Mealworms

Reprinted from The Wild Times Teacher Connection v2n3, Spring 1997.

One of the most successful and simplest activities that I have done with first graders is to raise mealworms. We have done this for several years as part of our study of insects. Mealworms are the larvae of the darkling beetle (genus Tenebrio). They are not really worms at all. Most pet stores sell them to feed various small animals, so they are readily available and inexpensive.

Culture

Mealworms happily subsist on a diet of bran or other cereal products with occasional treats of apple, other fruit or vegetable matter, or even a chicken bone. They do not escape from an open container. Even as adults, the beetles do not fly. In our classroom, we keep a large colony in an open, straight sided glass container. The container is about half full of wheat bran to which I add more every few months. The insects live right in their food. About once a week, I cut up an apple and add it to the habitat. About once a year, I clean out the container, sort the inhabitants from the litter and put in completely new bran. That is all there is to maintaining the habitat. My colony has been going for nearly twenty years.

Activity

The following is the activity as I have done with first graders. It could be done with most any age group, but with more sophisticated observations and recording of data with older students.

Materials:

1 larva per student, wheat bran, plastic cups, occasional apples.

Each student has one larva ("worm") and a cup with bran in it. The children are responsible for caring for it to adulthood and beyond. They feed them slivers of apple and watch the development. It takes as long as six months for the adult to develop, so this is an ongoing activity that continues for a good portion of the school year. Meanwhile, the students see the insect larvae grow, shed their exoskeletons several times, and pupate.

The larval stage may last several months, where as the pupal stage lasts for several weeks. Patience is important. Finally, one day a nice black beetle about 15-18 mm (3/4 of an inch) long hatches out. At this point, I allow the students to take them home if they would like. Some would rather keep them at school because they are not sure of the reception they will get at home, and that is fine too. Writing to the parents about the project explaining the care and feeding of the darkling beetles, and reassuring them that this one beetle is not going to become an infestation in their house is advisable. We had one boy whose beetle lived in its cup of bran at home for about eight months. His whole family got involved in the care of this amazingly long-lived beetle. We got frequent updates at school about how it was doing.

Observations:

Observations can be structured around specific topics and associated questions such as the following:

1. Life cycle

What stages did it pass through? Do all the beetles pass through the same stages? Do they all take the same length of time to do it? What stage did we not see? (eggs - they are too small to see in our habitat).

2. Behavior

Where do the mealworms like to stay? What happens when you put one on top of the bran? What happens when you put a sliver of apple in the cup? Do the pupae move? Do the beetles behave like the mealworms in any way? Do the beetles and the larvae like the same food? What treats do they seem to like best?

Recording Data

Since first graders may still be struggling with trying to record their ideas in writing, group writing with the teacher recording the ideas may be the best way to write about this activity. Having the students speak into a tape recorder is another way. The students can also record the stages of development in drawings. Keeping a chart of length of time of development is also a good idea.

From my experience with this activity, one of the things that seems to make it a success is the personal interest that the students take in their own individual "pet" beetles. They name them and boast to each other about their charms. They check them carefully whenever they are in the science room. If one should die, there is distress. We always have plenty in our parent colony to replace any that die prematurely. But death is part of the life cycle too, and therefore, part of the lesson.

Lucy is a member of The Wild Ones Advisory Council, and teaches science at the Chestnut Hill Academy in Philadelphia, PA USA.

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