Reinterpreting an Eocene amber tiger beetle

Reinterpreting an Eocene amber tiger beetle

Tetracha carolina from the Essig Museum collection.

There are about 3,000 species of tiger beetles (Cicindelidae) worldwide, many of which are in decline, and several listed as endangered or threatened. Known for their speed, predatory prowess, and beauty, they are a popular group among hobbyists and an active area for research.

There are only a few known tiger beetle fossils, but one of the most cited is the extant tiger beetle Tetracha carolina (Linneus, 1763) that was identified by Walther Horn over a century ago (Deutsche Entomologische Zeitschrift, 1906: 329–336). UC Berkeley Professor Kipling Will, who recently re-studied this amber fossil, provides some insight as to why this identification prompted further questioning: 

“There was this standing idea that a species of tiger beetle had persisted as a species level taxon for 30 or 40 million years without change. If you followed what Horn originally said, that this was Tetracha carolina, then you’d have to assume that there’s really been no significant evolution of this species over that long period of time which seems a little odd. We expect species turnover differences to happen at a much quicker rate than that. And the Baltic is nowhere close to the current distribution.”

Current distribution of Tetracha spp. (green shading) and location of amber fossil (green circle). From Schmidt, J., Scholz, S., Wiesner, & Will K. 2023. “MicroCT data provide evidence correcting the previous misidentification of an Eocene amber beetle (Coleoptera, Cicindelidae) as an extant species.” Scientific Reports 13, 14743.

Amber fossils can be difficult to analyze due to the natural visual obstructions, such as patina flow lines, dust particles, air bubbles, and corrosion cracks. Using standard optical microscopes, researchers are also limited in what traits can be used for identification, because they can only see what is visible to the eye. However, with recent technological advances, such as MicroCT scanning and 3D imaging, detailed and interactive models of fossil specimens can be recreated.  Because of this technology the team was able to challenge Horn’s identification.

Recording of the fossil specimen’s 3D model.

“With the MicroCT scanning, we can see through all of that, and then produce these images. Even though that fossil was never in my hand, I could see all of the images and I could study all the details. And once we publish it, if people in the future disagree with us, well, they have the exact same things to look at as we did.”

Will and colleagues discovered that Horn’s fossil was not an extant Tetracha, but an extinct Palaeoiresina cassolai.

“Both the age and the distribution make sense. If there are examples of things that persist unchanged for 30 or 40 million years, this is certainly not one of them. And we think that’s unlikely for pretty much any of the fossils of that age.”

Identifying fossils is important because of how other researchers will integrate the fossil data into their own work.

“We can build phylogenies and that tells us about relationships, and we can talk about relative divergence from an ancestor to all descendants. But those phylogenies are not time-calibrated. We want to look at things like diversification rates, the timing of evolution of novelties, and all the kinds of fun stuff in the context of everything else that’s happening on the planet. Like, what were the positions of tectonic plates? What was the climate like 30 million, 50 million, 100 million years ago? Correlating phylogeny and the forces that drove evolution and extinction. So having the fossils carefully studied allows us to calibrate those trees and then lets us look at that story through time. Understanding the events of the past will help us make more accurate models of the future.”

Professor Kip Will examining the model.

Story by:
Sloane Sim, Media Specialist
Essig Museum of Entomology

Monitoring Biodiversity in Post-Fire Santa Cruz Mountains

In August of 2020, a fire that began as a smoldering lightning strike, erupted into a firestorm that roared across the Santa Cruz Mountains, scorching over 86,000 acres of forest and surrounding communities. The CZU Lightning Complex Fire burned for over a month before being fully contained and was the most destructive fire to ravage Santa Cruz County in over a century.1

Today, as part of the Sponsored Projects for Undergraduate Research (SPUR) program, students from Professor Kip Will’s lab are helping to monitor the effects of post-fire removal of trees and underbrush at various intensities on the diversity and abundance of terrestrial arthropods, especially ground beetles (Carabidae). The project is part of a larger study being conducted by Professor Scott Stephen’s lab in ESPM, and in cooperation with the Amah Mutsun Land Trust Stewards, the Bonny Doon Fire Safe Council and the California Department of Forestry and Fire Protection (CalFire). The study area is located in San Vicente Redwoods Preserve in the Santa Cruz Mountains – a mixed hardwood forest dominated by oaks, douglas fir, madrone and bay trees – that burned in the 2020 CZU Lightning Complex Fire. 

Each pitfall trap is set with a cover to prevent rain from getting in

In an area of moderate intensity burn where the forest canopy remained intact following the CZU Complex Fire, students help to set up pitfall trap arrays and temperature and humidity data loggers in nine plots, each in one of three forest fuel and selective tree removal treatments.  The three treatment types are categorized as minimal, moderate, and intensive levels of cutting and removal of trees and underbrush. In addition, one round of spring and fall sampling across all nine plots was done prior to the treatments to act as a baseline control sample. 

Retrieving specimens from the traps

A total of 72 pitfall traps are set in the nine transects two times per year – once in spring and once in late fall. Each pitfall trap is left for a one-month period after which time the samples are collected into Whirl-Pak bags and brought back to the lab. At the same time, temporal and spatial data collected from the field are entered into the Essig Museum’s online database.

Digging to set the traps and retrieval of samples is dirty and physically challenging work, often on slopes where poison oak is abundant. In the process, students learn valuable field techniques including how to set up sampling regimes and record accurate environmental data. Back in the lab students also learn how to sort trap samples and identify arthropods. The project will yield thousands of specimens including hundreds of species over the three-year survey period.

Sorting specimens from the trap samples

The data collected from this ongoing project will provide opportunities to study how different post-forest fire fuel treatments affect not only the diversity and abundance of ground-dwelling arthropods, but how overall forest health, structure and resources recover following fuel reduction and subsequent prescribed burning in San Vicente Redwoods Preserve.

The value of data collected from long-term monitoring projects like this will long outlive the project itself. Locality data and identifications recorded in the Essig Museum’s online database and the specimens in the museum’s collections provide an important resource for current research as well as future research and education. These vital resources can help inform not only our understanding of current species distribution patterns but also help answer questions about the effect of future landscape and climate changes. – Roberta Brett

  1. 2022-5_CZUFire_Report.pdf

Sulawesi Expedition

The island of Sulawesi (aka. Celebes) is nestled between Borneo, Papua, and the Philippines in a region of Indonesia known as Wallacea. It was formed by a collision of the Asia plate, Australian plate, and a system of island arcs, each contributing their fauna and flora. The resulting complex biogeographical patterns were a fascination to Alfred Russel Wallace and continue to be for modern biologists. Thanks to an NSF Biodiversity: Discovery & Analysis grant (DEB 1457845) led by Jim McGuire of the Museum of Vertebrate Zoology (MVZ), and co-PIs Rauri Bowie (MVZ), Rosemary Gillespie (Essig), and Susan Perkins (AMNH), a multi-taxon team of biologists will survey an elevation gradient across nine volcanoes distributed throughout the island.

The first expedition in July-August 2016 was to Latimojong in the northern part of South Sulawesi. Six researchers from the Berkeley Natural History Museums: Peter Oboyski (Essig), Jim McGuire, Rauri Bowie, Luke Bloch, Alexander Stubbs, Jeff Frederick (MVZ),  along with Heidi Rockney (SF State) met with colleagues from Australia and the Indonesia Research Center for Biology in Bogor, West Java to organize the inaugural trip. Permitting and other paperwork took two weeks onsite, and this was the expedited processing! Fortunately we were able to visit the Museum Zoologicum Bogoriensis and the Bogor Botanical Garden, and buy field supplies while we waited. The entomology collection is extensive with butterflies and other macrolepidoptera, beetles, bugs, bees, and flies well represented. Not so well represented are microlepidoptera and spiders – two of the targets of this expedition. The facilities are modern with good climate control. The well-educated and knowledgeable curators and staff prepare and database accessions, conduct research, and train students. Although there were some language barriers, there were enough people from each team that spoke the others’ language, which greatly facilitated our collaboration.

Two weeks later, over 20 biologists flew from Jakarta (Java) to Makassar (Sulawesi) to purchase final supplies and make the ten hour drive to the town of Belopa where we spent the night. The next morning we made our final push, by 4WD vehicles to the village of Gamaru – our first field camp. The village, at 1350m elevation, included ~20 simple wooden houses within a matrix of coffee plantations, small gardens, ponds, and secondary native forest. Our home for the first few days was the house of one of the village leaders, while a team of local villagers begin building our field camp and porting gear and supplies.

The first week was rainy and muddy, but the new moon was optimal for UV light collecting. On the first night, a sheet hung under the house with a view into the valley below was one of the best nights of moth collecting.

The next camp was at 1730m along a trail leading from Gamaru village. More secondary forest with a lot of invasive plant species along the trail, but native forest off the trail. We set up pitfall traps, malaise tents, and sifted leaf litter to put in winkler funnels at 100m intervals from 1800 to 2400m, but did not acquire many specimens (possibly due to rain or poor timing). Hand collecting for spiders proved very productive. The highest field camp (2800m) was in a dwarf forest / bog along the upper ridge of the mountain – a distinctly different habitat with a unique insect fauna.

The last few days of the three-week field operation was spent in another village at 800m, which was in the process of being cleared for agriculture and development. Remnants of native forest remained and collecting was generally good. But it was clear that this area would soon be completely converted to agriculture, like many rural areas. After returning to Bogor and the museum, it was time to count specimens for export permits and pack our bags.


  • by Peter Oboyski