Last fall, we gathered data on the physiology, temperature sensitivity and lifespans of Eleodes obscura and its presumed mimic Philolithus elatus. The data were interesting and I have drafted a paper, but it seemed worth trying to replicate the results to be sure the data were solid.
One of the limitations of working with a seasonal organism, like P. elatus, is that one can only work during a narrow window, when the animals are available and alive. True stink beetles, like E. obscura, survive for years, so one can simply collect a bunch and then do experiments almost indefinitely. Philolithus die less than two months after emerging, then are completely gone until late the next summer.
Hence my excitement at finding the first P. elatus of the season.
The first Philolithus elatus collected in 2025. 7/27/25.
More are emerging every day. We now have seven P. elatus available for experiments, and are hoping to bring the total to twenty within the next week. There are plenty of E. obscura available as well. We should soon have a big pile of data to add to the manuscript.
For a little more info on P. elatus, check out the new Wikipedia page that I started.
The islands in the Gulf of California provide a natural laboratory for the effects of “spatial subsidy,” the movement of resources from a rich environment (the sea) to a more impoverished habitat (the desert islands). In this context, scientists have studied many species on the islands, including Tenebrionid beetles. The abundance and diversity of beetles on the islands of Bahia de los Angeles have been surveyed for at least 30 years, and my good friend and colleague Dr Drew Talley has been leading the studies for most of that time. In recent years, Dr Natalia Rodriguez Revelo, an expert in beetles and dune ecology, has participated in the work with Drew. I have participated in various roles for several of the past 20 field seasons, and was once again privileged to spend time with them and help out on the islands this year.
Drew and Natalia counting beetles on La Ventana. 6/28/25.
The procedure is straightforward in principle: on each island, set multiple pitfall traps (plastic party cups) baited with lean pieces of fish. The beetles (and, occasionally, other creatures) fall into the traps. Six days later, the traps are checked and the number and species of beetles are scored. In practice, mice or gulls can steal bait if it is not adequately secured, or fat from fish guts can turn the contents of the cup to smelly soup.
In a perfect world, traps would be set on all of the accessible islands in the bay. In practice, time constraints forced us to prioritize. This year, we sampled Coronadito, Coronado (also known as Isla Smith), Flecha, Pata, Llave, Cerraja, La Ventana, Cabeza de Caballo, and Gemelos West.
I made an effort this year to photograph each species using a platform with tacky wax to secure the beetle, and a scale to document its size.
Map of the bay at Bahia de los Angeles. Most islands, including all islands sampled this year, are labeled. The town of Bahia de los Angeles is labeled at lower left.
It was marginally successful, and provided insight about how to improve future versions.
Below is a draft guide to the beetles found on the islands, When possible, photos are provided of beetles held in fingers and mounted on the photography platform. Cartoons provide graphic representation of the relative sizes of the beetles, ranging from tiny (Batuliodes) to hefty (Cryptoglossa), keeping in mind that the sizes of all species can vary significantly.
Distribution of each species are based on data from Sanchez Piñero and Aalbu (2002). A table extracted from their observations can be found here.
Click the photographs if you want to see larger versions.
Argoporis apicalis
Medium sized, with ridged elytra and reddish legs. Argoporis is one of the few Tenebrionids on the islands which possess defensive glands in their abdomens.
Found on all islands except Mitlan (tiny island next to Coronado).
12 mm
Argoporis apicalis trapped on Coronadito island. 6/26/25.
Argoporis apicalis trapped on Cerraja island. The blurred image of an extra antenna was caused by using focus stacking to improve depth of field. 6/27/25.
Batuliodes confluens
This tiny brown beetle with roughened pronotum and elytra.
Found on the majority of islands, and may be undercounted due to its small size.
~3 mm
Batuliodes confluens trapped on Flecha island. 6/23/14
Batuliodes confluens trapped on Cerraja island. 6/27/25.
Cryptadius tarsalis
Small, oval, and deep-bodied, with dense rows of small punctures on the elytra.
Cryptadius is found on Bota, Cerraja, Coronado, Jorobado, Mitlan and Pata.
8 mm
Cryptadius tarsalis.trapped on Llave island. Scale bar, 2 mm. 6/27/25
Cryptoglossa spiculifera
One of the largest beetles on the islands, with elytra decorated with rows of raised, spiny bumps.
Found on the largest islands (Coronado, Cabeza de Caballo, but not La Ventana) as well as the rookery island, Gemelos West.
28 mm
Cryptoglossa spiculifera trapped on Gemelos West island, 6/28/25.
Cryptoglossa spiculifera trapped on Gemelos West island. Scale bar, 10 mm. 6/28/25.
Microschatia championi
Slightly smaller than Cryptoglossa, the elytra of Micoschatia are decorated with dimples rather than sharp bumps and there are punctures on the lateral pronotum of M. championi.
Present on all but the smallest islands.
20 mm
Microschatia championi trapped on Cerraja island. 6/27/25.
Microschatia championi trapped on Cerraja island. Scale bar, 5 mm. 6/27/25.
Stibia sparsa
Shaped like a typical Tenebrionid, with dense punctures on the pronotum and rows of punctures on the elytra.
Stibia can be found on the largest islands (Cabeza de Caballo, Coronado, La Ventana) plus Gemelos West.
11 mm
Stibia sparsa trapped on Gemelos West island. 6/28/25
Stibia sparsa trapped on Gemelos West island. Scale bar, 2 mm. 6/28/25.
Tonibius sulcatus
Very small and reddish, with relatively smooth pronotum and strongly ridged elytra.
Described from most islands, except Coronaditio, Gemelos West, Jorobado and Llave.
6 mm
Tonibius sulcatus found at Las Hamacas hotel. 7/10/24.
Triphalopsis californicus
Small, black, oval, and deep-bodied. Covered with fine hairs that are often coated in dust.
Triphalopsis has been described from all islands except Gemelo West.
8 mm
Triphalopsis californicus trapped on Flecha island. 6/27/25.
Triphalopsis californicus trapped on Cerraja island. Scale bar, 2 mm. 6/27/25.
There are many other beetles, including various species of Histeridae and Dermestidae (not shown).
Hister Beetle on Coronadito Island. Scale 2 mm. 6/26/25.
Centipedes, spiders, and scorpions are often found in the traps in the larger islands.
Scorpion trapped on La Ventana. 6/28/25
References
Sanchez Piñero, F. and Aalbu, R. L. (2002). Tenebrionid Beetles (Appendix 6.1). In A New Island Biogeography of the Sea of Cortés, pp. 129–153. New York: Oxford University Press.
A little bit of physiology to start off the summer.
We are gearing up to complete the data sets for local beetles this fall. Ultimately, we’ll be comparing metabolism of two Eleodes species, E. obscura and E. longicollis, with those of a few mimics, Philolithus elatusand Stenomorpha marginata. The data from last fall were very interesting, but after drafting the manuscript it was clear that another season of data would help to clarify the results.
Because of seasonal availability, comparing Eleodes with their mimics will have to wait until late summer and early fall. Eleodes longicollis is common all summer, but E. obscura becomes much more common in July. Philolithus elatus and S. marginatus will not appear until the end of July at the earliest.
In the meantime, there were a couple of other species available in the lab that will help in understanding the data from Eleodes, Philolithus, and Stenomorpha.
Zophobas morio. Yellow paint on right elytra is for individual identification.
Zophobas morio, also known as the “superworm,” is originally from the American tropics. It is widely cultured as a food for pets and is being considered as a source of protein for humans. A colony was established in the lab in early 2024, so they are available for experiments any time. Being from the neotropics, with consistently warm and relatively wet conditions, they are expected to respond more strongly to temperature changes.
Asbolus verrucosus, the blue death-feigning beetle.
Asbolus verrucosus, called the blue death-feigning beetle because of its tendency to play dead when handled, is a long-lived species from the hot, dry deserts of southwestern North America. We received a cohort from Bugs in Cyberspace in January, and they have spent the past few months adjusting to handling and conditions in the lab. Their adaptations to extreme conditions suggest that they will be tolerant of high temperatures.
Oxygen consumption was measured for the two species from 15°C, at which beetles should be slow and sluggish, to 40°C, just below the lethal temperature for a close relative of A. verrucosus (Cryptoglossa muricata; Ahearn, 1970). Therefore the temperature range may cause cold stress at at the low end and heat stress on the high end, but was not expected to be lethal.
The two species are just about the same size and mass, with each being somewhat over half a gram. Twelve beetles of each species were tested at each temperature, although technical issues reduced this to eleven in a few cases. The respirometer could handle eight beetles at a time, so four of each species were tested together each day, and each temperature required three days of experiments.
Oxygen consumption of Z. morio and A. verrucosus between 15°C and 40°C. Each point shows the mean and standard error of 11-12 beetles, with most error bars smaller than the symbols. At each temperature above 15°C, Z. morio consumed more O2 than A. verrucosus. At 40°C, all Z. morio were visibly impaired immediately after experiments, and 8/12 were dead within two days. None of the 12 A. verrucosus showed any signs of stress after 40C experiments, and all survived indefinitely (one week so far) after being returned to their enclosure.
At 15°C, O2 consumption was identical for the two species. At every other temperature, Z. morio consumed significantly more O2 than A verrucosus. This may reflect a lower standard metabolic rate for the desert species, which is adapted to an environment with limited resources. Neither species showed any sign of stress at either 25°C or 35°C, in that both emerged from experiments active and coordinated, and none died in the three days between experiments.
The two species diverged further at 40°C, with Z. morio dramatically increasing their O2 consumption (note the log10 scale), while O2 consumption in A. verrucosus increased only slightly. Importantly, all Z. morio were visibly impaired at the end of 40°C experiments, showing slow, uncoordinated movement or no movement at all. Eight of twelve Z. morio were dead within two days. In contrast, none of the A. verrucosus tested at 40°C appeared to be stressed, and all survived indefinitely.
It is perhaps not surprising that Z. morio, a species originating from a relatively constant, resource rich environment, has a higher metabolic rate and is more sensitive to environmental temperature than the desert beetle, A. verrucosus. The dramatic increase in O2 consumption and lethality between 35°C and 40°C for Z. morio was quite striking, however. The lethality-associated increase in metabolic rate resembles that in the fruit fly, Drosphila melanogaster at 35°C (Sandstrom et al., unpublished), and indicates that a dramatic increase in O2 consumption may be a common indicator of severe heat stress in insects.
There are a few possible caveats. For example, although the two species have been kept under the same conditions for at least four months, which should be enough to reduce the effects of previous physiological adaptations, their life histories as larvae and pupae were different. Z. morio have been reared for multiple generations at the lab, while A. verrucosus were collected from the wild, which may somehow influence their responses to temperature. Asbolus and their relatives can be reared in captivity (Rider, 2024), so it may be worth repeating the experiment with lab-reared beetles.
References
Ahearn, G. A. (1970a). Changes in hemolymph properties accompanying heat death in the desert tenebrionid beetle Centrioptera muricata. Comparative Biochemistry and Physiology33, 845–857.
Rider, S (2024) Death Feigning Beetles of the United States and Mexico. Publisher S. Rider Jr. 182 pp.
In addition to its other functions, this site serves as a notebook for keeping track of data and references. In our effort to keep a handle on the local species’ characteristics and publications, information about each will be posted on its own page.
Eleodes obscura, participating in notetaking. 9/20/23.
The first species to receive this honor is the prominent, large, and widespread stink beetle, Eleodes obscura. It has been the subject of field surveys, respirometry experiments, and longevity studies here at the lab, and may be the most studied species of Eleodes.
Expect more pages to become active with time. Hopefully, this will become a resource that many people in the community can make use of.
Pitfall trap array after a night of snowfall. The blue flags marking the locations are visible, but the traps are difficult to find. 3/8/25.
The pitfall traps were set this month with the expectation that it would be too cold for small arthropods to be active. The data would serve as a baseline for later surveys, when bugs would be more active. As if to emphasize this point, we got a few inches of snow the night before the traps were to be collected.
Pitfall trap under snow. It is somewhere near the flag. 3/8/25.
Even though each trap was marked with a flag and had a big rock on top, some were hard to find under the snow, and I had to be careful to avoid spilling too much snow into the cups.
When I got them back to the lab, I was in for a surprise.
Ant caught in pitfall trap. Species unknown, but not Pogonomyrmex. 3/8/25.
The cups were not overflowing with life, but there was plenty to see. The most common insects were ants. About half (maybe 5) were the large, leggy species shown above. The rest were the much smaller species shown below. Sorry there’s no scale, but they were moving too quickly for that. I preserved some, so may post better photos later.
Small ant species. 3/8/25.
There were also quite a few springtails (Collembolans), probably of several species.
Springtail caught in pitfall trap. 3/8/25.
They are extremely tiny, and I know little about them, so all I can say at this point is that there were springtails active in the neighborhood.
Spider from pitfall trap. 3/8/25.
There were also at least three spiders, of at least two species. According to iNaturalist, the spider shown above is a ground crab spider in the genus Xysticus.
Most exciting were two species of beetles.
Grey weevil with dark blotches, covered with coarse hair. 3/8/25.
One weevil fell into a trap. It is about 6 mm from nose to tail. Looks somewhat like Ophryastes, but I am not certain.
Beetle larva, probably in the family Melyridae. Note the relatively long thorax and the urogomphi (spiky things) extending from the end of the abdomen. Ruler scale is millimeters. 3/8/25.
There were also two larvae that looked like they were in the family Melyridae, or soft-winged flower beetles. They looked identical to each other, so maybe they are relatively common around here. The larval biology of most beetles, including the Melyridae, is not well documented, so it may be impossible to determine the species of these guys.
It was a pleasant surprise to find some little arthropods in the traps this month, especially a few species of beetles.
There were, however, no Tenebrionids as yet. In that way, this month’s collection does actually serve as a control. I expect that we may find some of them when the traps are reset in early April.
I got a shipment of 15 blue death-feigning beetles (Asbolus verrucosus) yesterday from Bugs in Cyberspace. If the goal of the lab is to study the biology of the local wildlife of the semi-arid savannah, why would I be interested in Asbolus, a creature from the hot, dry Sonoran and Mojave deserts? Well, aside from them being cute, lumpy, blueish, and acting like they are dead (see below), their biology is worth a look. Compared to the local species of Eleodes and Philolithus, Asbolus is adapted to much more extreme conditions, with scarce resources and high temperatures. One reported adaptation for these difficult conditions is a much lower metabolic rate than those I have measured for Eleodes and Philolithus. However, the experiments were done long ago and under different conditions. When I saw that these guys were available online, it seemed like an excellent opportunity to revisit their oxygen consumption and temperature sensitivity.
Tenebrionid beetles, like Eleodes, Philolithus, and Asbolus, employ thanatosis, or playing dead, as a defensive strategy. With Eleodes and Philolithus, I am accustomed to them freezing for a while during handling, but it is not particularly convincing. Most of the time they try to wiggle away rather than playing dead.
Don’t eat me, I’m dead.
Asbolus, on the other hand, lives up to its name of death-feigning beetle, and fakes its own death at every opportunity. Whenever they are handled, they turn over and stick their legs out like cartoon characters, and will do so repeatedly. This may be their only choice. They have no defensive stink glands (like Eleodes), nor do they mimic a stinky species (as Philolithus mimics Eleodes), so playing dead may be the most effective strategy.
They will need to settle in for a few weeks before experiments get started, and the real test will be in the summer when all of the local beetles have their metabolisms at full throttle.
