What is a Butterworm?
Butterworms are most well known for their usefulness as fishing bait, although, they are also highly valued as a reptile feeder species. In fact, they are great as a feeder insect particularly due to their bright color and attractive scent that makes them a tempting snack to even some of the more stubborn pets. The allure of this species is that they are quite mysterious – very little is known about this insect, given that they are raised successfully only in Chile (the country they are native to). Essentially, any time they are used elsewhere, whether as fishing bait or reptile food, they are an imported product.
The butterworm is the larval stage of the Chilean moth, Chilecomadia moorei, and is also known as Tebo worms or sweet worms. It is an average-sized species of caterpillar, reaching lengths of approximately 1.75” long. Their bodies are typically a rich orange to red color with spots aligning their sides – this is part of what makes them a great feeder insect, as reptiles in captivity can easily spot them. They are also quite slow-moving, making them easy to catch by even the slowest pets.
The Chilean government holds tight regulations over the butterworm. They do not allow for this species to be reproduced elsewhere and go to great lengths to ensure it. This is because, when they reach adulthood anywhere outside of their native country, they are considered to be a pest. As a pest, the butterworm can wreak severe havoc on ecosystems. Even in their home country, they are considered a pest that has reportedly devastated Eucalyptus plantations over the years.
In Chile, the butterworm feeds only on the Trevo plant, Trevoa trinervis, a plant native to the central region of Chile. (This is part of why they are difficult to raise in captivity – apart from governmental regulations, this feeder insect has a highly specific diet that keepers may struggle to sustain.) In other countries, though, they are more readily recognized by their genus, Chilecomadia, rather than their particular species. For instance, although it is known the butterworm’s adult form, the Chilean moth, is a pest in its own right, it is most often discussed in the context of a larger group of Chilecomadia pests, including:
Collectively, these are referred to as the cossid moths and were discovered as far back as 1860. The butterworm is among the most recently discovered, however, only dating back to 1915. This may be part of the reason why there is so little known about the species.
It is unclear why this moth is so much more tightly regulated than all others – after all, numerous moth species around the world have been determined to be pests. Additionally, it is not the only feeder insect that is distributed outside of its native country. Several feeder insects originated in countries separate from where they are sold, and even cultured by hobbyists and scientists alike. Well-known examples include the silkworm, a species native to China, and the mealworm, native to many African countries. These feeder insects are distributed worldwide and do not face the same stringent regulations that butterworms do.
Life Cycle of Butterworms
There is very little known about this species in general, even less so about its life cycle. When they are shipped anywhere outside of Chile, Chilean law does not allow for the butterworm to reach adulthood as a method of preventing their spread as a pest species. Instead, they are allowed only to be kept as larvae. Since they are a moth, however, we do know the basics of their life cycle in that they undergo complete metamorphosis, having four distinct life stages (and sub-stages known as “instars” during larval development).
Egg: Hundreds of eggs are laid on their food source, the Trevo bush, Trevoa trinervis. Moths generally lay their eggs individually on either the upper or lower surface of the leaves of any host plant. The average moth egg takes slightly less than two weeks to hatch and release the next development stage, the larva.
Larva: This is the recognizable life stage that most people can identify. In the wild, the larvae will feed on the Trevo bush for several weeks as they go through each instar, molting as they grow. Unless there is a loss of nutrition or another natural event that prevents the larvae from gaining sustenance from their host plant, they will remain on the same bush until they are ready to pupate.
Pupa: The exact type of pupation that butterworms go through is unclear. Whether they construct a cocoon around themselves like many other species or simply drop into the soil like hornworms is not widely known. Still, the average moth takes from as little as 5 days to an average maximum of 21 days to emerge into adulthood.
Adult: After pupation, the adults live only for a short time to mate and reproduce and begin the cycle all over again.
Butterworms are from the central region of Chile and can only be found near their only food source, the Trevo plant. If for any reason they are present in other countries’ habitats, they are considered an invasive species and can be quite destructive to native ecosystems. In Chile and other South American countries, butterworms are notorious for wreaking havoc on eucalyptus plantations.
How to Raise Butterworms
Butterworms are quite difficult to keep in captivity (if you plan to raise them throughout an entire life cycle) Unfortunately for those reptile-owners that do not live in Chile, they do best in the environmental conditions of their native country, and with access to their native diet. Currently, they can’t be found in hardly any other country – even scientists have a hard time getting their hands on them! Those that can successfully obtain the mysterious butterworm can only do so by importing them directly from Chile.
Additionally, Chilean law mandates that butterworms are irradiated before shipping. This prevents them from pupating into a moth to avoid them ultimately escaping and becoming a pest to other countries. (It is for this reason primarily that they cannot be cultured by the home keeper.)
With all of this considered, if you wish to keep butterworms in captivity, you will be most successful in keeping them only in their larval stage. They are most often sold in a state that does not require any feeding whatsoever (although it can’t hurt to give them something to nibble on now and then).
Note that anyone claiming to have successfully raised butterworms outside of Chile may be doing so illegally and this is not something you should attempt to replicate.
Housing and Maintaining Your Butterworms
Once you receive your order, fortunately, there is not much you have to do! Your butterworms will arrive in a small plastic container layered with a dry, organic substrate. (If you wish to make your own, you can replicate this substrate with wheat bran or similar dry food.) When your butterworms are set with their substrate, you simply place them directly into the refrigerator and check on them in approximately one hour.
Note if they are beginning to web the substrate together – if they are, this is a great sign and you can leave them be. If they are not, however, this is an indication that the substrate is not suitable to their needs and can most likely be attributed to dampness. You must get rid of any excess moisture as soon as possible, as this may lead to the development of fungus and bacteria that can endanger your butterworms. When their container is back to ideal conditions, you can leave them in the refrigerator and they will persist anywhere from 1 to 4 months, existing in a hibernated state.
Butterworms are a feeder species that – although they offer great moisture and protein – may not be the best option as a staple for your lizard (especially bearded dragons!). Because of their high fat content, they instead make a great periodic snack.
They are difficult to track down commercially and will almost always be sold as an imported product. If you wish to raise your own colony of butterworms, you must be responsible in your search for a supplier, as they are legally required to be irradiated before shipping. It is for this reason that, if you decide to keep them, you will be maintaining them only in a hibernated state as larvae. Still, because of how long they last when refrigerated, they can be quite rewarding to keep as an addition to a well-balanced diet for your reptile.