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The weird creatures inhabiting the lava tubes of Hawaii

22 July 2022
3 minutes

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A planthopper nymph feeding on the sap of ohi’a lehua tree roots in a lava tube
A planthopper nymph feeds on sap from the ohi’a lehua tree roots. Planthopper nymphs produce wax filaments from a gland on their abdomen and make a wax cocoon that protects them from predators. Image: Alan Cressler 

Unearthing the endemic Hawaiian species that have adapted to life below ground inside lava tubes


Beneath the surface of Hawaii lies a subterranean world inhabited by pale, eyeless creatures. The volcanoes that created the island chain also built labyrinthine systems of lava tunnels that extend for kilometres underground. The upper reaches shelter bats and invasive species such as rats, but in the dark zones – the deepest regions of the caves – life has had to adapt. 

Recent exploration of caves on Big Island by a team of researchers from the University of Hawaii at Mānoa has already uncovered species that are new to science. In March, the team was awarded a US$1.29 million grant to continue studying life in the lava tubes. ‘It’s pretty fortunate to be on a research project where almost every time we go out into the field we actually do discover something new, whether it’s a new species or a range expansion,’ says assistant professor Rebecca Chong. 

The pale thread-legged bug, or 'assassin bug', found in the lava tubes of Hawaii
The thread-legged bug is a predatory insect endemic to the lava tubes of Hawaii. Image: Alan Cressler

Lava tubes are found where volcanoes produce low viscosity lava, particularly a basaltic type known by its Hawaiian name, pahoehoe. As it cools, it hardens and forms a crust, like ice over a flowing river. The molten core eventually drains away to leave a cavity that drips as it solidifies, leaving speleothems such as stalactites – or ‘lavacicles’ – helictites and soda straws. In Hawaii, the first colonisers of this space are the life-sustaining roots of the native ‘ōhi’a lehua tree, which break through the ceiling and hang like feathery curtains. Some time later, cave-adapted arthropods move in. 

Common features of such creatures include shrunken wings and elongated appendages – expanded non-visual senses suited for life in the dark. ‘Species range from sap-feeding insects, known as planthoppers, all the way to detritivores and omnivores, like crickets and millipedes, to a range of top predators,’ says Chong. Hawaiian varieties, including the blind wolf spider and the assassin bug, are found nowhere else. Their discovery is significant as the islands have already lost a lot of their endemic biodiversity. 

The four-year research project will document new species and their ranges to form a biodiversity baseline and help answer bigger biological questions about how these subterranean ecosystems form. ‘Our grant is primarily focused on the Big Island of Hawaii, because there is so much habitat heterogeneity, but we also want to use what we find to look at how that biodiversity scales across the islands. And then, hopefully, that information can also be used to compare and contrast other island lava tube systems,’ says Chong.   

A cave-adapted spider, and endangered and endemic species
The cave-adapted little-eyed big-eyed spider (it has tiny vestigial eyes, but is blind) is also endemic to Hawaii’s lava tubes. Image: Alan Cressler

The researchers will survey across five volcanoes on the island, ranging from those that just erupted to the very, very old. Big Island is the youngest island in the chain – it’s still forming – and lava tubes can be found in abundance. 

However, these ecosystems have a limited lifespan. Most lava tubes are less than ten metres from the surface and on the older islands, such as Kaua’i, many have weathered away. Life in the caves is intrinsically linked to the landscape above ground, making it susceptible to human activities, climate change and the increasing spread of invasive species. One, an aggressive fungal disease known as rapid ‘ōhi’a death, is already decimating the forests that provide a primary source of food for these underground worlds.

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Bryony Cottam
Bryony Cottam
Bryony wrote about sustainable tourism before joining Geographical as a staff writer in 2022. She writes the weekly Geographical newsletter and co-edits the monthly podcast.
Bryony Cottam
Latest posts by Bryony Cottam (see all)
  • The front line of climate change adapting to survive - 14 August 2022
  • Cryopreservation and nature’s SAFE - 8 August 2022
  • The weird creatures inhabiting the lava tubes of Hawaii - 22 July 2022
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Filed Under: Science & Environment Tagged With: August 22, Magazine, Volcanoes, Worldwatch

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  • About
  • Latest Posts
Bryony Cottam
Bryony Cottam
Bryony wrote about sustainable tourism before joining Geographical as a staff writer in 2022. She writes the weekly Geographical newsletter and co-edits the monthly podcast.
Bryony Cottam
Latest posts by Bryony Cottam (see all)
  • The front line of climate change adapting to survive - 14 August 2022
  • Cryopreservation and nature’s SAFE - 8 August 2022
  • The weird creatures inhabiting the lava tubes of Hawaii - 22 July 2022
  • Share
  • Twitter
  • Facebook
  • Pocket
  • Pinterest
  • Flipboard
  • Reddit
  • WhatsApp
  • Copy Link
Subscribe to our monthly print magazine!

Subscribe to Geographical today from just £3.40 per month. Our monthly print magazine is packed full of cutting-edge stories and stunning photography, perfect for anyone fascinated by the world, its landscapes, people and cultures. From climate change and the environment, to scientific developments and global health, we cover a huge range of topics that span the globe. Plus, every issue includes book recommendations, infographics, maps and more!

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