Introduction: Hornworm to Hawkmoth: Metamorphosis (Grades K - 4)
Starting in Kindergarten, children usually have a good understanding of the change from caterpillar to butterfly from books and learning at school. However, getting an opportunity to watch that process happen makes the science and wonder of metamorphosis so much more exciting! I especially like using hornworms because they are easy to obtain and handle, and not as familiar as some of the caterpillars that kids are used to. I've included a printable that I use for my Kindergarten, Grade 1 and Grade 2 students that encourages them to draw and label what they observe, and then make a hypothesis about what the hawkmoth will look like. The awesome thing about hornworms and hawkmoths is that they look nothing alike, which makes the predictions very interesting, and leads to further discussions about why they look so different (adaptations, survival in different forms, mating, etc).
I've added 4 booklets above for use with this unit.
I am an Elementary Teacher in Ontario, Canada and have taught everything from Kindergarten to Grade 8, ESL, Spec Ed and Library in the past few years. I am a proud science nerd and share that passion with all my students. I've used this unit for many different grades and groups, and we have all enjoyed every iteration of it.
Glass bowl or vase
About 6 Hornworms (available at most reptile pet stores)
5 or 6 sticks about 25 cm long (I collect them outside of my school)
Terrarium OR aquarium OR with a screen top
Spray bottle of water
Small bowl of sugar water
Paper for Booklets
Step 1: STEP 1: CHOOSE AND PRINT BOOKLETS
I use these booklets for students to document their learning and begin to understand scientific ways of documenting learning. I've included two Grade levels (Kindy/Grade 1 and Grade 1/2) and two spelling versions (CDN - Canadian and US spelling). Please pick the one that best suits your students reading/writing levels and geographic location.
All booklets should be printed double sided, and each group of pages produces two booklets. Note that the cover page on the Kindy/Grade 1 is printed last due to it having an uneven number of pages.
Step 2: STEP 2: SET UP THE OBSERVATION STATION
Gather the supplies you will need for the first part of the process. I like to use about 6 hornworms that I get at most pet stores that sell reptiles, as they are used as food for reptiles like my bearded dragons. Ask the staff to help you pick hornworms that are older and bigger. The best ones to get have a dark pulsating line down their back. This is their aorta and it only pulsates visibly when they are ready to build a chrysalis. Choosing older hornworms shortens the time that curious students need to wait to see them build their chrysalis.
Place the hornworms in a container such as a glass vase or low bowl with potting soil to about 2/3 full. Do not overfill as the hornworms are great climbers and might escape. I prefer glass so that kids can see the hornworms as they tunnel in their wandering phase (more about that in a bit), but it needs to have an inverting lip at the top to keep them in (see picture above - Rory the Shepherd's nose for scale, and because she wanted to "help").
I use aquariums or terrariums to place the bowl in to protect the hornworms from inquisitive fingers, but you'll also need something for the hawkmoths to dry out and fly in, and so the aquarium/terrarium serves that purpose as well. You could also use a butterfly net for the same purpose (and example can be found here). I take the bowl out during instructional time to view the hornworms, but leave them protected otherwise as they need to be physically undisturbed in order to build their chrysalis.
Have the students complete the hornworm observation page in their booklet. Remind them to draw the hornworms using the correct size/measurements, colour, and body parts like good scientists do.
Hornworms go through a "wandering phase" right before building their chrysalis, which involves tunneling through the soil and literally wandering all over the place. If you notice them engaging in this behaviour right away, it is not necessary to feed them as they will not eat when they are ready to change. However, if they are not tunneling and you can't see the pulsating aorta on their backs, you will need to feed them potatoes and carrots until they start wandering.
NOTE: DO NOT GIVE THEM WATER OR ADD WATER TO THE SOIL unless it is extremely dry. They breathe through their skin and do not tolerate water well. The soil should be clumpy but not soggy. I use a spray bottle if it dries out during the process, but mist lightly.
Step 3: STEP 3: WATCH MAGIC, I MEAN SCIENCE, HAPPEN
After a few days of wandering, the hornworms will suddenly place themselves head up in the soil and stop moving. If you have a way to set up a camera using video or stop-motion, do it now! The process of building the chrysalis takes about 36 hours, but it is wonderful to see. The hornworms start by stripping their outer layer of skin and legs, and then slowly build the outer layer of the chrysalis, changing in colour from teal to brown.
Have the students complete the chrysalis observation page. Again, remind them to think about size/measurements, colour, and the structures that they see.
The hornworm will stay in chrysalis for a long time - at least a few weeks. Keep the soil from drying out but otherwise leave them alone. However, you may want to take them out just once to show the kids how they WIGGLE in the chrysalis! This is also an important time to put the bowl in an aquarium/terrarium/butterfly cage and GENTLY place sticks into the soil without touching the chrysalises so that they have something to climb to dry out their wings once they leave the chrysalis. Make sure you put a screen over the aquarium/terrarium so they can't fly out.
Once students have had a chance to see the chrysalis change for a few days, have them complete the hawkmoth PREDICTION page. What do they think the hawkmoth will look like based on their observations of the hornworm and chrysalis? What size, colour and body shape will it have?
Step 4: STEP 4: HAWKMOTHS!
If everything went well, you will have hawkmoths erupting from the chrysalises. The red fluid you will see is a lubricant that they produce during the massive changes happening in their bodies, and is perfectly normal. You will want to put some sugar water in a bowl in whatever container you are using for them to help strengthen them for flight. Watching them drink with their long, curled tongues is fascinating!
Have the students complete the hawkmoth observation page, and for the Grade 1/2 booklet, complete the surprises they might have had in the change they observed. Remind them to use as much detail as possible.
Hawkmoths only live for about 2 weeks, and can be released in most of the US and Southern Canada, as they are naturally found in those areas.
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