Discovering life

Activities

Ant lions
Aspirator
Caterpillars
Evolution simulation
Flatworms
Growing ferns
Keeping invertebrates
Keeping orb weaver spiders
Looking at leaf litter
Methinks tis like a weasel
Mosquitoes
Nematodes
Planarians
A plankton net
Pooter-making
Spiders' eyes
Terrarium making
Looking at dust
Looking at eggs
Small animal traps
Light traps
Other pages on this site

ideas


Breeding mosquitoes
You will need some large soft drink bottles, small sticks or twigs, some pond water, a commercial "complete fertiliser", like Zest or Thrive, and it would be nice to have microscopes, slides and cover slips, and especially Gurr's Water Mounting Medium (if obtainable). You will find out more about these items in a new page of microscopy ideas.

Get some pond water or water that has a greenish look about it, dilute it with tap water, and boost it with a small amount of fertiliser. Use this to fill the bottles about half full. Put a branching stick bottom-first into each bottle: once it is pushed down, it will spring out and provide a place for adult mosquitoes to rest.

Put the bottles in a bright sunny place for about a week. At the end of this time, there will be a good supply of living junk in the bottles, so it is time to collect some mosquito wrigglers, and add some to each bottle, then put a piece of gauze or fine material over the top and fix it in place with a rubber band. Observe the wrigglers at least once a day, and watch how they grow and change.

This will help you understand


Ant lions!!
These are my favourite animals, because they dig such neat holes. To keep some, you will need some sandy soil in a flat tray, a plastic cup, some ant lion habitats, and a supply of ants.

Ant lions live in sandy soil, under rock overhangs, beneath the eaves of houses, or under houses that are on piers, and so on. Get some dry sandy soil, put it in a flat tray, then hunt your ant lions. Look for small conical holes, about 1 - 3 cm across, in sandy soil in dry places.

Use the cup to scoop up the entire conical nest, and 2 or 3 cm of soil from underneath, and dump the whole lot into a bucket. Do this a few times, and take your sand back to the tray. Spread the collected sand out, and wait for a while: soon you will see the ant lions start to dig new holes.

Let them go without food for a day or two, and then make up some sort of an ant trap (a test tube with a small amount of treacly sugar solution or "Vegemite" works well). Leave the trap near an ant nest. When there are a few ants inside, pick the tube up, and seal it, and take it to the ant lion tray.

By now, the tray will be looking like a lunar landscape, with little pits where the ant lions are. Release a couple of ants in the middle, and watch what happens. Ant lions grow up into beautiful lacewings which destroy aphids, so keep feeding them until they develop into adults, or release them back into the wild.

This will help you understand. Or if you prefer, try this remarkable link to find out all about ant lions around the world.


Making a pooter
This is a simple and safe pooter or aspirator. I developed it with the help of some teachers who were visiting the Australian Museum one day, and Carrie Arkinstall (now Carrie Bengston) drew the picture for me. The standard form uses glass jars and glass tubes, and it is intended for adult use in collecting small animals.

You will need some 3 mm clear plastic tubing from a hardware store, a clear plastic film canister (talk to your friendly local photographic shop and you should be able to scrounge some of these), some sticky tape and a piece of fine cotton cloth, like a piece of an old handkerchief.

Drill a tight hole in the lid, and another in the bottom of the container (I usually use a 13/64" drill bit -- start small and work up). Push a 4 cm length of tubing through the bottom hole and a 20 cm piece through the hole in the lid. Sticky tape a piece of cloth over the inside end of the lid tube, and clip the film container together. Now you are ready to go out and catch small animals.

This will help you with ideas


Finding nematode worms
Some nematode worms are large enough to be seen without a lens or a microscope, but most of them will require that extra piece of help. Still, you never know your luck!

You will need a funnel, preferably made of glass, something to stand the funnel in, a piece of rubber tubing about 6 cm long, a burette clip or a strong spring clip, some water, a face tissue, and some soil samples.
It would help to have a microscope and a supply of slides and cover slips.

Attach the rubber tubing to the lower end of the filter funnel, fold it over, and seal it shut with a burette clip or spring clip. Set the funnel up on the retort stand with the ring clamp, and pour in some water until the stem of the funnel is full. Then wrap your soil sample in a face tissue, place it in the funnel, and carefully add more water, until the sample is more or less covered. Leave it for several days.

This will help you understand


Keeping invertebrates
No matter what insect or invertebrate you care to study, there are always questions you can investigate: what temperature range does the animal prefer, what humidity level, what food does it prefer, what senses does it have, and what can it detect with those senses, how do the animals communicate with each other, what are the best breeding conditions, or what stimulates it to breed, and so on. Just choose your animal and enquire!

You will need to provide food and shelter, some safe water to drink, and you will generally need to make sure the animals cannot escape. That means an invertebrate-proof container of glass or gauze, and some way of getting into the container without anything getting out. (A friend of mine established a green ants' nest in a Museum, and found the only way to stop them climbing out was to smear the whole of the access hatch with Vaseline.) Orb-weaver spiders will build webs on a wooden frame that is sitting over a large flat dish of water, but you have to watch out -- if a breeze carries the first threads away to something outside, the spider can escape!

Safe water means something the invertebrates will not drown in: sometimes what you need is an inverted glass tumbler, sitting on a circle of face tissue, sitting on a saucer.

The other main rule is to keep the population levels low. For example, take ONE caterpillar from a bush, and give it a small twig, sealed into a tube of water, to eat the leaves from. As you will read in the next section, even butterflies are smart: they lay eggs on the trees their caterpillars will like to eat.

This will help you understand


Keeping caterpillars
Many caterpillars are fussy about what they eat. It is safest to assume this applies to your specimens. Whatever plant you find them on, that is their choice, so make sure they have some leaves from that plant to eat. First set up your container, with some soil or sand in the bottom, and a beaker with water in it.

Cut a piece of gauze to almost cover the beaker, with a small hole to stick food plant pieces through. Then collect your specimen caterpillar(s), but don't be greedy: two of any one species should be a maximum. Avoid handling them: it will be bad for them, and may also be bad for you. Take a small branch from the food plant, put the end in water, and wait. Replace the branch every few days and watch your caterpillars carefully.

Photograph or sketch them moulting if it happens, the caterpillar itself from time to time (note the dates!), the pupa, and the final product. Mount these as a display: and the adults can be released. You will need to make sure that the emerging adult has enough room to spread its wings right out.

This will help you understand


Getting the animals out of leaf litter
Leaf litter is the valuable stuff that is on its way from being part of a plant to being part of the soil, and going back into new plants. Leaf litter is a collection of decaying leaves, twigs, petals and bark, all the bits that fall from dead plants, and it is the home of thousands of small animals, and millions of bacteria and fungi in every square metre.

The standard method of extraction of leaf litter animals involves a heat source, usually a light globe, above a leaf litter sample sitting on gauze, and with some sort of cover to stop the litter drying out too soon. The most common arrangement is a filter funnel, with a small piece of wire gauze near the bottom, a leaf litter sample, and a "clock glass" over the funnel top, and immediately below a 25 watt light bulb.

I have used and made a number of variations on this apparatus over thirty years, and one of the simplest is a PET bottle with the bottom sliced off. I put a standard scientifically assessed handful of leaf litter on a piece of plastic "flywire", slip that into the upturned bottle, and then sit that in a white ice cream container. Even without heat, huge numbers of animals fall out over the next 24 hours, and some keep falling for up to a week.

The method you use is up to you.

And here is a project idea


Making a terrarium
Note: this is more of a "how to" than a real experiment -- make up your own!

You will need a fish tank which does not leak, gravel, sand, access to plants. Use small plants: mosses and such go well. I like to add the odd fern and any small weedy-looking shade plants. Collect small samples of moss when you are out and about, dividing the collection into three parts to place on the slope which is described below, at three levels (so they can thrive in the best environment). The common club moss, Selaginella , also does well, and so do violets.

Use a daylight electric light (aquarium shops!) or place near sunlight - which is why shade plants are a good idea. Set up a small fish tank with washed sand on a 10 or 15 degree slope along the length of the tank, ending about 5 - 10 cm short of one end. Lay the sand on a gravel base about 2 cm deep. Damp the sand and pack it down: the excess water runs down and along to the sand-free end and pools there - you can grow duckweed and algae in the water, plus really great green slime for microscopy.

Then plant mosses, bryophytes, Selaginella , weedy things and small ferns, up and down the slope, and maintain the water level. Add a few river pebbles as part of the land surface in the terrarium to provide more niches - granite goes well in the water. After that, just keep adding bits and pieces and ripping out any plant that runs away. Water the system by leaving an upside down PET soft drink bottle sitting on a rock at the lower end, which keeps the water level constant over a long period of time. Very useful during holidays and such, but you will probably want to cover it all in cling wrap as well, at least over the summer holidays, as the PET bottle is good for a fortnight in fairly direct summer sun with no cover but flywire.

Occasionally, water gently up and down the slope with a watering can to maintain a bit of variety, and to help the mosses and ferns which need free water to breed in their attempts to replicate.

When the arthropods get too populous in the tank, I send in a few spiders. You see, the tank at home doubles as a guest house and recovery room for semi-drowned frogs, so it is covered in fly-wire to keep the humidity down, and there is a hole in the fly-wire at one end. An up-ended de-bottomed PET bottle (makes a great funnel!) goes through a small hole in the fly wire on top of the tank - I put leaf litter in this funnel, and the beasties just migrate down and fall into the tank.

When there are no frogs in residence, the spiders clean up nicely - use the household "Daddy Long Legs", spider found around the world -- the one with a long slim body ( Pholcus phalangioides ) or in the north of Australia, the one with a globular body. We had a centipede for a while, but millipedes are vegetarians, and the centipede did not do all that much, either.

The flywire doesn't come off under the weight of the PET bottle funnel, as I have shaped it like the lid of a shoe box and then stitched it into that form with a stapler - you just lift it off when you want to garden, or add some new bits of moss, fern or whatever. The flywire also keeps the spiders in and the mossies out.

There are some more hints here


A plankton net
A plankton net like this can be used to sample small animals swimming at or near the surface of the sea, or floating in that area. The main parts of the design are a towing line to pull the net along, a swivel to stop the line kinking as the net spins while it is being pulled, three lines attaching to the net, a stiff hoop to hold the net open, a very fine net, and a small glass bottle which attaches to the lower end of the net.

As the net is pulled along, any animals which are trapped by the open mouth will be pushed down to the end, where they will be largely protected from damage by the still water in the glass bottle. You can buy nets like this for a high price, or you can make one.

The towing line can be a fishing line: I have used a fishing rod to haul a net like this through the water while walking along a wharf or jetty, or out to one side of a boat which is being pulled along by a 2 hp motor. The swivel is standard fishing tackle, available from any shop that sells such equipment. The hoop can be a length of coat hanger wire, bent into a circle, the mesh can be the leg of a stocking, either sewn over the hoop, or glued to it with contact adhesive. If possible, attach the bottle by attaching a metal screw lid at the far end of the net, so that you can change bottles regularly.

Nets like this can also be hauled through seaweed and water weed to sample the small animals living on those plants.

This will help you with project ideas


Keeping orb weaver spiders
The actual size of this frame is not all that important, so long as it will fit into a large water dish of some sort. You can make the frame from 2" x 1" (41 x 19 mm DAR in metric countries) timber, and make sure that you have a hole drilled in the underside of the top rail for the spider to shelter in during the day. You may wish to place the whole arrangement in a mesh cage so you can release small flying insects, or you can carry the whole arrangement out of doors at night, and place it near a light until the spider has enough food, though some species I have tried this with went and sulked when they were carried around.

Build the frame to fit a large water dish, drill the hiding hole, catch a spider in a jar and release it on the frame over water, and after a couple of days, it should spin a web for you. After you have studied it, let the spider go near where you found it.

Here is some more information


Dust
This needs either a microscope, or a good hand lens, as well as some clear sticky tape. You can sample dust from all sorts of places, just by pressing a piece of sticky tape onto a dusty surface, to collect a sample of the material that you found there.

This will help you understand


Looking a spider in the eye
You will need a hand lens or a dissecting microscope for this. Spiders have strange arrangements of their eyes, especially jumping spiders (Salticidae). These are small spiders which do not make webs, and they have strong legs: they are usually brightly coloured, and they have a distinctive square face with two large eyes.

The problem with spiders is that many people are uncertain which ones are dangerous and which aren't, so the best thing to do is to catch your spider in a small container such as a jar, examine it, and then let it go.

Professional spider fanciers (arachnologists) can use the eyes to identify a spider family in many cases. Explore your local spiders, and see what you can discover.

This will help you understand


Methinks 'tis like a weasel
This one requires access to a form of BASIC, or the ability to translate some fairly simple code. I have used QBASIC which was packaged in DOS 6.22 for my programs. I note in passing that Richard Dawkins created his own first version in BASIC, and later translated it to PASCAL. I hope this code is sufficiently annotated to help you translate it.

In The Blind Watchmaker , at about page 46 - 49 in the Penguin edition, Richard Dawkins describes the sort of program that generates the phrase "Methinks 'tis like a weasel" from random letters. Remember the infinite number of monkeys, on an infinite number of typewriters, all typing away, and one of them producing the complete works of Shakespeare? This is a more modest attempt to generate just one line from Hamlet, spoken by the Prince of Denmark to Polonius.

Here is my first attempt, ready for you to play with: it all lies between pre-format tags, and can be neatly copied and pasted into a file called WEASEL.BAS, ready to run. A few comments first: as I ran this, I found that the system started to undo itself, so I put in a conservatism factor, and I soon added limits to generation size and generation number.

Next I set up the target string (as you will see, this is directed mutation, where some mutants have a distinct advantage), a set of blanks and a full alphabet set plus blanks, and created a set of letters from Z$(1) which is "a", all the way down to Z$(27) which is a blank.

From there, it is simply a matter of creating random strings, comparing them with the target, choosing the best, mutating that, selecting again, until the target is reached. It is most instructive to try different values for "bias" at the start of the program. BaseParameters:
bias = .96: REM: this is the conservatism
size = 100: REM number in each generation
rounds = 100: REM: maximum number of generations

TheStrings:
x$ = "methinks tis like a weasel": REM this is the target phrase
limit = LEN(x$)
best$ = "--------------------------": REM: this will be the best version: it is a blank string to begin with
set$ = "abcdefghijklmnopqrstuvwxyz ": REM alphabet plus blank
n = LEN(set$): REM count the number of letters we will have
DIM z$(n)
FOR i = 1 TO n
z$(i) = MID$(set$, i, 1): REM give each letter in the set a label
NEXT i

max = 0
DIM animal$(size): REM these are the "animals", and a DIM statement makes sure we can label each one
DIM evolved(size): REM: this is their "fitness" or match with target, one per "animal"
CLS

stringset:
FOR i = 1 TO size
animal$(i) = best$
NEXT i
REM: new generation all the same as the best of the previous generation

Mutate:
RANDOMIZE TIMER
FOR i = 1 TO size
FOR j = 1 TO limit
chance = RND: REM: will we mutate or not?
pick = INT(RND * 28): REM choose a letter: REM next line is a LONG one!
IF chance > bias THEN animal$(i) = LEFT$(animal$(i), j - 1) + z$(pick) + MID$(animal$(i), j + 1, n - j)
NEXT j
NEXT i

Evaluate:
FOR i = 1 TO size
v = 0
FOR j = 1 TO LEN(x$)
IF MID$(animal$(i), j, 1) = MID$(x$, j, 1) THEN v = v + 1
NEXT j
evolved(i) = v
IF evolved(i) > max THEN best$ = animal$(i): max = evolved(i)
NEXT i

count = count + 1
PRINT best$, : PRINT max; " matches", : PRINT count; " generations"
IF count > rounds THEN END
IF max < limit THEN GOTO stringset

Why bother to mess around with things like this? Well, if we accept that even slight improvements can be retained in a population, we get some idea of how evolution works.

This will help you explore this further


Collecting flatworms
Small freshwater flatworms can be almost anywhere. They are small worms, mostly under a centimetre long, although land planarians can grow very much larger. Freshwater flatworms can regenerate when they are chopped in half. I have a small drain to collect water that seeps into my backyard, and half-way along, I have a pit, designed to catch any silt that washes in. This is under a meshed grille, to keep mosquitoes out, and the flatworms live in the mud and water in the pit: all I have to do is scoop them out.

To find them in a lake, swamp, pond, puddle or small stream, scoop up a cup of water and mud, and add it to a two-litre plastic bottle, or a flat white dish, and repeat. Put a couple of centimetres of water and mud into the dish, or fill the bottle almost to the top, then leave it to stand. Use a modified eye-dropper or a pooter to pick the worms up, once the mud has settled out, and the worms have started moving.

Note: if your water source is at all suspect, use an eye-dropper!
Note: if your water source is at all suspect, use an eye-dropper!

Our eyes are conditioned to spot movement and the worms show up well in either a clear bottle or a white dish. Use the pooter to transfer them to a small dish, and from there into a third dish: by now, you will have left most of the mud behind. I find that it helps to clear a strip of mud from the centre of the dish, and use a pooter to lift them. The traditional food for planarians is small pieces of liver, but I find they are also attracted by a sliver of cheese dropped into the dish.

I have yet to try this, but you may also have some success in dangling a small piece of raw liver (or cheese) in a suitable area on a piece of string, pulling it up after half an hour. (Later: One of my reference books suggests beef liver or the yolk of a hard-boiled egg, tied in cheese-cloth as an effective bait.)

This will give you some ideas for further enquiries


The chemistry and physics of eggs
You will need an egg or two, some vinegar, and some treacle (also called golden syrup or molasses).

Put some egg in a glass, then add enough vinegar to cover the egg, and then leave it to stand. You will notice bubbles coming off the egg as the calcium carbonate shell dissolves in the acidic vinegar.

If you leave the egg in the vinegar after the shell is dissolved, you will see an interesting effect. If you put the egg into a strong solution of treacle and water, this effect reverses.

This will help you understand


Making an insect trap
You will need PET drink bottles, foods to use as bait.
Use any sort of bottle or jar with a small opening, and try a variety of baits: banana or banana skin, honey, sugar and "Vegemite", Marmite or beef soup (good for blow flies!) are all traditional favourites.
You will also need suitable tools for cutting the bottles, and making holes in them, and you will need a suitable place where your traps will be left undisturbed for several days.

What you can investigate

  • How effective a fly-trap can you make?
  • Which baits are the most effective?
  • Work out why some baits are better for some animals.
  • Would you expect to keep on catching the same species over a period of two weeks? Test your hypothesis, and then make your fortune, applying what you learn.
  • Set out a number of traps, side by side, using different baits, or using the same bait, but different designs.

This will help you with methods


Light traps
You can make an effective insect trap with a funnel, a light with a shade and a jar. The jar should have paper around it, so you can unwrap it to look, but so no light can get out, and the shade and funnel should be opaque.

This means the only line of access for the insects attracted by the light is along a path that leads them into the funnel, and so down into the jar. You can adjust the gap between the shade and the funnel, so as to keep out larger insects.

Two challenges for you:

  • Can you make a trap that attracts mosquitoes? Experiment with different coloured lights.
  • Using mains power outside is always a bit risky. Build a trap using a 12-volt bulb, and while you have a 12-volt DC supply in the area, set up a system with a fan or fans from old computers, which usually use a 12-volt source ( check and check again! ) to blow or suck the animals down into the trap. Your problem will be to stop the insects getting caught in the fan -- I know of at least two solutions.

This will help you use this trap humanely


And now for some help

What the mosquitoes are doing
Mosquitoes are filter feeders as larvae -- I don't know whether the tumbler stage (pupa) eats or not, but maybe you can design a neat experiment with distilled water to find out.
According to my reference books, the adult females that hatch will not lay eggs without feeding. This is not my experience: try it, and see if you get a second generation of wrigglers, as I always did.
Live specimens can be mounted successfully in ®Gurr's Water Mounting Medium, which slows them down for microscopic examination, while allowing observation of movements of the gut, breathing tubes, and so on. Adult specimens can also be mounted in this medium: can you tell a he from a she?

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Ant lions!!
Ant lions are the larval stages of lacewings, and they prey on small insects. Mostly they eat ants, but I have also seen one eat a small weevil. The ant lion has a large head, with a formidable (to an ant!) pair of nippers. It burrows into loose dry sandy soil and then throws sand up with its head, making a small conical pit. Then it sits at the bottom of the pit, waiting for something to come along and fall in.

The dry sand is at the angle of rest for sand, around 30 degrees for spherical grains. If anything blunders over the edge, it and a small amount of sand, tumble to the bottom of the pit where the JAWS are waiting. If the ant escapes, the sides of the pit fall down, carrying it down again, and all the while, the ant lion is tossing more sand up out of the pit: some of that rains back down, pushing the ant back to the bottom. Soon the ant is seized, and pulled under the surface, where its body juices are slurped out. Then the dried husk is flung out, and the ant lion waits for another meal.

If you want to buy some antlions, rather than catching your own, take a look at AntLionFarms.com who found this page, and asked me to add a link. They seem OK to me, so there's the link for you.

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How the pooter works, what to do
The pooter is used to suck up animals without them disappearing down your throat. That is why the piece of cloth is there.
You can use your pooter on leaf litter, or you can use it on a white sheet, hung over a line at night after rain, with a light at the bottom, or you can shake bushes over an upside down umbrella, and collect the animals that fall off with your pooter. When you have caught a few, tap them to the bottom of the container, take off the lid, and then shake them out.
The umbrella method works very well. Grab a branch, hold it over an upturned opened umbrella, and give the branch a firm shake. I usually carry an old black umbrella and a decrepit white umbrella in the boot of my car.

Probe

Wet pootering
Can you make a pooter that will work on small tadpoles? You will need to modify the design . . .

Survey Can you make valid comparisons between the small animals on different plants of the same species in different locations, or between plants of different species in similar locations? Which bushes do the small weevils favour, for example?

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How the nematodes get caught
During the waiting time, the nematodes will make their way down through the fibres of the tissue (they are mostly very small!), and they will shelter in the dark rubber tubing. Later, when you run off a small amount of water, you should have a sizeable number of nematode worms in the water to examine.

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The great litter hunt
How do the animals in your compost heap or leaf pile change during the year? Do some species come and go? How do they vary at different depths? Do some prefer damp litter while others prefer drier litter? Collect data, count individuals, record varieties found, over a period of six months or more. Can you relate the changes to any other factors, like the weather?

Your main problem in a project like this will be to keep the conditions as standard as possible, from one sample to the next, from the first to the last, and it is probably best to plot your results as floating three-week averages, calculated once a week. Aside from that, over to you :-)

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Terrarium secrets
I always carry a few film canisters when I go bush, as these are good to collect small water samples to drop in the bottom of the tank. Stir up a pool, scoop out a canister full, clip on the lid, and off you go - the loss of 10 mL or so never hurt any pool, and the additions prevent any chance of an equilibrium.

Crumble the odd bit of dried fern leaf over the lower end of the slope to release spores - you never know your luck, though I have better luck germinating fern spores on mud agar - boil up some mud, decant while hot, chuck in some agar (1.5 g per 100 mL), and plate it out. The fern prothalli can then be set in place where you feel like it, and watered now and then.

Another source for water for the pool in the tank: I keep three two litre apple juice bottles with a pinch of "Thrive" (a brand of "plant food" -- inorganic fertiliser) in each of them, on top of the tadpole tank, with duck weed, algae and the occasional dead leaf from a nearby creek to add sessile life forms. These bottles also get donations from the film canisters of water from time to time, and one of them has now got the cutest little flatworms running around in it. I will add some of them to the terrarium water shortly.

Time taken each week? About two minutes - plus the pottering time when I bring some samples home - maybe five minutes a week in all. But I spend longer just looking . . .

About having frogs in residence: we have a swimming pool, and frogs often fall in during wet weather. Frogs should not be kept in water: they are land animals which go into water, and if they stay too long, they get bloated with water that soaks in under osmosis . So we need to fish our frogs out of the pool, and dry them out in the tank -- so now you know why there are bits of stone over the surface, and plenty of animals in the area.

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Plankton project ideas
With suitable nets, you can explore the plankton types and densities over a time period: either looking for daily patterns, or monthly patterns (some plankton may respond to the full moon, so samples at 9 pm could be useful, or as the seasons change.

You could also just explore the types of plankton found in one place, or compare different environments at more or less the same time of day, over a period of time, to see if any observed changes are correlated, and whether any observed differences are maintained over long periods.

Aside from that, you have the tool, you have some ways of using it, so go for it!

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Keeping spiders
Studies you could undertake:

  • How long does it take a spider to catch a fly?
  • How many flies will a spider catch before it decides to take a break?
  • Does a spider prefer certain types of food?
  • Which threads of the web does the spider actually walk on?
  • How long does it take a spider to make a web?
  • How does the spider make its web?
  • What does the spider do with its old web?
The main thing to watch out for is that you store the spider and its frame somewhere away from drafts, as the spider will release a thread of fine silk if there is any breeze, and make an escape bridge if the floating thread makes contact with anything.

As I have indicated, the actual dimensions are not all that important, but the section where the web is to be made should probably not be smaller than about 40 cm from one edge to the other, or more than 60 cm. Choose a suitable spider from its web -- don't grab a tiny one and expect it to succeed on a huge frame. If you want to use the same frame for small spiders, drill a small hole in the bottom rail, and put a nice branching twig into it.

Probes:
When the web slopes, an orb weaver will always hang from the under surface. Does an orb weaver ever make a vertical web, and if it does, where does the spider choose to hang?
Many spiders in the orb weaver group have striped legs. Why might this be? How common is it?

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Dust
As a bare minimum, you are likely to get tiny food scraps, bits of the cases of dead insects, sand grains and an assortment of fibres. If you are using a microscope, you may be able to identify a range of pollen grains as well.

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Spiders' eyes


The most interesting spiders to look at will be the ones which hunt, not the ones who weave webs. Orb weavers can depend on a sense of touch to catch the prey animals which are caught in their webs.

The crab spiders (Thomisidae), for example, have two curved rows of four eyes. These spiders are often found lurking in flowers, waiting for an insect to land on the flower and provide dinner.

Some spiders which live mainly in dark places have "nocturnal eye", which are usually pearly white, but normal spiders have diurnal eyes, which appear dark or coloured when you look at them.

More interestingly, you can track down tiny spiders at night, by holding a bright tight-beam torch (flashlight to Americans) close to your ear, and sighting along the beam, searching for the reflections from their eyes. You can find even the most minute spiders this way.

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Methinks 'tis like a weasel
When I explored this system, I found that a conservative form of replication with low mutation levels took too long, so I messed around with the bias, and started with a low bias that increased over time, producing the code below, which is WEASEL4.BAS in my files. You get this one without explanation, except that I also gave the mutation system more chance of getting the more common letters of the alphabet, and I decided that maybe people would like to put in their own phrase.
BaseParameters:
size = 100: REM number in each generation
rounds = 100: REM: maximum number of generations
bias = .2: REM this is the conservation level for "genes"

TheStrings:
CLS
PRINT "Choose the Shakespearean phrase would you like": INPUT x$
REM: x$ is the phrase we will aim to achieve

lp = LEN(x$)

best$ = ""
FOR i = 1 TO lp
best$ = best$ + "-"
NEXT i
REM: this produces a string of dashes

limit = lp
set$ = " abcdefghijklmnopqrstuvwxyz aeiourstnmls etaoinshrdlu"
set$=set$+"abcdefghijklmnopqrstuvwxyz aeiourstnmlhtprst etaoinshr "
REM alphabet plus blank, built up over two lines to avoid splits in your display
REM this is closer to the normal letter frequencies found in English text
n = LEN(set$)
DIM z$(n)
FOR i = 1 TO n: z$(i) = MID$(set$, i, 1): NEXT

max = 0
DIM animal$(size): REM these are the "animals"
DIM evolved(size): REM: this is their "fitness" or match with target
CLS

stringset:
FOR i = 1 TO size
animal$(i) = best$
NEXT i
REM: new generation all the same as the best of the previous generation
bias = SQR(SQR(SQR(SQR(SQR(max / n))))) - .001

Mutate:
RANDOMIZE TIMER
FOR i = 1 TO size
FOR j = 1 TO limit
chance = RND: REM: will we mutate or not?
pick = INT(RND * n): REM choose a letter
IF chance > bias THEN animal$(i) = LEFT$(animal$(i), j - 1) + z$(pick) + MID$(animal$(i), j + 1, n - j)
NEXT j
NEXT i

Evaluate:
FOR i = 1 TO size
v = 0
FOR j = 1 TO LEN(x$)
IF MID$(animal$(i), j, 1) = MID$(x$, j, 1) THEN v = v + 1
NEXT j
evolved(i) = v
IF evolved(i) > max THEN best$ = animal$(i): max = evolved(i)
NEXT i

count = count + 1
PRINT best$, : PRINT max; " matches", : PRINT count; " generations"; bias
IF count > rounds THEN END
IF max < limit THEN GOTO stringset


Suggested studies, all requiring careful statistical analysis:

  • Which bias gives a result in the smallest number of generations?
  • Do smaller phrases require fewer generations?
  • What effect does it have to increase or decrease generation size?

For more on this, look at Ian Musgrave's pages on such things. Like me, Ian is a member of the ABC Science Matters List, and when this topic came up a while back, we decided to point at each other. We have since met each other and decided to keep pointing at each other. Readers knowing only one of us will be left wondering about this, which is as it should be. Everybody needs something to wonder about.

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Flatworms!
Flatworms are able to learn, according to the standard literature. They can detect a DC current from two electrodes attached to a 1.5 volt dry cell, and will line themselves up with it, but do not give them more than a few seconds of current, and make sure they do not touch the electrodes.

The flatworms can learn to anticipate this sort of "shock", if you flash a light at them, just before applying the electric current. You could create an interesting experiment here, testing to find the best interval for rapid learning, and the maximum interval between flash and shock that still produces learning, though your result will probably need to be estimated from a graph of results, using a line of best fit.

Flatworms will regenerate if you chop them in halves through the middle with a sharp razor blade. Both ends of the worm grow the missing end, and both ends of a trained worm are supposed to recall the lesson. Test this to see if it is true. It is also possible to split the "head" lengthways between their primitive eyes, and produce a two-headed planarian. This requires a sure hand.

People used to believe that an untrained worm which ate a trained worm that had been minced would learn faster, but this belief appears to have been wrong. Still, you could test it . . .

Planarians are said to be photonegative (could that be a basis for an experiment?), so they need to be kept in opaque containers with covers. Change the water regularly, and feed them once a week on chopped raw beef liver or hard-boiled egg yolk, and take out the excess food with a pipette after a few hours. Apparently they do not often reproduce sexually in captivity, but do occasionally produce orange "cocoons" that hatch out a month or so later. They also reproduce by fragmentation, as one of my worms appears to be doing as I write this up. Back to the details | Back to the index


The chemistry and physics of eggs
The egg shell 'dissolves' (see below) in the acetic acid solution that we call vinegar. After that, some of the water in the vinegar is able to seep in through the membrane that lines the shell. It finds its way in through a process that is called osmosis.

Osmosis involves water diffusing from a region of high concentration to a region of low concentration. When you dissolve something in water, there is less room for the water, and its concentration is reduced. So when you put molasses in the water, you change its osmotic pressure, so now water flows out from inside the membrane, and the egg seems to collapse. The flow stops when the level of dissolved material in the water inside the egg is the same as the level in the molasses solution outside.

Does the egg shell really dissolve? No, it does not! Dissolving is a reversible process, and this is a chemical reaction which produces carbon dioxide gas. You cannot get the egg shell back by evaporating the acid away, and a correspondent rightly chided me for saying this as I did. I hang my head in shame, but you will commonly hear palaeontologists talk of 'dissoving away' the matrix that surrounds a fossil, using acid. Back to the enquiry | Back to the index


Insect traps
One of the more interesting fly-traps uses a PET bottle with a hole drilled in the side, and the neck of a second PET bottle screwed into the hole (you can use a hole saw, mounted in an electric drill, to make the hole in the side, if you fill the bottle with ice and freeze it first). Bait is added, and if you are after flies, covered with water, to make sure the flies drown.

I have used these in a swamp, with meat and bread as baits, and had rather interesting results.

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Light traps
The main thing to remember is that you need to check the jar regularly, and either release the animals or kill them. One or two large animals, and the smaller ones will be battered to pieces, and moths begin to lose scales from their wings as soon as they start fluttering against the sides of the jar.

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For similar material, see Microscopy ideas
This file is http://www.ozemail.com.au/~macinnis/scifun/live.htm, first created on August 19, 1997. Last recordedrevision (well I get lazy and forget sometimes!) was on February 11, 2002.

Worried about copyright? You need to go look at my fine print. Well, maybe you don't after you read the next paragraph, but do it anyhow . . .and to see some more ideas, look at the start of that same page

©The author of this work is Peter Macinnis --macinnis@ozemail.com.au, who asserts his sole right to the product as it is packaged here, recognising that many of the ideas are common. Any non-profit educational or home use is completely acceptable without let or hindrance. Copies of this whole file or site may be made and stored or printed for personal or educational use.


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