When an antenna of the house cricket (Acheta domesticus) is touched with a heated probe, something curious happens: the insect turns its attention to the burned spot, grooming it repeatedly, for far longer than it would after a harmless touch or no contact at all. According to team of entomologists at University of Sydney, that behavior may be evidence of something scientists have long debated — that insects experience pain-like states.
Manzi et al. tested house crickets (Acheta domesticus), among the most widely farmed insects on Earth, for what is thought a key behavioral hallmark of pain: flexible, site-directed self-protection. Image credit: Matthew Lindsey / CC BY 2.0.
“Once dismissed as too small-brained or simple to support experience, insects are now known as capable of remarkably complex tasks, including associative learning, context-sensitive decision-making and cross-modal sensory integration,” said Dr. Thomas White, an evolutionary ecologist and entomologist at the University of Sydney, and his colleagues.
“Recent studies have also identified brain regions such as the mushroom bodies and central complex that appear to support evaluative processing functionally analogous to that seen in vertebrates.”
“Yet the question of pain in insects cannot be settled by neural architecture alone.”
“Given the diversity of nervous systems across phyla, and the sheer creative power of adaptive evolution showcased via multiple realizability, behavior remains our most direct and inclusive route to inferring experience.”
“That is, rather than asking whether an animal has the same hardware, the more relevant question is whether it shows a comparable behavioral profile under similar conditions.”
In their research, the authors tested 80 adult house crickets in a carefully controlled experiment designed to rule out simple reflexes.
Each cricket was exposed to three conditions: a soldering iron tip heated to 65 degrees Celsius (149 degrees Fahrenheit) applied briefly to one antenna, the same probe applied without heat, and no contact at all.
Cameras recorded every movement for 10 min afterward, and three observers — unaware of which treatment each insect had received — coded the grooming behavior frame by frame.
Crickets that received the noxious heat stimulus were significantly more likely to groom the affected antenna, devoted a greater share of their total grooming time to it, and kept it up for roughly four times longer than crickets in the no-contact control group.
On average, grooming of the burned antenna lasted about 13 seconds after noxious treatment, compared with around 3 seconds in the control condition.
“Crickets’ heightened grooming intensity followed a clear temporal trajectory: noxiously stimulated individuals showed an elevated, sustained phase that gradually declined, a pattern reminiscent of findings in bees and rodents,” the researchers said.
What makes the findings significant is not just that the crickets reacted, but how they reacted.
A reflex — the kind of automatic, unconscious withdrawal that even simple nervous systems can produce — would be expected to stop when the stimulus stops.
Instead, the crickets continued attending to the site long after the heated probe was removed, suggesting they were tracking something internally: a persistent, localized signal of harm.
“Pain remains one of the most elusive and consequential frontiers in animal cognition, and insects provide a particularly demanding test case,” the authors said.
“Behavioral evidence — particularly flexible, site-specific responses to harm — offers our most direct route to inferring pain-like states in these animals.”
“Our findings demonstrate such a response in the evolutionarily and commercially significant Acheta domesticus: crickets groomed a noxiously stimulated antenna more frequently, for longer, and with a distinct temporal profile compared with tactile or no-contact controls.”
“The response was both site-specific and persistent, suggesting that crickets monitor injury location and adjust their behavior in ways not reducible to simple reflexes.”
The study was published this month in the Proceedings of the Royal Society B.
_____
Oscar Manzi et al. 2026. Flexible self-protection as evidence of pain-like states in house crickets. Proc Biol Sci 293 (2070): 20260609; doi: 10.1098/rspb.2026.0609
