CAVE CONSERVANCY OF HAWAI‘I

WITH YOUR HELP, WE CAN PROTECT
HAWAII’S LAVA TUBES.

Biology of Lava Tubes

Hawaiian lava tubes are home to unique fauna found no where else in the world
Portions of the following text and images were published in the Spring 2022 issue of the Hawaii Underground, the publication of the Hawaii Speleological Survey, as "A Field Guide to Identify Biology in Lava Tubes on Hawai'i Island," written by the HICAVES Team.

This is a guide to the biology of lava tubes in the Kīpuka Kanohina cave system in Ocean View, Hawai’i. However, many of the cave animal species found in Ocean View also live in other lava tubes on Hawai'i Island.
Most of the obligate, cave-adapted invertebrate fauna found in Hawaiian lava tubes are found in association with ‘ōhiʻa tree roots. Roots are common features in lava tubes, including in tourist caves like Nāhuku (Thurston) Lava Tube in Hawai‘i Volcanoes National Park or Kula Kai in Ocean View. Native Hawaiian songs and stories highlight the cultural and spiritual importance of ‘ōhi‘a.
The trees are vitally important ecologically throughout Hawai'i, in forests and deserts, because they provide food and shelter for native birds and insects.

Roots

Planthoppers

Many of the lava tubes have roots that are from the native pioneer tree, Metrosideros polymorpha, referred to by the
common name, ʻōhiʻa lehua. 
Planthoppers are a keystone species in Hawaiian lava tube ecosystems. As specialist feeders on tree sap, they play an important role in cycling nutrients that originate from the surface world into the cave habitat. They are also important prey for many other species, being essentially sacks of sugar sucked in from tree juices. The fuzzy rear is wax that the nymph secretes to form a
protective nest as it matures into the adult form.
This image is of the nymph stage of the eyeless, pigmentless species, Oliarus polyphemus, found in nearly all caves
where suitable roots are present. 
Isopods or pillbugs are crustaceans that feed on detritus, like rotting root material. Along with root sap, detritus is one of the major ways that nutrients are brought into and recycled in these lava tube ecosystems. Native isopods, like this one, have tiny eyes and bumpy ornaments all over their backs. 

Isopods

Crickets

The pictured isopod is likely in the genus Littorophiloscia,​ a native genus to Hawai'i.
Cave crickets (belonging to the genus Caconemobius) are commonly seen hopping along the floor of lava tube passages. They can grow up to an inch long and are omnivorous insects. They eat root material and planthoppers. They are also one of the largest cave
inhabitants encountered.
This image is of the  species, Caconemobius, a native genus to Hawai'i. 
Native millipedes (belonging to the family Cambalidae) are another important group of detritivores commonly found on or around roots. The native millipedes in the genus Nannolene have a row of dark orange spots that run down each side of the animal, one per segment. They can also be distinguished from non-native interlopers by the smooth rounded segments.

Millipedes

Moths

The pictured millipede is likely in the genus Nannolene,​ and is a native genus to Hawai'i.
The caterpillars of Schrankia moths look like inch worms as they move on roots and rock surfaces. They hatch, feed, and metamorphose on the roots. Their cocoons, which look like shredded roots bundles, can be seen hanging amongst wet, live roots. The adult moths
can fly and may even leave the caves. However, very little is understood about the adult part of the moth life cycle and ecology. The most common species, Schrankia howarthi, has two forms. The dark zone morph, is lighter in color, has reduced eyes, and is typically flightless. In contrast, the twilight zone morph looks similar to others in the genus and retains the ability to fly.
This image is of the  cave moth, Schrankia, likely Schrankia howarthi.
Cave wolf spiders (Lycosa howarthi) are the largest animals commonly found in Kīpuka Kanohina, reaching over three inches in diameter (including legs). One of the key adaptations to the cave environment is their reduced eye size (even if you can see all eight of them!) when compared to surface relatives. These spiders are the top predators in the lava tubes, at least in the Kīpuka Kanohina. The closest relative to this species is the cave-adapted and federally endangered species, Adelocosa anops, from limestone caves on Kaua’i.

Spiders

Thread-legged bugs

The pictured wolf spider is Lycosa howarthi, a native genus and species to Hawai'i.
Thread-legged bugs (in the genus Nesidiolestes) are another top predator. They are usually found in the upper reaches of roots and the cave roof, and use their long, mantis-like legs to stalk their prey. This genus was originally described from Emesine Cave, on the other
side of Hawai’i island and in a lava flow younger than Kīpuka Kanohina.
This image is of the  thread-legged bug within the genus Nesidiolestes, native to Hawai;i.
The cave treader (belonging to the genus Cavaticovelia) is a cave-adapted relative of surface water treaders. Like its surface relatives, this species appears to favor damper
areas of cave walls and floor. Another important cave predator, the cave treader uses its piercing mouthparts to suck its prey dry.

Cave treaders

Beetles

The pictured cave treader is in the genus Cavaticovelia, which is native to Hawai'i.
Paratachys aaa is a small carabid beetle found only in caves on Hawaiʻi. Despite being half the size of a grain of rice and with reduced eyes, chemical analyses of the diets of these tiny creatures show them to be important predators in the cave ecosystem. Their likely food sources are springtails or mites. These beetles are often found around dead, disintegrating roots on the floor and lower walls of the cave.
This image is of the  cave beetle, Paratachys aaa​, a native species to Hawai'i.
Terrestrial cave amphipods are detritivorous crustaceans. They can be found under rocks in damper areas of cave passages and hop away if startled. The closest relative to those found in Kīpuka Kanohina are on Kaua’i and belong to the genus Spelaeorchestia. The species on Kaua’i is federally protected as an endangered species. This species, S. pahoehoe, was recently described (in 2023) and is found only in caves in southern Hawai'i Island, including in only a few sections of Kīpuka Kanohina and nearby in lava tubes within the Kahuku unit of Hawaii Volcanoes National Park.

Cave amphipods

Springtails

The pictured cave amphipod is Spelaeorchestia pahoehoe, a native to Hawai'i Island.
Springtails (belonging to the subclass Collembola) are tiny detritivores, attaining a size of up to half a grain of rice. It is still unclear how many species occur in Hawaiian lava tube passages. They are found in all parts of the cave but are most abundant in damp areas with rotting plant debris. They are called springtails due to the furcula structure at the end of their abdomen. When released, this snaps against the ground and pings the springtail
away from danger.
This image is of a tiny springtail found in Hawaiian lava tubes and likely a native species.​
There are different types of centipedes found in Hawaiian lava tubes. There are centipedes with long, narrow bodies that belong to the order Geophilomorpha, which are common soil inhabitants and can occasionally be observed in the caves. Another centipede encountered in the lower portions of Kīpuka Kanohina is shorter and has
broader body segments. This one is in the family Lithobiidae. Centipedes are predators and eat planthoppers and other species living on the roots, or anything they can find. Watch out! 

Cave centipedes

The pictured centipede is within the family Lithobiidae, but has not been described to the genus or species.
The text and images were designed for this website by A.S. Engel, who acknowledges the National Science Foundation for supporting the study of lava tube biodiversity on Hawai'i Island (DEB-2204671) and the Cave Conservancy of Hawai'i for field assistance during the research.