The Multifaceted Venom of Velvet Ants: Nature’s Swiss Army Knife

Only a few beings can confront a velvet ant and emerge unharmed. These ground-living insects are not true ants but are instead parasitic wasps recognized for their intense stings.

Recently, investigators have found that these wasps don’t inflict suffering uniformly across all species. Various components in their venom blend accomplish the task depending on the target of the wasp’s sting, as detailed by researchers online on January 6 in Current Biology.

Among the most well-armored insects, velvet ants possess not only venom but also warning coloration and scent, an exceptionally resilient exoskeleton, an elongated stinger, and the capacity to “scream” when agitated. In 2016, entomologist Justin Schmidt remarked that being stung by a velvet ant was akin to “hot oil from the deep fryer cascading over your entire hand.” Researchers have also discovered that other vertebrates, including mammals, reptiles, amphibians, and birds, respond to the wasp’s sting.

Other organisms are recognized to possess this kind of “broad-spectrum” toxin — a recent investigation uncovered a centipede with a venom blend that alters based on whether the insect acts as predator or prey. However, it is still uncommon for a single organism to repel animals from various classifications, states Lydia Borjon, a sensory neurobiologist at Indiana University Bloomington. In some instances, investigators have identified generalized venoms that target molecular structures shared among different classes of animals, inherited from their last common ancestor long ago.

When Borjon and her fellow researchers initially began testing velvet ants, they theorized that their venom might be similar.

“If you’re attempting to defend against various predators, then it would be logical for the venom to be generally effective by focusing on something quite ancient,” Borjon explains. “Ultimately, what we discovered was different and unexpected.”

The group gathered venom from scarlet velvet ants (Dasymutilla occidentalis) and formulated synthetic versions of its 24 peptides, the primary chemical constituents of the venom that cause pain or otherwise disrupt cellular functions. By evaluating the entire cocktail and the individual peptides on the neurons of larval fruit flies, the scientists were able to identify an insect-specific reaction to the most prevalent peptide, referred to as Do6a. It seems to target a type of neuron that responds to harmful stimuli.

When the researchers performed the identical experiment on mice, the synthetic venom still triggered a painful reaction — but this time, it wasn’t mediated by Do6a. Instead, the discomfort appeared to originate from two peptides that are less common in the venom, Do10a and Do13a, which elicit a wide-ranging and diffuse response across several types of mouse sensory neurons.

Combined, Borjon states, the results demonstrate that velvet ant venom causes pain in mammals — which collectively possess similar pain pathways — through a more generalized mechanism, whereas the venom’s influence on insects is more customized to a specific target.

This research stands among the first to showcase multiple modes of operation within a singular venom and is “a significant ‘first pass,’ employing some innovative techniques to investigate a fascinating inquiry,” claims Sam Robinson, a toxinologist at the University of Queensland in Australia.

However, the results may be more prevalent than they appear, he remarks. There’s minimal scientific motivation to examine the effects of most venoms on different species, especially if a species is a prey specialist, “and so while this may seem unique, it’s difficult to assert with certainty,” Robinson notes.

The investigation also contributes to another perpetual enigma surrounding the velvet ant: Why it appears to possess numerous defenses. Despite their extensive defensive capabilities, nothing consistently consumes them, nor are velvet ants themselves aggressive hunters, states Joseph Wilson, an evolutionary ecologist at Utah State University in Tooele.

The fact that the ant’s venom seems to “pack a genuine punch” against other insects indicates that interactions with some unidentified insect predator — either historically or currently — might be propelling the evolution of these characteristics, Wilson suggests. Alternately, it could merely be a fortunate accident of evolutionary processes. “As evolutionary biologists, we endeavor to attribute some intent behind these adaptations, but evolution occasionally unfolds in enigmatic ways.”