Monarch Butterfly Caterpillars Eat Pumpkin

Jacqui Knight of Monarch Butterfly NZ Trust shared the fact that Monarch larvae will eat pumpkin and other relatives of pumpkin in the cucurbita part of the gourd family. Due to Jacqui’s sharing of information, many people have fed pumpkin to large caterpillars. Pumpkin eating was reported as early as 1964 in New Zealand.

So far reports are that if late instar caterpillars are fed pumpkin, they will pupate and emerge apparently whole and healthy. We used ordinary Jack-O-Lantern pumpkins and have also used ordinary salad cucumbers. If you find something in this family that works well and would like to share it, please send us the name of the item you used and photos if you have any to share. Remember to wash them thoroughly if you aren’t going to peel them! If Bt was used on them, they can be deadly to caterpillars, even if certified organic.

There is a double challenge when we try to coax larvae into eating something other than their normal food.

There are two instincts that must be overcome.

1) The first is the bite instinct.

If we are offered good food (chocolate pudding and pie) that smells like dog poop, we will NOT take a bite. For some reason, Monarch caterpillars will take a bite of pumpkin, cucumbers, and a few relatives of these foods although it isn’t their host plant, milkweed. Somehow, that bite instinct is fooled.

2)The second is the swallow instinct.

If that chocolate pudding and pie looks great and smells great, we will take a bite. If it is full of salt instead of sugar, though, we will not swallow. We will spit it out. The swallow instinct is NOT engaged.

Monarch caterpillars will not only bite but will swallow pumpkin although the taste is not the same as milkweed (not by a long shot). The swallow instinct is also fooled.

Please take note that pumpkin will mold quickly. Watch a closed or semi-closed conatiner closely for mold. Mold can kill caterpillars.

The question is whether eating pumpkin actually keeps them alive longer. At Shady Oak we will be doing further tests and will report our findings later.

If it does keep them alive longer and they grow on pumpkin or cucumber, emergencies when teachers and others cannot find milkweed for their late instar caterpillars will no longer be true ‘emergencies’. Although milkweed is absolutely best, if using pumpkin or cucumber in a tight situation can save the lives of Monarch butterfly caterpillars, life will be easier (and less expensive) for teachers and others who run out of food for their caterpillars.