1. Primary succession after a volcanic eruption is a major ecological process, but relatively little is known about insects that colonize barren lava before plants become established.

2. On Hawai´i Island, the endemic cricket, Caconemobius fori Gurney & Rentz, 1978, is known as the first multicellular life form to colonize lava after an eruption from Kīlauea Volcano. In the Kona region, a congener, Caconemobius anahulu Otte,1994 inhabits unvegetated lava flows from Hualālai Volcano, but little has been documented about its distribution.

3. Our aim was to characterize the presence/absence of Caconemobius spp. across lava flows that are largely unvegetated, but differ in age since eruption and connectivity to older flows. We used baited live traps to survey 9 month–50 year-old Kīlauea lava flows for C. fori, and ~220 year-old Hualālai lava flows for C. anahulu.

4. We found no evidence that C. fori has colonized the Kīlauea flows from the 2018 eruption. However, we did discover that C. fori was persistent and widespread on Kīlauea lava up to 50 years old within Hawai´i Volcanos National Park. We also captured C. anahulu across much of the Hualālai lava flows we surveyed in Kona.

5. We demonstrated that C. fori do not always arrive on new lava within months after an eruption, in contrast to previous reports, and that both C. fori and C. anahulu can remain on lava longer than previously appreciated. Vegetation successional state may be more important than true age for the persistence of these endemic crickets.

Detailed methods can be found in Heinen-Kay et al. (2021) Ecological Entomology. In short, we sampled for two species of endemic Caconemobius crickets on mostly barren lava on Hawaii Island. We used live traps baited with shrimp paste. Sampling sites were distributed among three regions:  C. anahulu was present in Kona, C. fori was present in HVNP, and C. fori was expected to be present in Puna.   

Trap histories for Caconemobius on the Big Island of Hawai’i, 2019.  Data accompanies Heinen-Kay et al. (2021) Ecological Entomology, which details the sampling design.  Each line represents a single trap that was open for 1 to 5 nights, beginning on the date given.  “1” represents a trap-night on which a Caconemobius was captured, “0” a trap-night on which one was not.  Sampling sites were distributed among three regions:  C. anahulu was present in Kona, C. fori was present in HVNP, and C. fori was expected to be present in Puna.