Hawk moths in the Bahamas are the smallest ever found

Hawk moths, with a wingspan of over four inches, are among the largest night fliers in the insect world. Three new species from the Bahamas are breaking new records for size – but not for being large. Researchers at the Florida Museum of Natural History discovered the smallest-ever hawk moths that are about the size of a vitamin pill. 

“By comparison, we have a few other small hawk moths like the hummingbird moth, but of all of them these new species are the smallest,” said Deborah Matthews, a biological scientist at the museum’s McGuire Center for Lepidoptera and Biodiversity. 

There are 1,700 diverse hawk moth species worldwide. They have incredibly long proboscises, the straw-like tongues used to siphon nectar. The variation in tongue length is used to predict what local flowers the moths feed on. This method was first applied by Charles Darwin, who predicted the long proboscis after observing an orchid with unusually long nectar spurs.

The study began when Matthews and Jacqueline Miller reviewed the Florida Museum’s hawk moth collection to identify Bahamas specimens and sort survey material island by island. To differentiate closely related moths, researchers must study their anatomy. For Matthews and Miller, that meant making a detailed examination of the moths’ genitalia.

“You just can’t always make out distinctive wing patterns, whereas with genitalia you can cross-compare structures,” said Matthews.

The genitalia were dissected and observed under a microscope, and the differences were striking. This led to suspicions that they had discovered three new species. 

“In terms of moths, the giant silk moths and hawk moths are very popular and well-studied, kind of like the butterflies of the moth world. So, for us to find three new hawk moth species, that’s a really big deal,” said Matthews.

The Bahamas, with their proximity to diversity hotspots like Cuba and mainland areas of Mexico and the U.S., makes it easier for plants and animals to spread there, evolving into new species due to their isolation.

Island ecosystems are famous for organisms that far outsize their mainland relatives, like the giant tortoises on the Galapagos Islands and the Komodo dragons in Indonesia. However in The Bahamas species tend to be smaller, contradicting that giganticism trend.

Experts suspect that harsh weather could be the cause, as islands in the Bahamas archipelago are affected by Atlantic hurricanes and tropical storms. Heavy rain and windfall pose a threat to wildlife. It is likely that butterflies and moths with smaller wings are equipped to survive the intense winds. 

The research team believes that their work to identify these three new species will likely lead to more discoveries going forward.

The research was partially funded by the National Geographic Society. The study is published in the journal Insecta Mundi.

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By Katherine Bucko, Earth.com Staff Writer