Investigating Macros in the Classroom

By Isabelle Spohn, Brewster School District

I  have the students identify macroinvertebratess in jars and an aquarium.  I collect them close to home where the water is more abundant and healthier. 

After gathering the insects in jars on a Sunday, I keep them in my refrigerator overnight.  This works very well, and they are very lively in the morning. I  attempt to put as much variety of insect types in each jar as possible, using a turkey baster to re-distribute them - one jar to each group of 4 or so.   One year I had an especially capable class and allowed them to use the turkey basters themselves to catch the insects in the little bug boxes with magnifiers and also place them under the microscopes in the bug boxes to observe. I emphasize looking at the mayfly gills work.  The trick is not to leave any insect under the microscope too long, since the light heats the water up so quickly.

Stream insects:

It has been most successful if I can keep the insects from the stream separate from those from the wetland.  The oxygen demand of the stoneflies and some of the mayflies from the streams is great and it is difficult to keep them alive - especially the larger varieties of stoneflies, which sometimes have many gills, sometimes in large clusters. So if I keep them separate, I am able to return those from the stream sooner than those from the wetland. I attempt to return them to the place where I found them the day the students see them if at all possible, unless they are showing signs of stress. In that case I get to a spot in the river that has a riffle and put them there as soon as I can get there.

I like to keep the insects in jars at first for the students to observe and try to have at least one jar per table of 4 students - before putting them into the aquarium.  This year I was able to have several jars with only stream insects also.  I had rocks in them, and the stream insects naturally  clung to the bottom of the rocks - however, they could be seen through the bottom of the jar.

Keeping the water cold is the hardest part.  I generally get a bag of ice and keep putting it into the jars or aquarium to cool the water down.  However, I suspect it is chlorinated and it may be better to use ice cubes from home. One year I had a refrigerator in my room, and this really helped.

This year, I had some large stoneflies who were getting stressed out even during the morning, so I had to place them in the aquarium with more water and an oxygen pump early in the day. Even then, at least one of them died before I got it back to the river that afternoon.

I try to include some rocks and some leaves, for both the shredders and the scrapers.

This year, I added flashlights to the equipment, which definitely made it easier for the students to see them, especially since with this year's group I am not comfortable letting them use the turkey basters.

I keep turkey basters handy, because if I have an insect that is stressed out in a jar (this has happened with some of the larger stoneflies) I can put air into the jar with the turkey baster and it seems to relieve the situation. 

Wetland insects:
 
The wetland insects are a little easier. I try to include rotten vegetation for them to eat, sticks and longer grasses for the caddisflies to cling to, etc., so the kids can see them moving around. After the first day, when the students have identified the insects in jars, I put them into two small aquariums (the $10-15 WalMart variety.) They are the type with a light, which definitely helps in seeing the insects. A flashlight could help too.  Then the students can watch them at their leisure in a more natural habitat. It is amazing to see how quickly the decaying vegetation collapses and disappears.  The students can see how each insect moves or swims -  the damselflies are especially graceful - and I have even observed some of the carnivores attacking each other, once under the microscope. With some of them, you can also watch the gills work even without a microscope (especially the mayflies.)

I only keep  the wetland insects  3-4 days at the very most. Most times it is a couple of days.  If any insects emerge during that time, the kids can see the exoskeleton floating on top and can see what the adult looks like.  We catch them and put them outside. As you can imagine, some students just park in front of the aquarium and could watch forever - as could I.

The next time I do this, I intend to put two pumps in each aquarium to keep the oxygen flowing better. .  I am still looking for a better way to cool the water down than with ice cubes. And if the light is on, it of course warms the water even more.   It would be excellent if I had a refrigerator large enough to hold the aquarium.  I think that even without the air pump, the insects would do well in the cold water overnight.   My observation is that the water warming up is the most challenging condition for the bugs.

I also show some videos from the ESD on water insects during this time and have a lot of identification sheets.

When the kids then go to the stream, they are able to identify the insects readily and have some idea of what they do under the water as well as a comparison with the wetland insects.

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Updated Spring, 2005