Question: How are bees’ foraging patterns modified when they encounter nectar bonanzas?
Season: Fall, Spring (Winter).
Frameworks: II-3-C-ii (II-3-A-i, II-6-B)
Needed: This works extremely well with common lawn plants, especially Dutch clover (Trifolium repens) or any other clover. I would recommend Dutch clover in Spring or Fall. Other good lawn flowers that attract honeybees are Richardia brasiliensis or dotted horsemint (Monarda punctata) in Fall, and Florida betony (Stachys floridana) in Spring. The only special equipment needed is a syringe plus needle available from the school infirmary. For safety, the tip of the needle should be filed down, and the syringe should be used only by the teacher. The teacher must also mix beforehand a sugar solution near 30% by weight (1/2 cup sugar in 1 cup water).
Background Information: See Handbook pages 30-34 and 42-43.
How To Do It: Begin the activity without a lengthy introduction: students run out and start observing bees foraging. If watching clover, note that the clover “flower” is actually a head composed of many tiny individual flowers, each shaped like a pea or bean flower, and the bee visits several in turn. Whichever plant you’re watching, note that the bees do not visit all the flowers on a plant before leaving for the next. Why not?
After about three minutes of looking as a group, students split up. Each observes a bee (or series of bees) for at least 10 minutes. Each student records the number of flowers/plant (or florets/head, in clover) visited by the bee before it leaves. Students also record the bee’s next stop. Does the bee stop at the next closest head? or does it skip over the nearest head and go to the next nearest? or the third nearest? Anyway, students will tally whether the bee goes to the 1st, 2nd, 3rd, etc. nearest of those neighbors in the direction in which it flew.
Next, the teacher goes around to at least two plants or flower heads per plant, and squirts a small amounts of sugar solution into each of several flowers (I’d suggest a minimum of 20 florets per clover head, a minimum of four Stachys flowers per plant). Ask students to predict what, if any, changes in bee foraging behavior will occur with flower enrichment. Ask them why they made these predictions. Finally, test the predictions with a new set of observations. If bee density is sufficiently high, it will be only a matter of minutes before a bee arrives at one of the enriched plants. If bee density is lower, ask the first student who gets a bee at her or his enriched plant to call out, so that all can come watch.
Anyway, students note data as before, and also note any qualitative changes in bee behavior once the bee arrives at the enriched flower.
Discussion: So, why do bees normally leave before visiting all the flowers on a clover head (or Stachys plant)? Which bee would end up getting more nectar, the bee that visited all flowers on every plant or the bee that only “sampled” each plant, staying longer if the sampling yielded bonanzas but leaving quickly if the sampler yielded only blanks? What might be responsible for “blanks”? How would you test this? What might be responsible for the existence of “bonanzas”? Perhaps a plant that hadn’t yet been visited by bees? In which plant would you expect bees to stay for longer: a plant with all bonanzas in its flowers, or a plant with a few bonanzas scattered among many blanks? Why? Can a bee ever get full? What if flowers on a plant produced no nectar whatsoever: what quality of pollination would the plant receive from nectar eating animals? What if flowers on a plant produced great gobs of nectar in each flower, so much that a visitor would “tank up” entirely on the contents of a single flower? What quality of pollination might result?
Finally: do you think that squirting nectar into flowers had any effect on the distance to which pollen was moved by bees? Why do you think so? Can you think of any consequences (to the plant)? And so forth!
Skullcap, Scutellaria integrifolia
37. Antlion Pits
Question: How do antlions dig and maintain their pit?
Season: All year.
Framework: I-3-C-ii (II-5-A)
Needed: Rulers marked off in millimeters or in 1/16”. Small strainers (tea strainers) are nice but not necessary. Graph paper and pencils.
Background Information: Take students to sheltered sandy area where antlions are thick (available in most but not all schoolyards, campuses, and backyards).
First, ask students who knows what an antlion is and what it does (see Handbook entry page 69). In most classrooms a few students, at least, will know. Point out that the antlion digs a slippery sided pit to capture ants. To demonstrate, drop a small ant into what appears to be an active pit (look for one with steep sides and a sharp bottom, with perhaps a little bump—the antlion—at the bottom).
Then, discuss with students: Do they think digging a pit is easy for such a tiny insect? Or does it take a lot of energy? Once the pit is dug, can the ant lion rest easy? Of course not. Digging takes a whole lot of energy, and if the pit is to be effective it must be maintained almost constantly—every ant that falls in, or the wind, or rain, messes up the nice sharp outline.
How To Do It: Next, students search the area for antlions at work. Look for antlions tossing sand out of the bottom of a pit; digging a new pit; circling around the edge of a pit. When a working antlion is found, everyone look. What proportion of antlions are actively maintaining or digging a pit? What proportion are capturing an ant? What proportion are calmly waiting for an ant? How can you tell a pit with an active antlion from a pit that has been abandoned? Finally (and the active part): If digging a pit takes a lot of energy, who do you think can dig the bigger pit, a small antlion or a large antlion? Ask students to make a prediction.
Test the prediction. Measure the diameter of a wide range of “active” pits. For each pit, with a quick movement scoop up the sand at the bottom. Much (not all) of the time you will capture the antlion. Either dump the handful of sand in the strainer, or else let the sand sift through nearly closed fingers. Once the antlion is discovered, measure its length.
Graph ant lion length vs. pit diameter. For young students with no exposure to graphs you can divide pits into three size categories (small, medium, large). Under each category list the sizes of the respective ant lions.
Discussion: Is there any correspondence between ant lion size and pit size? Why do you think this is so? What consequences might this correspondence have in relation to prey size and hunting success? In relation to energy expenditure on pit construction and maintenance? How might you test these predictions?
38. Bottomless Pits?
Question: Can an ant lion be satiated? and related topics.
Season: All year.
Needed: Several active antlion pits, small to medium-sized ants (always available).
Background Information: See #37, above and Handbook page 69.
How To Do It: Students drop ants in at three minute intervals (make sure ants are completely alive and undamaged at drop time), noting whether or not ant lion tries to capture them.
Discussion: How many ants does it take until the ant lion is no longer interested? How fast is digestion in ant lions? How might you test this?
Extension: A related Question: If an ant is dropped into a pit where the ant lion is already having a meal, will the ant lion ignore the new ant and finish its first meal, or will it abandon the current meal for the new one? Does an ant lion consuming the innards of an ant experience a constant intake of energy per unit time, or does the “law of diminishing returns” operate, that is, does the remaining food in the ant become more and more difficult to extract as there is less and less of it? So, which ant lion will get the most energy and nutrients in the long run: an ant lion that always finishes extracting the last calorie from a current ant before it attacks another, or an ant lion that is willing to abandon a half consumed ant if another happens along? Ask students to make a prediction. How would you test this?
39. Spaced Out
Question: Do ant lions try to dig their pits near to, or far from, other pits, and why?
Season: All year.
Framework: I-3-C-ii (I-4-C; I-2-B)
Needed: A large plastic tray (with sides), or a sandbox, or a Coleco wading pool, or some other large container with walls. A sandbox is ideal if it can be requisitioned for 24 hours at least.
How To Do It: Fill container at least 3 inches deep with sand (try to use sand about the same consistency as that in which the ant lions are found). Of course, if you have a sandbox already, the problem’s solved. Next, smooth the surface as much as possible. Next, scoop up at least 10 (preferably more) ant lions from an active natural site (see activity #37 above). Actually, the number of ant lions should be sufficient so that there will be one per 100 square centimeters of the container. For example, in a 1 meter x 50 centimeter container, you would want 50 ant lions (note that you can decrease the size of the sandbox, if necessary, with a wood or plastic barrier). Accumulate the ant lions in a coffee cup or an empty yogurt container until the desired number is reached. Dump them all together into a single spot at the center of the enclosure. Watch what happens—they’ll all dig into the sand at the spot. If any time remains, continue watching as they tunnel through the sand. The big event, though, occurs the next day. What has happened? You can trace the routes of many of the lions by noting the ridges in the sand, diverging out from the central dumping spot. Where did they go? Where did they dig their pits? (Note: you might need to give them another 24 hours, or even more, to dig their pits, as freaked ant lions sometimes need extensive time to recover—but you should definitely look the day after dumping to see the paths they have taken). So, where are the pits? Do ant lions like to dig pits together? Or do they tend to dig pits as far as possible from other pits? Or is there simply a “minimum distance” that is maintained between pits, and outside of this minimum distance it doesn’t matter? How would you test this? Why? What possible consequences to an ant lion could there be if its pit is dug close to other pits? far from other pits? the maximum distance from other pits? If an ant lion is maximizing distances from other pits, do you think that the pits will be “regularly distributed,” i.e., at constant distances from one another? Test this with a ruler. What if ant lions are minimizing distances from other pits: what would the resulting distribution of pits look like? Would there be little clumps of ant lion pits? Why might this occur? If you were to look at ant lions close up, in a uniform patch of habitat, do you think they would seem to be far apart or clumped? answer: far apart. But what if you looked at the same ant lions from a long distance away, say from the top of a tree? Would the ant lions appear to be clumped at that scale? Doesn’t whether things are clumped or regular depend on the scale? Can you think of other examples? (e.g.: pine trees in Florida; houses in a town, viewed from a very low flying airplane versus from a very high flying airplane).
40. Bee Ups and Downs
Question: When a bee lands on a flowering plant, does it move up or down, and why?
Season: Spring (Fall).
Framework: I-3-C-ii (I-3-A-I, II-6-B).
Notes: This works only with plants that have a vertical “spike” inflorescence, in which flowers open sequentially towards the spike’s tip. Best: Florida betony (Stachys floridana) or Lyre-leaved sage (Salvia lyrata) in Spring, dotted horsemint (Monarda punctata) in Fall. Also works fine with Delphinium in a garden. This activity can be done in 45 minutes, honest, but also it could be extended in many directions (e.g., checking nectar amounts in different individual plants of the same species to see how much variation there is; supplementing flowers with sugar water in the opposite direction of the usual; etc.).
Needed: Paper towels from lavatory, ruler marked in millimeters or in 1/16 inches. Flowers in bloom with a spiked inflorescence.
Background Information: If it cannot be assumed that students know that bees are foraging for nectar from flowers, then a brief introductory message is in order.
How To Do It: Then students go out to flowers and observe bees. Each time a bee lands on a new inflorescence, students should note whether it moves up, down, or sideways only before leaving that inflorescence for another. After 15 minutes or more, students compare notes and the teacher tallies the number of instances of each kind of movement.
Discussion: Now, which is the most frequent movement direction, up or down? Assuming that one is more frequent than the other, why? Students have any explanation? Ask them to devise easy experiments to test their hypotheses. After this free for all, ask students if they noticed where the older and younger flowers were located. Then ask them if that modifies their explanation. What if younger [or older] flowers produce more nectar? Or what if all flowers produce some nectar before or just after opening: which flowers would most likely have had that nectar removed, old ones or young ones? So, where would an incoming bee most likely find the greatest quantity of nectar? On the other hand, what if all flowers produce some nectar throughout their lives, so that old flowers have accumulated more than young flowers?
More To Do: How can we figure out what’s going on? Try to figure out the bee’s perception of nectar available at the time it visits the plant. How can you do this? Simple. From an inflorescence, carefully pluck off the flowers one at a time. With each flower, carefully break corolla off from ovary. Carefully squeeze any nectar inside onto the filter paper. Measure the diameter of the wet circle that results.
Further Discussion: Which flowers tend to have the most nectar, upper ones or lower ones? Does the bee start with the flowers that should have the most nectar? Why? What would it signify, to the bee, if the flowers expected to have a lot of nectar actually didn’t have any? What might the bee “decide” then, in terms of continuing to check all flowers on the plant versus leaving immediately? What would it signify, to the bee, if the flowers expected to have a lot of nectar indeed had great gobs of it? What might the bee “decide” then, in terms of continuing to forage at flowers on that same plant? In other words, when “should” the bee leave the plant and move to another, in order to accumulate the most nectar during its foraging bout, and how is that decision modified if the bee discovers (a) a lot of nectar or (b) only a little nectar in those locations where flowers should have the most? Etc. etc.
41. Spider Directions
Question: Are spiderwebs oriented in a particular pattern, and why might this be so?
Season: Fall (Spring).
Framework: I-3-C-ii (I-2-A, II-5-A).
Notes: This activity is #14 re-written to emphasize a different topic on the framework outline. Otherwise it’s no different—I just managed to make it more complicated.
I’ve written this as if students knew about (a) compass directions and even about (b) angles from the vertical. For younger students, this activity might be a great technique for teaching students about either (a) or (b), thus providing a nice geography and/or geometry exercise as well.
Needed: A fair number (at least 15 20) spiderwebs of a single kind, in hedge, on forest edge, in weeds, on shrubs, or wherever; a cheap compass or two; and, for optional part, protractor to whose origin is attached a piece of string about 20 centimeters long with a pebble or fishing weight taped to the end (i.e., a plumb line).
How To Do It: Main part: Students determine compass direction of each web. Chart these on a circular chart marked with compass directions.
Discussion: Do the webs appear to be going in all directions, or is there a consistent compass direction? Now, why might this be so? Might it be because prevailing winds come from a certain direction, and if so, what does this have to do with it? Might it be because that particular direction, in the hedge or whatever, is the direction that exposes the webs the most to the open air, and if so, what does this have to do with it? What is the orientation of the webs with respect to the orientation of the sun’s rays, and what might this have to do with it (could the sun reflect off a web oriented perpendicularly to it, thus warning off insects?)? What direction does the sun move, anyway? Let students come up with their own explanations, and for ways in which these might be tested.
Extension: Optional part: Measure not only orientation but also verticality of webs. Again, chart on a circular chart. Do webs appear to be at all angles, or a fairly consistent one? Vertical, or slightly tilted? Explanations? What about other spider species? In the same habitat, and on the open areas, as well, should be extremely common sheet web weavers of various species, which weave a horizontal web. Why might different spiders have their webs at different angles from the vertical? Ask students to come up with reasons and tests. Hint: The size and flying ability of insects might have something to do with it.
42. Fishing Without a Net: Webless Spiders
Question: How do wolf, crab, and jumping spiders hunt, and just how successful are they?
Season: Fall (Spring).
Framework: I-3-C-ii (II-5-A, II-5-B).
Needed: Clip boards, pencil and paper.
Background Information: See Handbook pages 55-58.
How To Do It: Students hunt litter, flowers, and vegetation, respectively, for these three kinds of spiders, and upon encountering a spider, they observe it for 2 to 3 minutes before moving on. They note whether or not spider is eating something (somewhat unlikely except for crab spiders), or whether it captures something in the observation interval (highly unlikely). Observe spider behavior.
Discussion: Which one sits still and waits for its prey to come to it? What special features of this spider enhance its ability to wait undetected by potential prey, and to capture the prey quickly once they come near? What’s the difference in movement patterns between jumping spiders and wolf spiders? Which one do you think leaps on its prey, and which one runs its prey down? Which one do you think has better eyesight? How can you tell? Does any one of these spiders also spin silk? So, why don’t they build webs? What do they use the silk for? How can you tell (let a jumping spider crawl on you)?
In general, what are the similarities and differences among these spiders in the ways in which they capture prey? Are they equally successful, or is one mode apparently more successful than others? Do they seem to be as successful as web building spiders? What’s the trade off? Do web building spiders invest more or less time and/or energy in a prey capture mechanism than do the three webless modes? So, might the prey return and energy invested be about even? Etc. etc. etc. The main idea is to get students to watch spiders and realize that they’re quite different from one another.
43. Too Close for Comfort
Question: Do plants growing in clumps experience more leaf munching than isolated plants?
Needed: Meter sticks (Okay, yardsticks in stubbornly un metric enclaves) or some such measuring equipment, clip boards, pencils and paper.
Any lawn weed (see Handbook pages 42-43), lawn edge weed, or vine (e.g., sweetbriar (Smilax), grapes (Vitis) or Virginia Creeper (Parthenocissus) that is quite abundant, varies in density (i.e., there are some scattered individuals and some dense aggregations of individuals), and experiences some easily visible herbivory (holes munched in leaves). There should be many candidates, depending on the school. Teacher must select the plant prior to the exercise, but this should take all of 5 minutes to do.
Season: All year (this is slightly more difficult in winter or early Spring).
Framework: I-4-C (II-5-E)
Background Information: Very short discussion about how many kinds of insects (e.g., butterfly and moth caterpillars, beetles) munch on plant leaves. Some move from plant to plant.
How To Do It: Ask students to predict: what plant will most likely get munched more, one that is close to others of the same kind, or one that is sitting off alone?
How to estimate herbivory? Many ways; choose the most suitable. Easiest: percent of leaves that have visible herbivory (e.g., > 10% removed); or, average % herbivory from three “randomly chosen” leaves per plant (students can estimate the amount of leaf area removed, to the nearest percent, - or, if percent, to hard numbers, one for clumped plants, one for isolated plants).
Discussion: Which column has the bigger numbers? No, you don’t have to do statistics. Discuss the results. Do they suggest that isolated plants do better? Suffer less herbivory? Is herbivory bad? What does herbivory mean to the plant? Might the plant be able to grow less tall? Produce fewer flowers or seeds? If so, how could plants become isolated from one another? Do they have any choice? Can a plant move from a clump to an isolated spot? What are some other benefits of isolation (hint: lower competition for necessary nutrients, etc.)? What are some costs of isolation? What about pollination? Seed dispersal? Speaking of seed dispersal, if students have found out that isolated plants experience less herbivory, then might this be an advantage to a “mama plant” having its seeds scattered, by wind, water, or animals, rather than having all the seeds fall right together at its feet? Discuss agricultural implications. What do people do: plant isolated plants, or plant huge clumps? Follow this reasoning to its conclusion: pesticides etc.