Tierra de Oro Laboratory

Physiology and Ecology in the Pinyon-Juniper Savanna

Category: fieldwork

Mimicking Stinky Beetles: How good is good enough?

Many of the darkling beetles here are members of model/mimic complexes. Specifically, some species of Eleodes, which can defend themselves chemically by using scent glands in their abdomens, serve as models for members of other genera, such as Philolithus and Stenomorpha, which do not have glands (Brown, 1971; Smith et al., 2015). In theory, the mimics are protected from predators by resembling the defended beetles, but save energy by not having to grow, maintain, and fill the glands. When a mimic resembles a defended species but does not have its own defense, it is referred to as Batesian mimicry.

As we look over the data from the past few seasons, it is worth considering some of the assumptions regarding models and mimics.

Advertising Bad Taste

Let’s start with the models, the chemically-defended Eleodes. If a species is noxious in some way, advertising this fact benefits both the prey and predator. If the predator knows that the prey is inedible, then the prey will avoid being eaten, and the predator avoids a mouthful of something nasty. Many noxious prey have bright, contrasting colors to make it easier to recognize them.

There are about six species of Eleodes commonly found here, and all have similar appearance and behavior. They are black, generally shiny, about 15 to 30 mm long (depending on the species), with variations in their body shapes and the patterning of the thorax and elytra (for an overview, see the local beetles page).

Eleodes obscura traveling across an open field. 7/9/25.

One could argue that uniformly black beetles are not very striking, and may therefore be doing a poor job of advertising their distastefulness. However, when walking about, they put little effort into concealing themselves, and a shiny black beetle is pretty easy to see on a background composed of shades of brown and drab green. Further, when approached the beetles stand on their heads to aim (and presumably show off) their scent glands.

Eleodes obscura reacting to an approaching threat by standing on its head. 8/17/24

These guys may not be as flamboyant as a coral snake or a lionfish, but they get the point across. After a few tries, a predator will probably get the idea that attacking one of these beetles will result in a face full of noxious chemicals.

The Mimics

From April to late July, the area is inhabited mostly by “honest” beetles, whose appearance and behavior truly reflect their ability to defend themselves. Starting in late summer/early fall, a group of “cheaters,” or mimics, starts to emerge. These are beetles that are about the same size and appearance as Eleodes, and in some cases act like them, but do not have defensive glands.

Eleodes obscura dispersa and Philolithus elatus infernus at the same scale. The elytra show similar patterns of ridges and punctures. Paint spots mark them for physiological studies.

One species, Philolithus elatus, is considered to be an accurate mimic of E. obscura. Both E. obscura and P. elatus have multiple geographic subspecies, and the patterning on the elytra of each P. elatus subspecies resembles that of the E. obscura subspecies that shares its range (Brown, 1971). In the example above, the elytra of P. elatus infernus found in Santa Fe have weakly defined ridges, similar to those of the local E. obscura dispersa.

Philolithus emerges in late July and is abundant through August and early September. This means that predators have had since the beginning of April to sample Eleodes and learn that shiny black beetles taste bad. Another supposed mimic of E. obscura, Stenomorpha marginata, emerges even later, in late August and is present in September and October.

Stenomorpha marginata. 9/3/25.

At first glance, the mimics could easily be mistaken for E. obscura, and a predator might pass them by. At other loacations, it is reported that both species even mimic the headstanding behavior of Eleodes (Brown, 1971; Smith et al, 2015). Here in Santa Fe, it takes physical contact (rather than a close approach) to get P. elatus to respond, and even that is half-hearted.

Philolithus elatus giving its best effort at a headstand.

Stenomorpha marginata bracing for whatever comes next. 10/1/25.

Stenomorpha does not even bother with a lame attempt, and just extends its legs outward to brace itself when touched.

Another mimic produces more convincing headstands. Moneilema appressum, the cactus longhorn beetle, is a member of a completely separate family of beetles (Cerambycidae). Nonetheless, its smooth, shiny appearance and willingness to stand on its head when approached make it a convincing mimic of Eleodes longicollis.

Eleodes longicollis raising its abdomen in response to an approaching experimenter.

Moneilema appressum performing a convincing headstand. 8/20/25.

All of this leaves a few open questions.

First, how good does mimicry really have to be? From April to August, just about every shiny black beetle that a predator encounters is chemically defended. Do Philolithus and Stenomorpha need to imitate the appearance and behavior of Eleodes all that precisely, or is it enough to be a shiny black beetle of about the right size and shape? Based on scat found around here, someone is definitely eating Eleodes, so it’s likely that some mimics will get eaten anyway.

The fact that Moneilema seems to do a better job of looking and acting like an Eleodes species is intriguing, although I am not sure what to conclude at the moment.

Philolithus elatus regurgitating in response to handling. 8/11/25.

Second, are the mimics truly undefended? Philolithus will regurgitate when handled roughly, which, at least for grasshoppers, qualifies as chemical defense. Further, they feed, oviposit, and their larvae probably live among harvester ants (Pogonomyrmex sp.) during their development (McIntyre, 1999; Slobodkovich, 1979). It seems plausible that the beetles acquire some sort of chemical signature from the ants that deters attacks by the ants and other predators.

Stenomorpha, on the other hand, appears completely undefended. I have not observed them to regurgitate, they do not appear to associate with ants, and they do not have scent glands. They may be less vulnerable because they emerge so late in the season, but we will need to know more about their predators to have any insight into this.

References

Brown, K. W. (1971). A population approach to computer taxonomy with applications in the genus Gonasida.

McIntyre, N. E. (1999). Use of Pogonomyrmex nest-sites by Tenebrionid beetles (Coleoptera: Tenebrionidae) for oviposition and thermoregulation in a temperate grassland. The Southwestern Naturalist 44, 379–382.

Slobodchikoff, C. N. (1979). Utilization of Harvester Ant Debris by Tenebrionid Beetles. Environmental Entomology 8, 770–772.

Smith, A. D., Wilson, J. S. and Cognato, A. I. (2015). The evolution of Batesian mimicry within the North American Asidini (Coleoptera: Tenebrionidae). Cladistics 31, 441–454.

October 19, 2025
The Game’s Afoot!

Or underfoot, as may be.

Philolithus elatus have started to emerge

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.

August 5, 2025
Baja California: Annual Island Survey

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.

July 5, 2025
Spring Is Here: Turkeys, Beetles, and Owls

A little warmth brings out a lot of wildlife

In the past week, temperatures have shifted upward dramatically. It’s above freezing every night, and plants and animals have responded appropriately. There is so much to see.

We made a quick trip down to Bosque del Apache Wildlife Refuge near San Antonio, NM. The sandhill cranes are all gone, but there are plenty of ducks and songbirds. We stayed at a house near San Antonio, and were treated to a small group of wild turkeys. The females spent a lot of time foraging near the house, and a male would occasionally stop in and try to woo them.

Male turkey doing his fancy dance and looking just like a Thanksgiving centerpiece. 4/11/25. The download speed may not be quite enough for perfect streaming, so you may want to re-run it for a smoother experience.

There were also a few mammals, such as javelinas and coyotes.

Javelina at Bosque del Apache North Loop. 4/10/25.

We also came across an Eleodes, probably E. gracilis

Eleodes gracilis.

Back at the lab, spring is in full swing. Winter birds, like juncos and robins, have moved on, and summer residents, including lesser goldfinches and Say’s phoebes have settled in.

Some of the year-round residents, such as western bluebirds (and, of course, screech owls) are taking their jobs as parents seriously.

Male and female western bluebird staking out their new box. 3/15/25.

As added enticement, we replaced the old bluebird box with a shiny new one.

Stink beetles are very much making their presence known. One can now find multiple species of Eleodes on a casual stroll around the neighborhood.

Eleodes caudifera found wandering the street. 4/13/25

Eleodes hispilabris on trail near the lab.

Now that the weather has warmed up, this month’s pitfall trap survey was a bit more interesting.

There’s plenty of traffic through the field with the traps, including this big, fuzzy coyote that strolled through the week before the traps were set.

Coyote casually wandering through the field with the traps. The rock behind its right rear foot marks one of the trap sites. 4/2/25.

We caught a few Eleodes sponsa in the traps, along with wolf spiders, ants, and weevils.

Eleodes sponsa after a few measurements i n the lab. 4/12/25.

So the natural world has gone from quiet to extremely busy this month. Don’t forget to check out the updates on the owl cam page if you have a few minutes.

Female owl snacking on some leftover mouse. 4/10/25.

April 16, 2025
Life in the Frigid Wastes

Arthropods Active in the Cold

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.

March 9, 2025
Setting Up Pitfall Traps for Beetle Surveys in 2025

Starting surveys for 2025

Trap location, looking northeast. Small blue flags remain in place to mark locations of traps. One trap, with a painted cover held down by a rock, can be seen in front of the cholla cactus. 3/3/25.

Inspired by comments from my friend and colleague Dr. Drew Talley, and conversations with a local Master Gardener, we set up a small array of pitfall traps to collect and record beetles over the course of the year.

It is a 3 X 3 grid, so nine traps total, spaced 3 meters apart. We set out flags to mark the locations of the traps in a section of the back acre of the lab where foot traffic was minimal.

Pitfall trap, consisting of a plastic cup buried to the rim . Note that the rim is flush with the soil. 3/4/25.

The traps are plastic party cups, buried to the rim. The soil is quite loose, so placing the traps was easy.

Pitfall trap with plywood cover. Legs are partially buried, leaving space for entry of beetles. 3/4/25

Once the traps were in place, we put plywood covers over them to keep debris out and shield any animals that fall in.

Plywood covers for pitfall traps before painting. Covers are 6 X 6 pieces of plywood with 3/4 wooden dowels screwed into place.

The covers are 6″ X 6″ pieces of plywood, each with three legs made from 3/4″ dowels. The 3″ legs allow them to be partially buried for stability. Once screwed together they were given a few coats of latex paint to protect them from the elements.

We’ll set traps for the first week of each month, for five nights at a time.

I have not seen beetles in the neighborhood before April, so it is unlikely any will fall into the traps this month. Knowing when beetles are not active provides an important baseline for when they first appear.

March 4, 2025