If you have attracted butterflies to your garden by providing the plants they eat (host plants), you have very likely had the experience of a Disappearing Caterpillar.
Since many of us, myself included, began our butterfly gardening journey with milkweed to feed monarchs, this is the caterpillar photo that is most commonly found on milk cartons. However, if you have advanced to other species, you are aware that ANY type of caterpillar can seemingly disappear one day.
It is typically the case that you have seen the caterpillars happily eating on the plant for days. Maybe you even noticed them in their egg stage, before they became caterpillars. You see them grow, and molt and you become fond of observing their progress. They are your friends. Then, one day, you go to visit them and they have vanished without a trace.
It should be noted that with few exceptions, caterpillars DO NOT intend to leave their host plant. Their intuitive mother laid her eggs on or near that plant for a reason, they need it to survive. Ideally, they will stay on it, eating its leaves for the remainder of the caterpillar mode of their lives. They will not naturally wander except in these circumstances:
Sometimes weather, a predator or something else knocks them off of their plant. in this case they don't have navigation skills to help them get their bearings and find their way back. They may starve if they don't find the plant, or one like it, to finish developing on.
Occasionally, a caterpillar may wander away from the plant to molt. It may go to a nearby fence, branch or plant and then return back to the host to continue eating.
If the host plant was unhealthy, withered, infested or otherwise compromised, they may have been forced to wander off to find a more suitable food source. If the plant is not healthy, they cannot be either.
Once they have eaten enough, and gone through all of their instars successfully, they will sometimes wander off of the plant to pupate elsewhere. I have found that some species often pupate right on the plant, but some are more prone to wandering away. This is a happy ending and what we want as butterfly gardeners!
Like so many things in life, there could be lots of things going on, and some of them even simultaneously. Here are some additional plausible explanations, in no particular order, as to why you aren't seeing caterpillars on the plant that you recently saw them on. Warning, these bullet-points aren't all easy to read if you love your butterflies.
It could be that they are outsmarting you by hiding or with other camouflage techniques. Some species can change in appearance from one molt to the next. They could be hiding under a leaf out of sight. They could have pupated already and their chrysalis may be camouflaged in such a way that you aren't noticing it.
They may have been eaten by a predator. We don't typically like this answer but it is what it is. Butterflies are the bottom of the food chain and can be eaten by birds, snakes, frogs, lizards, ants, wasps, dragon-flies, other caterpillars, rats, bats, mice, racoons, and more.
Sometimes caterpillars can be infected with a virus and if this is the case, the virus can "take over their bodies" and make them do curious things that they wouldn't normally do.
Those are the most obvious causes of disappearing caterpillars.
As you practice observing and rearing them, you will improve at your ability to assess the situation.
What can you do about disappearing caterpillars? Honestly, it is helpful to note that in nature there are always ebbs and flows. You win some, you lose some. This isn't an issue that we can easily control.
Many people choose to rear caterpillars inside in containers. That is an option, but it requires much more work and attention. Even then, the caterpillars face dangers that we cannot protect them from, so it is not a failsafe way to rear a healthy butterfly.
So, enjoy the caterpillars while you have them. They grow up so fast and then, one day, just like that they are gone.
Maybe they didn't disappear, maybe you just cannot see them.
Maybe they met their fate with some peril.
Maybe they have gone on to be a glorious butterfly.
Empty Nesting,
Jessica
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