with a hail-screeen top (weighted down) makes a good cage for most non-poisonous snakes.
Cover the bottom of the cage with something like wood shavings, pine needles, or even shredded paper. An inch or so of coarse sand, along with a rough rock or brick, will help the snake crawl out of its old skin when it is time for it to be shed. Some snakes, such as the blacksnake, like to climb branches, so it is a good idea to place a sloping stick in the cage.
Be sure water is present at all times. Some species (e.g., garter snakes and water snakes) may spend much of their time coiled up in the water dish. Even snakes of dry areas, such as rattlesnakes, will need a drink from time to time.
Snakes are cold-blood vertebrates, so do not "burn" their food as rapidly as a mammal. They may eat only one meal every few days, but it may be a "big one". For example, a bull snake may eat a mouse or two a day for several days, then refuse to eat again for a week or more. Remove any live mice that may be placed in the cage for food but not eaten in a short time. If not eaten, they may chew on the snake, or even kill it (this is true exen of rattlesnakes!).
Suggested food for some of the snakes that might be brought into the classroom:
Black snakes and Blue Racers -- insects (e.g., grasshoppers), other snakes, small mammals, frogs
Ring-necked snakes -- earthworms, insects, small frogs
Hog-nosed snakes -- primarily toads, but will sometimes eat frogs and insects
Bull snakes and Rat snakes -- mice and rats
King snakes -- primarily mice. Some species will eat other snakes, both poisonous and non-poisonous, insects
Water snakes -- fish, crayfish, frogs
Garter snakes -- frogs, toads, tadpoles, fish, large insects, earthworms
It is best not to keep poisonous snakes in the classroom, especially at the elementary level. If the science teacher has had sufficient experience to handle a poisonous snake, and if a strong, safe cage (that can be locked) is available, a copperhead or rattlesnake can be valuable in helping dispel some of the fear and misconceptions of poisonous snakes that many students have.
Snakes, being cold-blooded, must be kept in a warm environment if you expect them to feed or exhibit activity. When chilled, they become slow in their movements and refuse to take food.
Insist that students do not tease or molest caged animals.
You can tell when your snake is going to shed its skin, for the covering over the eyes (it is shed, too) will become a milky color. The cage should contain water and a rough stone or brick for the snake to rub against. In most cases it will crawl out of the old skin, which will peel off much as you might remove a rubber glove from your hand.
Some of the students may express a feeling of revulsion when the snake constricts around a mouse to kill it, and then swallows it whole. Remind them that this is an important part of the life of many animals. Ask them where the chicken came from for their fried chicken dinner, or the beef in their hamburger. Don't we humans kill and eat animals (or plants, if you are a vegetarian) in order to survive? Point out that the mice and rats that are eaten feed on the grains we need for our own food or for food for our livestock, and that they may sometimes spread serious diseases, such as the Black Death, or bubonic plague. In eating mice and rats, snakes render a very valuable service to man.
Lizards may be kept in an aquarium, which should be covered with a piece of hail screen.
A good place to keep lizards is in a dry, warm terrarium. A rock or piece of wood can be put in the cage to provide a place for the lizard to "sun" itself under a reading lamp. Fence lizards are fairly common, and usually eat well in captivity. They may be fed such things as mealworms, crickets, and small grasshoppers.
Though horned lizards ("horny toads") are appealing and gentle little reptiles they usually refuse to eat in
captivity. Their normal food is principally ants. It is a good idea to let the students examine the horned lizard, handle it gently, and then turn it loose back near where it was captured. In some states so many of these little reptiles have been picked up by tourists (usually to starve to death) that there are rather severe penalties for catching them and removing them from the area.
Most lizards need little water. However, the humidity of a classroom is often rather low, and so water should be provided.
Most turtles do not need to be kept in water. In fact, many forms live in places, such as semi·desert areas, where they seldom come in contact with water.
Do not paint your turtle, or purchase a painted one to bring into the classroom. The paint does not allow the shell to grow. This will cause the shell to become soft about the edges, and your turtle will die.
Perhaps the most easily kept, and the most "friendly" turtle is the box turtle. Most of them will accept food readily, and will consume earthworms, mealworms, crickets, pieces of meat (e.g., hamburger), as well as bits of apple and other fruit.
As with the other animals you bring to the classroom, release your turtle into a suitable habitat as soon as the students start to lose interest. Being cold-blooded a turtle cannot control its body temperature so do not release it during the cold of winter or it will probably freeze.
Salamanders, especially the tiger salamander, usually eat well in captivity. Larval salamanders, with their external gills, are especially interesting, as you may have the opportunity to see them metamorphose into the adult form. The larvae, if not too small, will eat small pieces of earthworm or bits of ground beef. The
larval stage may often be collected from small ponds by means of a minnow seine.
The adult salamander may be kept in a damp aquarium containing a piece of bark or a few flat stones under which it may hide. Be sure to keep the aquarium moist, as amphibians are poorly adapted to prevent the loss of moisture from their skins. Feed them earthworms or small insects, such as crickets or mealworms, every few days.
Wide-mourned gallon jar, laid on its side, and containing some damp spahgnum moss and a
piece of bark, make a good terrarium for a salamander.
Two rules to observe in keeping fishes in the classroom:
1. Do not overcrowd. A "rule of thumb" is to allow about a gallon of water per inch of fish.
2. Most people tend to overfeed their fish.
Several other rules to keep in mind are:
A. Cover the bottom of the aquarium with clean sand or fine gravel.
B. Plant a few aquatic plants in the gravel or sand.
C. Slowly add water to the desired depth.
D. Let the aquarium stand for at least a day before adding the fish.
E. Cover the aquarium at least partially, to cut down the rate of evaporation.
F. An aerator is not usually required if only a few fish are present and you do not overfeed. A small air pump and an air stone in the aquarium is just added insurance against the fish suffering from a low oxygen supply.
G. Keep the aquarium out of the direct sunlight. This helps keep the temperature of the water from becoming too high, and the algae (tiny, one-celled aquatic plants) from getting out of control.
Wide-mouthed gallon jars, "stocked" with a few guppies,
will let each student have his own little aquarium.
Some fishes do not get along well with each other. Most of the tropical forms sold in pet stores are suitable for use in an aquarium. Guppies are inexpensive, and let the children se a type of fish that gives birth to its young, rather than laying eggs.
Dwarf tropical catfish help to eat algae that tends to grow on the rocks and sides of the aquarium.
Tropical fish food is available in pet stores. Only a pinch each day is required. Do not feed more than the
fish will dean up in ten minutes. A few snails will help clean up any excess food.
Some of our native fishes are quite attractive, but are often overlooked as aquarium fishes. The male orange-spotted sunfish is a small, colorful individual, especially when in breeding colors. However, do not try to keep more than one male in a small aquarium, as they are quite territorial and aggressive. Several females may be placed in with the male. Small black bullhead catfish are hardy, and eat well in captivity. A few golden shiners or fathead minnows, which are available in most bait shops, also usually do well in the aquarium.
If your aquarium starts to "turn green", treat it first by scraping the algae from the glass, and setting the aquarium in a place with less light.
Box turtles are "friendly," easily kept reptiles in the classroom.
Change the water every so often. A good way is to put the clean water in a large container, which is then placed near the aquarium for two to three days. This lets any chlorine escape and the temperature of the water adjust to that of the aquarium. The fish can then be dipped from the aquarium to the container of clean water, the aquarium drained and cleaned , the sand and gravel washed and replaced, and the fish and the new water placed in the aquarium.
A small jar, with the open end closed with a wad of cotton, makes a "home" for fruit flies.
Insect collections are fun for children, as there are many kinds of colorful and interesting insect species.
However, insect behavior can only be learned by observing living insects, not dead ones, such as insects stuck on pins and placed in a box.
Fruit flies are good insects to use to study a type of insect with complete metamorphosis -- egg, larval, pupal and adult stages. Place a piece of ripe banana in an open jar. It usually doesn't take long before you will see the tiny fruit flies entering the bottle to feed and lay their eggs on the ripe fruit. As soon as a half-dozen or so flies are in the bottle, cover the top with a piece of cheese cloth, and fasten it down with
string or a rubber band. The eggs will be too small to see with the naked eye, but soon you may observe the tiny white, worm-like larvae feeding on the edge of the fruit. When the larvae reach a length of about one-fourth of an inch, they will crawl up the side of the glass, or onto a piece of crumpled paper in the jar, to pupate. The pupae are oval in shape, cream or brownish colored, and do not move. In about five days the pupal cases will split, and adult flies emerge. The entire life cycle in the jar will take about two weeks.
Mealworms, the larval stage of a grain beetle, are easily raised in the classroom. They may be secured from most any biological supply house, or some student who lives on a farm may find some among the grain sacks in the feed shed or barn.
The larvae are worm-shaped and have six legs. A five-gallon can (such as can be obtained from most any fastfood store, such as Vista) makes a good home. Place some bran or other grain product in the bottom and add the mealworms. It is a good idea to lay a piece of old gunny sack on top of the bran. Not only do the larvae like to get in the sack material when about to pupate, but pieces of apple and potato can be placed on the sack without getting the bran wet and causing spoilage. The larvae and adults will soon come to the apple or potato to feed, and may be collected for study or as food for such animals as turtles, salamanders, and fishes.
Crickets may be kept through the winter in a terrarium. Cover the bottom of a five-gallon can with a few inches of sand. Place a container of water in the can to keep up humidity, and some excelsior or shredded paper in which the crickets may hide. A low-sided water container (such as a Petri dish) will provide drining water. Crickets will eat dog food, bran, rolled oats, or even table scraps. They also need moisture, which may be supplied by sprinkling a little water over the excelsior or paper each day. If the crickets are able to
crawl up the sides of your cage, put an inch of vaseline or grease just inside of the top edge of the can. This will prevent their excape. Listen to the male crickets "singing". The rate at which they chirp can be used in making a close guess as to the temperature. Crickets also make good food for such pets as some snakes, toads, and turtles.
In the fall catch one of the large, colorful "orb-weaver" spiders, and place her (the male is small and inconspicuous) in a wire cage or a half gallon jar. The abdomen of the female will fill with eggs, and she will die after laying the eggs, encased in a silken cocoon. She will usually take mealworms, grasshoppers, and other insects readily up until egg-laying time, wrapping them in a trap of silken threads until she is ready to eat. The female spider may be allowed to crawl about on a student's hands without danger of being bitten. Do not attempt to pick the spider up between the fingers.
Another interesting insect to look for in the fall is the larval stage of some of the moths, sometimes called "wooly bears" or "wooly worms". These will often pupate soon after being brought into the classroom, using the "wool" to form a cocoon about the pupal stage. In the warm classroom the adult stage will often emerge by early spring, or before.
Euglena is the common, as well as the generic name, of a particular group of microscopic fresh-water organisms. They can be found all over the world in fresh waters. They are good representatives of the microscopic freshwater community and they can be easily cultured (maintained) in the laboratory. We could tell you a lot more about Euglena, but you should get your own culture going and discover by observation all of these things for yourself.
Clean a one-gallon glass jar and fill it 2/3 full of freshly boiled or distilled, water. Drop in eight grains of rice, cover, and let stand for 10 to 12 days. Stir up a stock of Euglena, fill a medicine dropper 1/3 full of the stock and shoot the water into your rice culture. Cover the culture and set it aside, out of direct sunlight. You should have a good, healthy, green culture in about four weeks. Observe it every day. When you have a good culture going, have each of your students make a slide of the Euglena from the culture and use the microscope to describe them by their observable properties.
You may obtain a small stock culture of Euglena from the Biology Department of your nearest college or
university, or from a biological supply house. Then, you will never need another stock culture again. If you get your culture going, you can use it to start new cultures every three to six months. All you will need are jars and rice. Never use more than six to eight grains of rice per gallon of water.
SLUGS IN THE CLASSROOM
Slugs are interesting, easily obtained and maintained, but rarely studied invertebrates. In the classroom they are much less trouble than mice and hamsters. They only require attention about once a week, and can be left unattended for several weeks. At first glance most people find them to be rather repulsive, but closer inspection shows creatures of great complexity and fascinating behavior. In this short article we will discuss how to capture slugs and maintain them in the classroom. In addition a few simple hints about studying them will be offered.
CAPTURE OF SLUGS
Two genera of slugs are common in Kansas. The small (about one inch) solid-colored Derocerus, and the large garden slug, Limax. Limax was introduced into the United States from Europe many years ago. Its size may exceed four inches and it may have dark stripes or it may be solid colored. For reasons which are not clear we find survival of Derocerus and solid-colored Limax to be much better than those with dark stripes on the body.
Slugs can be found just about anyplace. Look under logs in wooded areas, or under old lumber piles. Cellars of old houses, cisterns, and gardens are sometimes good places to collect them. Dog kennels are usually particularly good places to look. When looking for slugs keep in mind that they require moist conditions, and are usually most active at night. Best conditions are usually found for about a week following a heavy rain. In dry weather results in even the best collection sites will be disappointing. A hot, humid summer evening is ideal for collecting but slugs are active from early April until early November in Kansas. They are most readily captured using bait. Place some food (dry dog food, cereal, cookies, etc.) on paper plates near areas where you expect to find slugs. Check the pIates about every half-hour between dusk and 11 PM (or until you get tired). On good collection evenings in a good site as many as 70 slugs have been collected on 10 bait traps.
After picking up the slugs put them in a glass or plastic container which has some damp grass or moist soil in the bottom. A few small holes will provide necessary air.
Slugs are perfectly harmless, but the slime makes them unpleasant to handle. A pair of light gloves will make collections more pleasant. Soap and water will remove the slime from your hands. (An interesting class projects could be made on the subject of slug collections, studying such things as good sites, baits, different kinds of slugs collected, humidity, temperature, date, etc. A one or two year science fair project would provide valuable information about slugs for some interested student or group of students.)
HOUSING OF SLUGS
Slugs require humid conditions. The housing system may consist of a plastic or wooden box containing peat moss. The moss holds a large amount of moisture providing high humidity in the box.
A simple container sufficient for about 10 large slugs can be made in about 10 minutes. Obtain a styrofoam ice container from a discount store. Many sizes are available, but you should use one about 18x12x12 inches or larger. Put in two or three inches of peat moss (obtainable from a garden shop), and pour about a quart of water onto the moss. Place some pieces of wood or flat rocks on the moss to allow the slugs a place to hide. Put in the slugs. Put on the lid and fasten, tie, or weight it down. Place the container in a part of the room away from radiators or other beat sources. Your slug house is complete. To view tbe slugs simply remove the lid. Their slow movement renders esca pe of the slugs unlikely while the box is open. (see later for feeding).
If desired you can add a window to the slug container. Cut a hole in the styrofoam with a sharp knife and cover the hole with clear plastic (Saran, Handi-Wrap, Baggies, etc.) Tape the edges of the plastic wrap to the styrofoam using duct tape (obtainable from the hardware or discount stores), or other waterproof tape. If you wish, nonmetallic window screen can be used to cover the windows instead of the clear plastic.
Larger numbers of slugs can be kept in a habitat made from a wooden box. Old foot lockers, steamer trunks, cedar chests, etc. are ideal for this, and are readily obtainable at household auctions. Seal any holes with duct tape, and make sure the lid can be tightly closed. Cut a hole in the lid and cover it with safety glass, or thick, clear plastic. The plastic can be obtained from hardware stores in various sizes. Screen could also be used to cover the window. Add peat moss, water, rocks, wood and slugs. The system is complete. A cooperative shop class could build a very good habitat.
FEEDING OF SLUGS
Use dry dog food. We have used Bow-Wow, Gaines, or Purina. Presumably any good, hard food could be used. The dry food is placed in a plastic container. The use of a container is important. The food should NOT be placed directly on the moist peat moss, as it will very rapidly become moldy. Some mold always forms on the food even in the dry food container and does not appear harmful, but if large amount of mold is present slug survival appears to be reduced. Remove food which becomes very moldy. Experience will determine how much food to use, but a 5-pound bag of dog food will feed 10 large slugs for about a year. Potatoes, carrots, or other hard vegetables can also be fed if desired.
MAINTENANCE OF THE SLUGS
Add water when the peat moss begins to appear dry. Except for food and removal of an occasional dead slug (FLUSH IT) this is about all of the necessary routine maintenance. About every six months remove the slugs, and replace the peat moss. It may be more appropriate to simply pour out the moss, slugs and all at the end of a school year. Empty the container in a grassy or wooded area, but good public relations require that you not empty it near someone's garden.
The slug can easily be left unattended for Christmas vacation periods of two or three weeks. Wet the peat moss well and put an open bowl of water in the container. Remove all food to prevent mold growth. Place the container in some site where the temperature will be between about 33 and 70 degrees Farenheit, and leave.
If it is desired to keep the slug habitat over the summer it would be advisable to check, feed, and add water about every two or three weeks.
THINGS OF INTEREST ABOUT SLUGS
LOCOMOTION. Let a slug crawl on a piece of glass or hard plastic and observe it from the bottom. Look at the foot from the underside as the animal moves. Note the movement of liquid inside of the slug. It is not yet fully understood how a slug moves, but slime is necessary for movement.
SLIME. The slug has two kinds of slime, one for movement and the other for protection. The slime needed for movement is produced by a slime gland at the front of the foot near the head. The protection slime is produced all over the body. Scratch a slug gently with a small stick and note the production of slime.
The slime is mainly water with some sugar and protein in it. A slug can release as much as 20% of its body weight as slime in a few seconds if alarmed. To show this weigh a slug and drop it into a solution of laundry detergent in water. Notice the amount of slime produced. Remove the slug, wash it with fresh water, blot it dry and weigh again to get the weight loss due to slime release.
NOTE: This procedure may kill the slug if overly severe. If it dies you might wish to dissect it.
SENSE ORGANS. The slug has two pairs of tentacles. The upper (larger) tentacles have dark colored eye-spots on their tips. The lower (shorter) pair contain the animal's sense of smell. Touch the tentacles and observe their retraction. If tentacles are lost due to accident they regrow in a few weeks.
RESPIRATION. As the slug is lying still or moving note the large hole on the right side of the body. This is the pneumostome and is the "nose" of the slug, through which air exchange takes place. Touch it and watch it close.
SHELL. Slugs are related to snails, but have lost their outside shell. A shell is present but is inside of the body. You can feel it by pushing gently on the back of the animal just above the pneumostome. The shell has the function of protecting the heart. Remove and examine the shell in a dead slug.
REPRODUCTION. Slugs reproduce sexually, but both males and female sex organs are present In the same individual (they are hermaphroditic). As slugs crawl around you may sometimes see a rather long, light colored, membranous muscular structure coming from a hole near the front of the animal. This structure is the penis. In a complex (and rarely observed) process sperm are exchanged between two individuals. The young develop inside of eggs which are laid in large numbers. In the genius Limax each egg is about 1/8 inch in diameter and clear. A single slug may produce well over 100 of these eggs (the author counted 119) in an egg-laying process requiring several hours to complete. The smaller Derocerus produces 10-20 eggs each about 1/16 inch in diameter. In either species the eggs may be deposited on the surface of moss or under a rock or board. The eggs come out of a small opening on the right side of the head. As the eggs come out they are inside of thin slime tube which leaves them connected to each other with slime. The process of egg laying is relatively common to observe in the slugs (NOTE: In a newly established colony of slugs, egg production is rarely seen for the first month or so, but once started becomes quite common).
It requires about 20-30 days for the hatching process. The actual time depends on temperature, but 21 days is quite common. As the eggs develop the young immature slugs can be seen inside the egg after about 15 days. A small hand lens or dissecting microscope aids the viewer. After hatching the young slugs develop rapidly. In the authors experience sexual maturity has been attained within nine months in laboratory-raised Limax. It should be pointed out that many of the eggs which are deposited do not develop, thus you will not be totally overrun with slugs.
FEEDING. Slugs will eat just about anything. They scrape off the food with a ribbon-like rasp called a radula. If a slug is feeding on hard dry food in a light aluminum pan (cake pan) it is sometimes possible to hear the radula scraping as the slug eats. Pick up the pan with a slug which is eating and place it on a hard surface near your ear. If the room is very quiet the rasping sound can sometimes be heard.
RECYCLING OF DEAD SLUGS. Some slugs will die in your habitat. If Dot removed the other slugs may eat them. If not eaten they will simply decay due to bacterial action leaving only the shell after a few days. This can be a basis for talking to a class about the importance of the decay process. If a slug should escape from your habitat (it will happen) it will die very rapidly in the dry air of the room. You will find its dry, hard body on the floor. There is no odor from these escaped slugs.
In this short discussion a simple slug habitat and some simple things to do with the slug have been described. It is probable that the simple habitat could also be used for land snails, earthworms, etc., but this has not been tried.
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