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Up Close and Personal With Venomous Moths

Lonomia electra larvae

An army of toxic spines of the moth Lonomia electra congregate on the author’s hand. (Photo credit: Bart Coppens)

By Bart Coppens

“Assassin caterpillar” or, in Spanish, “taturana”—these are the names appointed to caterpillars of the genus Lonomia. It’s a name rightfully deserved: Species of the South American genus Lonomia are of medical significance due to their larval forms that may cause severe envenomation and even death to humans. Lonomia is often considered to be the most venomous genus of Lepidoptera, in particular L. obliqua, of which the hemotoxin is known to inflict severe envenomation and cause disseminated intravascular coagulation and haemorrhagic disease in victims.

Bart Coppens

Bart Coppens

Despite their medical significance, not much is known about Lonomia species’ life cycles and biology. The deadly hemotoxic effects of Lonomia caterpillars have only been scientifically described in two species, namely the L. obliqua and L. achelous, while the genus currently contains 32 described species.

First, it is important to know that the potential deadly hemotoxic effects suffered by victims of larval stings also have a positive side: The potent blood thinning property of the toxins may have several interesting medical applications, which is the reason several laboratories around the world have already started to look into the venom.  This, combined with their medical significance, gives us all the more reason to study these moths.

In the latest study, we explore the life cycle of the L. electra from Costa Rica, delve into the life cycle of these Saturniidae moths, share a few observations to spread awareness on Lonomia moths, and explain what motivates an entomologist to test the venom of potentially dangerous caterpillars on his own skin.

Lonomia electra skin irritation

Contact hives were suffered by the author after making skin contact with the spines of Lonomia electra. The sensation can be described as a burning, itching sensation, comparable to that of a stinging nettle that lasts for a couple of minutes. (Photo credit: Bart Coppens)

The subfamily of Hemileucinae among Saturniidae, consisting of roughly 630 species and unique to the continents of North and South America, characteristically contains larvae bearing toxic spines. Lonomia, often considered to be the most venomous, is included in this subfamily. After obtaining live material from Costa Rica, L. electra was bred in captivity for three generations, and the morphology and development time of all the early life stages (eggs, all larval instar, pupae) and even adult moths were recorded—a labor-intensive task considering the slow development rate of the larvae. (In captivity the larvae were reared from egg to pupae in about 130 days’ time on the host plant Ligustrum ovalifolium).

Lonomia electra adults

All three adult forms of Lonomia electra: On the left and middle are the two color forms of the male, which is dimorphic and has a distinct brownish and yellowish form. On the right is a female, which does not seem to be variable and always has a rather grayish appearance, in contrast with the males. They make excellent leaf mimics. (Photo credit: Bart Coppens)

The highly gregarious larvae demonstrate social behavior and travel and feed together in large groups. Larvae were tested by carefully pressing and rubbing the venomous spines of each larval instar on the author’s skin. In regard to safety, larvae were first tested carefully by making contact with only a few spines at the same time and looking for hemotoxic effects, increasing the surface area (and thus dose of venom) over time. Most incidents of victims suffering serious envenomation are due to coming into contact with larger congregations of these larvae. Interestingly, after carefully testing, the effect of the venomous spines on human skin, this species demonstrated no hemotoxic effects in the form of bruises or internal bleeding, though a burning sensation and contact hives were experienced.

Clearly, the effects of the toxins of Lonomia seem to be very variable per incident and per species, if we compare this to some species in literature. Hopefully, investigations will continue and more information will be revealed about the nature and properties of the venom of the larvae of these incredibly fascinating moths.

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Bart Coppens is an entomological researcher in The Netherlands. Email: Website:


  1. Maybe I won’t retire to Costa Rica. We have several stinging caterpillars here in Florida. They are painful. But nothing like this. Interesting article. Thanx.

  2. The curious mind. I found a cocoon as big as my hand. I could feel it moving when I held it in my hand. It went silent in the Winter. Emerged in the Spring. A Cecropia moth. Took it to a high, abandoned park in NYC. It clung to my hand hard and stretched and fluttered its wings. I was scared and wanted to shake it off, but I held fast. It flew off into the trees. I understand.

  3. My grandmother who was from Costa Rica told me that moths can cause skin discoloration. Do you know if that’s true?

  4. Followed author for awhile on social media (haven’t used in many moons) and loved the moth stuff. Glad to have stumbled on this and recognized the name during my random moth googling!

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