Butterflies Prove Complex Learning May Be More Common in Insects Than We Thought

It's easy not to think much about the intelligence of insects. Tiny creatures with even tinier brains—how smart can they be?

But as biologists begin to rethink how animals think, even insects are being seen in a new light. Now a new study from the University of Bristol finds that Heliconius butterflies are capable of spatial learning.

The results provide the first experimental evidence of spatial learning in any butterfly or moth species.  

We have known about spatial learning in insects, but mostly in ant and bee species that live socially in a communal nest. However, as noted by the University, the new research suggests that "complex learning skills, such as the use of spatial information, may be more common in insects than previously thought."

“It’s fascinating to learn about the complex behaviours that even familiar animals like butterflies express as part of their natural ecologies," says senior study author Dr. Stephen Montgomery of the University of Bristol’s School of Biological Sciences. "These species are extracting and processing diverse information from their environment and using them to perform complex tasks—all with brains a couple of millimetres wide.” 

The team set up spatial learning experiments in Heliconius butterflies over three different spatial scales, each representing ecologically-relevant behaviors.  

They started small, testing to see if the butterflies could learn the location of a food reward in a one-square meter area containing 16 artificial flowers, which would represent foraging within a single resource patch.  

Then they increased the spatial scale to see whether Heliconius could learn to associate food with either the left or right side of a three-square meter two-armed maze.

Finally, they increased the distances again using large outdoor cages to see if the butterflies could learn the location of food in a 60-meter-wide T-maze.

The butterflies were successful in all three scenarios.

“Wild Heliconius appear to learn the location of reliable pollen sources and establish long-term ‘traplines,' says Montgomery. “Traplines are learnt foraging routes along which food sources are repeatedly returned to over consecutive days, an efficient foraging strategy similar to the behaviour of some orchid bees and bumblebees. However, the spatial learning abilities of Heliconius, or indeed any butterfly, had not yet been experimentally tested.” 

The findings also suggest that Heliconius may be able to learn spatial information at even larger scales.

Next, the researchers plan to look into Heliconius' relative proficiency at spatial learning versus closely related species that don’t feed on pollen. "This would help to reveal how the evolution of enhanced cognitive abilities can be shaped by an animal’s ecology," explains the University.

The team also plans to study just how Heliconius manages to navigate its way through the world. It is believed that visual cues, such as panoramic views, play an Important role in this—but they may also rely on other cues, such as the sun or geomagnetic compass.  

“It’s been almost a century since the publication of the first anecdotal story on the spatial capabilities of these butterflies," says co-lead author Dr. Priscila Moura from Universidade Federal do Rio Grande do Norte. "Now we are able to provide actual evidence on their fascinating spatial learning. And this is just the beginning."

The study, "Rapid expansion and visual specialisation of learning and memory centers in the brains of Heliconiini butterflies," was published in Current Biology.