— This article by Jerry Cates, first published on 7 March 2010, was last revised on 6 July 2012. © Bugsinthenews Vol. 11:03(10).
Though most of the reports I receive on puss caterpillars describe the excruciating pain their stings cause, some tell me how they touched, even played with, these caterpillars without receiving any ill effects. Often, the person reporting such an event seems to believe that they might be one of those fortunate individuals who happens to be immune from the puss caterpillar’s toxin.
Genuine immunity to puss caterpillar toxin has never been demonstrated. However, it is known that some puss caterpillars are unable to sting. Thus, if you happen to be one of those who has picked up a puss caterpillar without being stung, beware! The next puss caterpillar you handle may send you into paroxysms of agony.
Why some puss caterpillars do not sting is a mystery. I have not yet conducted a scientific study designed to produce answers to that specific question, though it would be possible to grade individual caterpillars according to the potency of their venom and the effectiveness of their envenoming structures. Barring that, it can be speculated that a number of possibilities seem more likely than others. Genetic abnormalities top the list. The toxin delivery system in the puss caterpillar depends on a number of subsystems, all of which must work effectively for the caterpillar to sting. Just as some people are born without skin pigment, or with deformities of one kind or another, certain puss caterpillars may be born with one or more of the venom delivery subsystems missing or defective. In some cases, all subsystems may be in place but the venom produced by the venom glands is chemically benign.
Such genetic defects often work in favor of the organism, especially when the organism has a reputation for producing painful stings. That reputation will lead many caterpillar predators, such as birds, lizards, and spiders, to avoid attacking the puss caterpillar even if it happens not to be venomous, thus giving the defective caterpillar an advantage over its venomous siblings. Unlike them, it will be able to use the energy and resources normally invested in those structures for other purposes. Keep in mind, however, that the offspring of non-venomous puss caterpillar may be venomous.
Links: (1) Puss Caterpillar General Information. (2) The Puss Caterpillar’s Stinging Apparatus. (3) Puss Caterpillar Extermination. (4) The Puss Caterpillar’s Natural Predators. (5). Puss Caterpillar Stings–Medical Interventions. (6) Puss Caterpillar Stings–Home Remedy First Aid Measures.
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