I just found a caterpillar! What do I do?

"I found a caterpillar!" The wonderment of it all…but now, what to do?

Do you remember back when you were a child and you found a caterpillar? What did you do with it? Chances are you put it in a jar (washed peanut butter of mayonnaise, I bet). You then added some grass or leaves from the garden and a stick for it to climb on. Did I guess correctly? Then, that poor little caterpillar ended up…dead. Hmmm…why did this happen?


The first thing you need to know is that butterflies are VERY specific about what plants they oviposit (lay eggs) on which means their babies (larvae aka caterpillars) will only eat very specific plants! Here, a mama Gulf Fritillary oviposits an egg onto a Passiflora leaf.

That means if you have 'found a caterpillar' you will need to make sure you are very careful in observing exactly WHAT plant that caterpillar was on when you found it because, that plant is its 'host plant.' Feeding it the wrong food will KILL the little guy. Sure, sometimes a caterpillar will wander onto a plant that is not its host plant (baby food). It might have fallen off its host plant or was on its way to pupate…

Be sure to look at all the plants in the vicinity of that caterpillar. This will help you in identifying what type of butterfly baby you've found as well as what type of 'baby food' you need to feed it. All those times you fed your caterpillar grass is why the poor dear died!


You can put the caterpillar in a jar (yes, those peanut butter jars will work!) or even something as simple as one of those Gladware cups. These recycled containers make excellent rearing containers for caterpillars. Even those plastic clamshell-type of fast-food containers can be used as a caterpillar habitat! There's no need to poke holes in the jar lid as long as you don't seal it completely.

Caterpillars don't have enough (usually!) strength to push the lid off of a container. Just make sure you aren't sealing the container completely (in other words, Tupperware probably is NOT a good choice for a rearing container).Plastic shoes boxes work well if you have a lot of caterpillars to raise. Just place a folded sheet of paper towel along the bottom; this will help when you clean out the frass (poop).

Keep the caterpillar rearing container out of direct sunlight. Provide fresh leaves (from the host plant). Dried out/dehydrated leaves are just not appetizing and won't keep your caterpillar alive anyway. (Would you want to eat dried up lettuce?) If you want to include a stick or two, go for it.

A few key points: Be sure to throw out all the frass (caterpillar poop) each day. Leaving the frass in the jar is 1) unhealthy, 2) can build mold, 3) is just plain disgusting! Moisture is another no-no as it increases the chance of bacteria and virus growth. So, keep that jar away from sunlight!

Caterpillars generally do nothing more than eat and poop, eat and poop, molt (shed their exoskeleton) several times, eat and poop some more for about two weeks. Then, they decide it is time to pupate and they stop eating.Here is a Gulf Fritillary larva that has just molted. You can see its exuvia (shed skin) to the right.



NOTE: If you find your caterpillar has not eaten for a bit do not worry! It may be getting ready to molt! Caterpillars shed their skin (molt) about five times before they pupate. When they are ready to molt they often do not eat but just kind of 'hang out.' Don't bug 'em but let 'em be. That freshly-shedded skin won't be around long because the caterpillar usually turns around and EATS IT! Eeeeuw! The 'new' skin is damp and fragile until it 'hardens.'


When your caterpillar decides it is time to pupate it will stop eating. Some caterpillars hang upside-down, pupating with its head down (some people call this the 'J' position). Others form a sling or harness and hang at a diagonal, head up (swallowtails generally pupate head up with a sling). But, keep in mind that EVERYONE is different! Some, who you know are 'supposed' to hang in a sling at a diagonal will decide to hang from the ceiling…

It can take several hours to over a day before a caterpillar completes pupating. This is when it molts the final time. The last thing you will probably find is its head capsule. (This is a cool looking thing if you look at it close-up.)


Now, this is where things can get interesting. MOST butterflies will eclose, after undergoing complete metamorphosis, in two weeks. SOME can go into diapause (commonly referred to as overwintering) where they remain a chrysalis/pupa for up to a year or more! (Yes, I've had some Pipevine Swallowtails that were pupae for over 14 months.) Just like human children, butterflies are all individuals and will do things in their own time.

Upon eclosing (coming out of the chrysalis) it can take upwards of four hours for the butterfly to stretch out and inflate its wings, and getting its wings to harden. The larger the butterfly, the more time it needs after it ecloses. This is why having a larger rearing container is better than a smaller one. (More info on rearing containers to come…)

When your butterfly has hardened wings, it is ready to let go!


Be sure to release the beauty when the weather is dry (no rain) and warm. Butterflies are cold-blooded and need the warmth to help them fly.

Whew! Did you get all of that? If so, then you are set to get started!