Skip to main content


Mystery Critters

Naturalistic studies provide opportunities for students to develop observational skills

The process of science requires students to understand the natural world through personal experiences (Clough 2006; McComas 1998); however, the experiences many children have in their science classes consist of the memorization of facts or vocabulary (Pasley et al. 2004), a boring and often tedious task. According to the National Survey of Science and Mathematics Education (2018), only 16% of the elementary teachers surveyed reported including hands-on activities in all or most of their lessons. Strategies that engage students in hands-on investigations help improve student achievement (Minner, Levy, and Century 2010) and provide students with a joyous opportunity to explore natural phenomena firsthand. Another aspect of science that elicits joy from students is the opportunity to document their observations and share what they’ve learned with others. Creating opportunities for students to actively engage in authentic scientific processes in multiple ways helps alleviate student misconceptions about the nature of science. To this end, we developed a lesson plan that supports a class of third-grade students in their understanding of organism growth and life cycles by providing them with a “mystery critter” to observe. This lesson was designed to integrate the use of science journaling and inquiry to help students improve their observation skills and create testable questions to gather more information on their critter’s needs, behavior, and growth.

This unit is in keeping with the recommendations from the NSTA Position Statement for Elementary School Science (2018) that teachers should allow students to design their own investigations, practice science with a group, and allow for science discourse to share their findings and make evidence-based claims. To accomplish these goals, the Next Generation Science Standards (NGSS) standard 3-LS1-1 From Molecules to Organisms: Structures and Processes was used for this lesson. Students were asked to develop models of unique organisms to understand the stages of life and growth. The disciplinary core idea of growth and development was additionally reinforced during this lesson.

To guide students in developing an understanding of an organism’s basic needs and life cycle, we designed an inquiry-based unit focused on mealworm beetles (Tenebrio molitor), which are a species of darkling beetles. Activities took place over a three-week period that allowed students plenty of time to make observations and create life cycle models of their critters. Students worked in groups to observe their critters, devise simple tests, and share their findings with others. Toward the end of the lesson, additional organisms were brought in to help students use firsthand observations to discover the similarities and differences between the organism’s life cycles.

Teacher Preparations

Science labs that include both journaling and inquiry require advanced preparation prior to student exploration. This investigation incorporates the use of a scientific journal for documentation of observations, asking questions, and gathering data. If you have not used a journal in the past, this activity will allow for an easy transition and a great starting point to promote scientific writing and communication. We have shared journal templates online (see Supplemental Resources).

Plan to obtain mealworms from a local pet food store at least a month in advance. The larva stage of a darkling beetle can last up to nine weeks; however, this lesson is designed to conclude in three weeks. Due to this time constraint, we recommend separating the mealworms into two groups to force the maturation of the larva. The first group should be placed in an open container with an oatmeal substrate and slices of potato for nutrition. These mealworms will mature into beetles faster than the second group, allowing students to observe multiple stages of the darkling beetle’s life cycle. The second group should be stored in a refrigerator to keep the mealworms in a dormant larva stage.

You will need a variety of containers, substrates (oatmeal, grits, rice, Malt-o-Meal), heat lamps, and food sources (apples or potatoes) for students to develop unique tests between groups. Obtaining these materials beforehand will make for a smoother transition in the coming weeks. Before passing out student containers of the critters, add an oatmeal substrate to several containers along with four to five mealworms at as many different life cycle stages as possible: mealworm (larva), pupa, and adult beetles. This allows students to observe characteristics and behaviors for all stages of growth in the shortened time of our observation.

Tip: Mealworm eggs may be difficult to observe for students due to their size and hidden location. A tip to locate eggs is to use a brightly colored plastic container during your prep time. Before you separate the critters for students, sift out the adult beetles and bedding using a 1/8 in. sieve. You may notice some white spots left behind on the plastic container. Generally, these are egg clusters, but you may find some in the substrate with careful observation.

This activity can take anywhere from two to three weeks or longer depending on your scope and sequence and the stage of your mealworms. This timeline depends on the components that the teachers want to include, the span of standards that will be covered, and the grade level of the students.

Safety Considerations

To ensure the safety of the mealworms and students:

  • Obtain the mealworms from a commercial vendor.
  • Provide adequate living quarters, bedding, food, and water. Remind students to treat all animals with care. No experimental procedure should cause pain or discomfort to the animal.
  • Wash hands and surfaces before and after handling the mealworms. Non-latex gloves could be used. Remind students not to touch their eyes, mouth, or face.
  • Check for food allergies among students when selecting food sources for mealworms.
  • At the end of the investigation, do not release the mealworms into the wild since they are a nonnative species. Consider using them as a food source for reptiles or other classroom pets.


Our investigation began when students were presented with a container of “mystery critters” (mealworms). Over the next two weeks, students observed their critters and recorded their observations in their science journals. Depending on student ability, students either completed their journal entries individually, in small groups, or during class discussions. When the students first received their critter, they had time to make initial observations and become acquainted. For some students, their initial reaction was that their critters looked gross. As student observations progressed, they become fascinated with our guests and used basic observation tools such as scales, magnifying glasses, and rulers to collect data. As each student noticed something new about the changes their critter experienced, it fed their sense of ownership of discovery—something to enjoy sharing with their peers. This gave students time to talk with classmates, point out interesting features, and pique their curiosity about their critters and upcoming activities. During student observations, we moved around the classroom and asked a series of probing questions: “Are all of your critters the same?” “Can you describe what your critters look like?” “How do they move?” and “What happens when you gently touch your critters?” The opportunity to observe their mealworms through touch and experience the tactile feedback of the mealworm’s corresponding movement isn’t something that can be replicated through observing images in a book. After students made some basic observations, we held a class discussion to see what they noticed about their critters and what questions they wanted to be answered (Table 1). The class chart was included in the student’s science journal for future reference.

Table 1.

Class list of what we know and what we want to know.

What do we know so far?

  • There are some pieces of skin
  • I have three different critters in my bowl
  • One critter looks like a worm with legs
  • My worm critter is _______cm long
  • I have one that isn’t moving, I think its dead (pupa)
  • I have a black bug that moves quickly when poked
  • My worms like to hide under the oatmeal
  • My black bugs can’t climb the wall My worms are brown

What do we want to know?

  • What do they eat?
  • Do they drink water?
  • Do they sleep?
  • How old are they?
  • Why are they in oatmeal?
  • Will they grow?
  • How many critters do I have?
  • Why are they hiding under the oatmeal?

After the initial meeting, students began to document the contents of their container. This included a picture of what the container looked like and what types of critters they had. They did not need to use scientific names at this point but were asked to draw a basic sketch of their critters and the number of each variety. Note: Depending on the time between the Engage and Explore activity, you may want to consider adding a slice of potato to the containers for nutrition until your next science class.


During the Engage activity, students had the opportunity to gather some initial information about their critters and develop testable questions or what they wanted to know. Students had an easy time developing testable questions due to their curiosity and their desire to learn more. Not all of their questions were appropriate for investigations, for example, “What happens if we leave our critter in the Sun all day?” or “Will our class snake eat our critters?” Though students were clearly excited, they did need to be reminded that we didn’t want harm to come to our critters. After students had time to brainstorm, we worked as a class to develop a list of variables that may be important during their observations. Table 2 shows a table of class variables and why students may want to test them during an investigation.

Table 2

Class list of important variables to test.

List of variables that might affect critter growth and development

This Variable Might Be Important

Reason for Inclusion

Type of bedding

They may use their bedding for food.

Temperature of container

Some animals can not survive in really cold or hot weather.

Time of observation

Some animals are more active during the day or night.

Type of food you provide

Some animals only eat meat or plants.

Type of water source you provide

Some animals get their water from the foods they eat.

Each group of three or four students was expected to test one question from our list of variables during the Explore stage. For example, one group chose to test the different types of bedding and divided their critters into containers with oatmeal, grits, and Malt-O-Meal. Students then set up their critter diary for future observations with an explanation of the basic test design. They used a prepared handout (see Supplemental Resources) with guiding questions that helped them record their observations and make inferences about what they saw. Students observed their critters and noted any new observations or changes three times a week (more if there was time). Students would often come to class early, after lunch, or when they had downtime to check on their critters.

Students took part in the exploration portion of the lesson for 10 days. This provided enough time for students to begin to observe some changes in their critters’ appearance. Some common statements from student journals included, “critters stay underneath bedding,” “I found some pieces that look like dead skin,” “my critters hide under the potatoes,” and so on. As the students made their observations, we rotated throughout the room to answer any questions. To encourage further inquiry, we used several higher-order questions that were tailored to each group’s investigation. Examples include:

  • Describe what happens when you added _______ to your critter’s habitat.
  • How would you develop an experiment to test _______ [food preference, light aversion, bedding preference, etc.]
  • What does your critter’s behavior of hiding under its bedding suggest?
  • What explanation do you have for why your critter ________?
  • What evidence supports your idea that your critter _________?


After two weeks of critter observations, we introduced the concept of life cycles by asking students “Do humans look the same as we get older?” Most students responded that we kind of looked the same, but that older people were taller, heavier, more wrinkled, or had grey hair. We followed up this question by asking if plants or animals changed forms as they developed. Students provided examples of baby animal characteristics compared to their parents. This provided us with a segue into the stages of life cycles and what they had observed during their critter observations.

To expand the student’s knowledge about mealworm habitats, basic needs, life cycles, and life span, we integrated a research component into the lesson. Mealworms, a nonfiction text by Donna Schaffer (2003), was provided to students to fill in any information gaps and help students complete a model of a mealworm life cycle with labels. When students read the book, they were instructed to compare their journal entries with the facts listed and search for any incorrect or missing information. Students at this point were beginning to put scientific names to the observations they had made over the past few weeks and were sharing their findings with other groups to practice communication with a wider audience.

Once the students completed their research, the class came together to discuss their findings. At this point the class developed a model of the mealworm’s life cycle, named the stages, and provided any important information about its growth and basic needs. To help students make a connection between the explore and explain stages of the lesson, the following questions were used:

  • How would you recognize your critter has gone through a new stage of its life cycle?
  • How would you differentiate between the larva stage and the adult stage of your critter?
  • How would you demonstrate that your critters always go through the same stages of life?
  • How can you compare the different stages of your critter’s life cycle?
  • How are your critter’s stages of life connected to its habitat and needs?

Students were also asked to share findings from their investigation, such as the substrate did not seem to matter, they preferred potatoes, and mealworms didn’t like light or heat. During the discussion we asked students to provide evidence from their journal that reinforced their findings. This could have been written observations, diagrams, or data collected.


During the next few days students researched a variety of different organisms and their life cycles from school library books. Each group was asked to research a different organism from a predetermined list that included a variety of different plants and animals. The list included butterflies, ladybugs, frogs, chickens, apple trees, and tomato plants. Students did want to add organisms to the list provided by the teachers, so to maintain student engagement, these additional organisms were added to a “parking lot” poster and could be revisited if there was additional time. During their research students needed to draw each stage of the organism’s life cycle, determine the length of each stage, and gather interesting facts. The student research sheet is included online (see Supplemental Resources).

In the next activity, we asked students to create a presentation for the class to show a comparison of their new organism to the mealworm (critter). Presentation formats could consist of posters or a digital option using Google Slides or another poster-making application. To help modify for struggling students, we created a template in Google Slides. This way students could focus more on enjoying the opportunity to share their discoveries rather than the design. A rubric (see Supplemental Resources) was provided to students to help them organize their collected information and self-evaluate their presentations during the creation process. Students presented their products to the class and discussed the similarities and differences between their two organisms. During this activity, we encouraged the use of scientific vocabulary and asked the students if our original questions from our mealworm investigation could apply to our new organism.


Throughout the unit we provided multiple activities that were used as evaluations. We assessed student’ science journals, used probing questions during investigations, and had students complete a short comparison activity to other organisms. The presentation provided a culminating evaluative experience and gave students an opportunity to compare and contrast mealworms with different organisms. Students were encouraged to look for similarities and differences between each organism, but ultimately found that although the stages may look a little different between organisms, they all have a cycle of life and growth. Final reflection questions for the unit included “What was something you learned about your organism’s life cycle?” “What else would you like to know about your organism’s life cycle?” and “What did you notice about each of the life cycles that happened repeatedly?”


Providing students with the opportunity to personally experience the life cycle of an organism through direct observation and investigation gave our students the opportunity to enjoy stretching their scientific wings. Students were able to learn through inquiry by creating models of their organism’s life cycle and reevaluating them as new information came available. Documenting observations in their journals provided us with an opportunity to assess their progress and help them develop literacy strategies and communication methods as they got to enjoy the opportunity to play an active part in the class’s ability to collect and organize their observations about the mystery critters. In the end, the third-graders were able to compare their personal experiences with their mealworms to other organisms through research, developing stronger content knowledge about life cycle stages and the basic needs of organisms.


Thank you to Dr. Sissy Wong at the University of Houston for engaging her students in naturalistic inquiry and providing the idea of how to use “critters” in the classroom.

Supplemental Resources

Download the journal entry sheet, research sheet, and rubric at

Allison Esparza ( is a doctoral student in the Teaching, Learning, and Culture Department at Texas A&M University in College Station, Texas. Sara Raven is a UX Research Lead at JP Morgan Chase and Company in Atlanta, Georgia. Kaelyn Parks is a doctoral student at Texas A&M University.


Clough, M. 2006. Learners’ responses to the demands of conceptual change: Considerations for effective nature of science instruction. Science & Education 15 (5): 463–494.

McComas, W.F. 1998. The Principle Elements of the Nature of Science: Dispelling the Myths. In The Nature of Science in Science Education: Rationales and Strategies, ed. W.F. McComas, 53–70. Netherlands: Springer.

Minner, D.D., A.J. Levy, and J. Century. 2010. Inquiry-based science instruction—what is it and does it matter? Results from a research synthesis years 1984 to 2002. Journal of Research in Science Teaching 47 (4): 474–496.

National Science Teaching Association (NSTA). 2018. NSTA position statement: Elementary science education.

Pasley, J.D., I.R. Weiss, E.S. Shimkus, and P.S. Smith. 2004. Looking inside the classroom: Science teaching in the United States. Science Educator 13 (1): 1–12.

Schaffer, D. 2003. Mealworms (Life cycles). Mankato, Minnesota: Capstone Press.

Biology Life Science Teaching Strategies Elementary

Asset 2