Most people see a caterpillar and think about nature.
Engineers see a system.
💡This way of thinking is central to what we call the Builder Development Framework, in which learners develop their understanding by interacting with real systems rather than simply receiving information.
Related Reading: The Builder Development Framework
A system with constraints, resource requirements, structural transformations, environmental variables, and remarkable resilience.
This spring, my family and I embarked on a simple citizen science project in our garden: raising Black Swallowtail butterflies (Papilio polyxenes). What began as an opportunity to observe nature quickly became something much more—a living demonstration of the same design principles that drive engineering, scientific discovery, and deep learning.
More importantly, it became a reminder that some of the most powerful learning experiences don’t begin with a lesson plan.
They begin with curiosity.
Building a Backyard Laboratory
Every successful engineering project starts with understanding the system you’re working with.
For Black Swallowtails, that system begins with a specific set of host plants. Unlike generalist insects, these caterpillars rely almost exclusively on members of the carrot family, including fennel, parsley, and dill.
Our garden already contained several mature fennel plants, making it an ideal environment for observation.
To create a safe and observable learning environment, we assembled what we called a “Builder’s Laboratory”:
- A ventilated enclosure with excellent visibility
- Fresh fennel stems maintained in a protected water source
- A simple observation area lined with paper towels for easy cleaning and daily monitoring
- Natural branches and supports for eventual pupation
The setup required very little equipment, but it created something far more valuable than a science project.
It created a reason to pay attention.
Every day brought new questions:
- Why are they eating so much today?
- Why do they suddenly look different?
- Where are they going?
- What happens next?
These questions became the curriculum.
Stability: The “Girdle” and Anchor Engineering
- The Anchor Point: Caterpillars naturally seek a vertical or angled substrate to pupate; provide sturdy, rough-textured twigs (1/4 inch diameter) as primary structural supports.
- The Silk Girdle Technique: In the wild, the larva spins a silk “button” and a safety “girdle” to hold its weight during the transition; you can assist this by ensuring the enclosure has ample vertical surface area (e.g., mesh walls or wooden dowels) to prevent the larva from attempting to pupate on the container floor, which can lead to deformity.
- Structural Integrity: Avoid moving or shaking the enclosure once the larva begins its “wandering” phase (the pre-pupation state), as the attachment of the silk girdle is a delicate, one-time mechanical bond that is easily broken.
The Experiment: Two Paths, One Goal
As the caterpillars grew, we decided to conduct a simple comparison.
Instead of bringing every caterpillar indoors, we divided our observations into two groups.
Track A: The Laboratory Group
Three newly hatched caterpillars were moved into the enclosure.
Inside, they experienced:
- Consistent access to fresh food
- Protection from predators
- Stable environmental conditions
- Daily observation and care
Track B: The Wild Group
Three caterpillars remained in the garden.
They faced:
- Changing weather conditions
- Wind and temperature fluctuations
- Natural predators
- Competition and environmental uncertainty
Both groups began with the same biological blueprint.
What differed was the environment.
For children, this created a powerful lesson: systems can follow different paths while still arriving at successful outcomes.
Six Newly Hatched Caterpillars
│
┌─────────────┴─────────────┐
▼ ▼
Laboratory Group Wild Garden Group
Controlled Inputs Natural Variables
Protected Growth Environmental Challenges
│ │
└─────────────┬─────────────┘
▼
Successful Emergence
The laboratory group allowed us to observe every detail of development.
The wild group reminded us just how resilient nature can be.
Together, they provided a real-world lesson in adaptation, systems thinking, and environmental design.
💡The same principles of experimentation and iteration appear in many of our favorite maker projects.
Explore: Bug Machines: Where Play Evolves into Engineering
Nutritional Inputs: Managing Larval Consumption
- Host Plant Selection: Fennel (Foeniculum vulgare), parsley, and dill are preferred because they contain the specific furanocoumarins and volatile compounds required by Papilio polyxenes larvae.
- The “Freshness” Variable: Caterpillars are highly sensitive to plant turgor pressure; wilted or dried-out foliage leads to decreased consumption and sub-optimal growth rates.
- Supply Logistics: As larvae progress through the final instar, their consumption rate increases exponentially; ensure a 24/7 supply of fresh, pesticide-free plant matter to prevent “starvation stress,” which can prematurely trigger pupation.
Five Iterations of a Better Design
One of the most fascinating discoveries for young learners is that a caterpillar doesn’t simply grow larger.
It redesigns itself repeatedly.
Black Swallowtails progress through five developmental stages known as instars.
Instars 1–3: The Camouflage Phase
The youngest caterpillars resemble bird droppings.
It may not be attractive, but it is remarkably effective.
This disguise helps reduce predation during one of the most vulnerable periods of development.
Instars 4–5: The Expansion Phase
As they grow, the caterpillars undergo dramatic visual changes.
Bright green coloration emerges alongside distinctive black bands and yellow markings.
Food consumption increases rapidly.
Growth accelerates.
The system prepares for its largest transformation.
For children, this stage offers a powerful lesson:
Growth often requires change.
The version of ourselves that begins the journey is rarely the version that finishes it.
💡Just as the caterpillar repeatedly redesigns itself through growth, learners build new capabilities through cycles of challenge, reflection, and revision.
Read: The Maker Mindset: Building Growth Through Hands-On Creation
The Productive Struggle Before Transformation
Eventually, each caterpillar reaches a point where it stops eating.
It begins wandering.
To a casual observer, it may appear confused.
In reality, it is searching for the perfect place to build.
Once a suitable location is found, the caterpillar creates two critical structural elements:
- A silk attachment point called a button
- A silk support harness known as a girdle
Suspended by these simple biological engineering solutions, the caterpillar enters the chrysalis stage.
And then something extraordinary happens.
Inside the chrysalis, the caterpillar does not simply grow wings.
Much of its larval structure breaks down and reorganizes into an entirely new form.
It is one of nature’s most remarkable examples of transformation.
At Ascension Learning, we often describe learning in similar terms.
Real understanding is rarely built during moments of passive consumption.
It develops during periods of productive struggle, reflection, experimentation, and reconstruction.
Just as the caterpillar must pause before it can become something new, learners often need time to wrestle with ideas before genuine understanding emerges.
Data Integrity: Environmental Control
- Frass Management: Larval waste (frass) is a primary substrate for mold and bacterial growth; regular removal (daily or twice-daily) is essential to maintain a sterile, controlled experimental environment.
- Humidity vs. Airflow: While some humidity is required to keep plant matter fresh, excessive moisture creates the “mold variable” that can compromise the health of the chrysalis; always prioritize high airflow (mesh enclosures are preferred over glass jars) to prevent trapped air.
- Contamination Mitigation: Ensure that all introduced plant material is thoroughly rinsed to remove potential pesticides or competing organisms (such as predatory spiders), which can introduce external noise into your observation data.
What the Butterflies Taught Us
In the end, all three of our laboratory caterpillars successfully emerged as healthy Black Swallowtail butterflies.
Meanwhile, their counterparts in the garden continued navigating the challenges of the natural world.
Watching this process unfold changed the way our children interacted with nature.
The plants in the garden were no longer background scenery.
They became habitat.
The caterpillars were no longer insects.
They became participants in an observable system.
And the butterfly was no longer just a butterfly.
It became evidence of a successful build.
This shift—from observer to steward, from consumer to creator—is at the heart of meaningful learning.
When children care for living systems, collect observations, solve problems, and witness transformation firsthand, they begin developing the habits of mind that support science, engineering, and lifelong curiosity.
Understanding Is Built, Not Delivered
Whether a child is designing a bridge, creating a coding project, building a bee oasis, or raising butterflies, the underlying process remains the same:
Observe.
Question.
Experiment.
Reflect.
Build again.
The goal is not simply to accumulate information.
The goal is to develop the capacity to think.
The Black Swallowtail butterfly reminded us that some of the most profound lessons in resilience, adaptation, and design can begin on the underside of a single fennel leaf.
Sometimes the best makerspace is a garden.
And sometimes the greatest engineering project is already happening right in front of us.
Ready to Build Your Own Swallowtail Sanctuary?
Download our free Swallowtail Sanctuary Field Guide, featuring:
- A Junior Builder observation journal (Ages 3–6)
- An Advanced Architect engineering data log (Ages 7+)
- Builder’s Laboratory setup instructions
- Caterpillar growth tracking sheets
- Habitat design recommendations
- Reflection prompts that connect biology, engineering, and systems thinking
Because curiosity grows best when children have something real to care for.
And understanding is built, not delivered.
💡Research increasingly suggests that many of the capacities we associate with future engineers begin developing years before formal engineering instruction.
Continue: Can Preschoolers Be Engineers? The Cognitive Science Behind Early Makerspaces
Ready for the next project?
Explore more builder experiences:
- Bringing It Home: A Relatable Example – Bee Oasis
- The Future Builder’s Starter Kit
- Mini Architecture, Major Learning
- Exploring Google’s “Be Internet Awesome” Curriculum: Empowering Families
to Navigate the Digital World - Harnessing Machine Learning to Predict Air Quality: A Science Buddies
Project - How to Introduce STEM at Home: Fun Activities for Families
- #BuildYourWonder:
▪ Mini Maker Starter Kits
▪ From Couch to Creator: Hands-On Activities to Ignite Curiosity
▪ Raising Real-World Ready Learners
Because curiosity is only the beginning.
The real transformation happens when children start building.