Plant diversity may explain why some caterpillars are fussy about their food

Many insects will eat almost anything in their sight, such as certain beetles, grasshoppers and locusts, while others are remarkably picky eaters. For example, numerous insect herbivores will feed only on a single plant family or a specific type of tree. But why is this so?

A new study published in the journal Nature Communications may have the answer, and it all comes down to temperature and plant diversity.

To find the answers, a small team led by Collin P. Gross, a biologist at Stanford University, studied global data sets of more than 10,000 butterfly species alongside more than 150,000 plant species, drawing on about 87 million field records.

The hungry and picky caterpillar

It was already known that insect species living near the equator tend to have more specialized diets than those living near the poles, and the researchers wanted to understand why.

The team compiled diet logs for thousands of butterfly species, which provided information on what they ate, organized into broad plant-family groupings. They then divided the world into a grid of squares, with each square measuring 100 by 100 kilometers (62 by 62 miles). For every square, the researchers mapped out the local caterpillar community. They focused on how many plant families the insects ate and how closely related those plant families were.

The next step was to link these diets to local weather data, including temperature and rainfall, before using advanced statistics to untangle how weather and plant variety interact to shape what they eat.

They found that in areas with an abundance of plant varieties, caterpillars were pickier. This trend was much stronger near the equator, in line with previous studies. The researchers suggest this is because, when so many options are available, caterpillars can afford to pick one plant family, master how to overcome its unique chemical defenses and avoid competing with other insects.

However, in hot climates, high temperatures were associated with broader diets. This is because temperature stress and seasonal limitations can force caterpillars to use a wider range of plants.

Even though heat forces caterpillars to be less restrictive, the massive variety of local plants has a much stronger impact, which is why tropical regions still end up hosting the pickiest caterpillars. "Our results reveal that global patterns in plant diversity, which are affected by climate, play a key role in shaping caterpillar diet breadth, while there also exist direct effects of climate on diet breadth that are comparable in magnitude to the direct effects of plant diversity," the study authors wrote in their paper.

There's always an exception

However, they discovered an exception on islands: "Here, global data shows that butterflies living with more plant families have narrower diets, while those on islands have broader diets."

The research team explains that islands are often populated by insect species that are more willing to eat a variety of plants to survive in their new home. However, there is an exception to this island. If an island is dominated by a native species (found nowhere else on Earth), the rule switches back. That's because these local insects have evolved in long-term isolation with a limited set of island plants.

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Publication details

Collin P. Gross et al, Climate and regional plant richness drive diet specialization in butterfly caterpillars, Nature Communications (2026). DOI: 10.1038/s41467-026-73236-4

Who's behind this story?

Paul Arnold

BSc Biology from University of London. BBC documentary producer with world travel experience. Freelances from southern Spain.

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