View attachment 832119 American Dagger (
Acronicta americana)
IMO poisonous is a questionable term to use in this Noctuidae's case. More common in common terms is that they have stinging hairs. FWI, urticating setae are subjective when it comes to how individual people react to them, and depends on what they are susceptible to. The term is derived from Urtica (Latin for the Nettles), a genus of plants where some of its species hare hairs that can 'sting' you, especially if contacted in soft skin areas (between fingers, back, etc). In the US species the discomfort varies from species to species, from all but unnoticeable to irritating and in the tropics to dangerous. Most urticating caterpillars in the US are from less than to no worse than tangling with a stinging nettle species (ie,
Urtica diorca). The most notorious in the US for its painful sting is the Saddleback (
Acharia stimulea) that is widespread in the eastern US. But in the tropics there are caterpillar species that are cryptic and gregarious that if heavily stung by enough of them can become an emergency that can lead to death.
The Saddleback's range... Since they are polyphagous feeders they can be found in many different habitats.
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Here in the west the Hemileucinae (Buck Moths) are notable stingers. Their sting is reminiscent of stinging nettles, but with a soft touch they can be picked up with the pads of your finger tips without getting stung.
A western species... Hemileuca electra electra (
Saturnidae)
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