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).

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.

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.

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.

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.

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.

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.

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.

Because it took so long to load when they were all on the same page, I have moved the owlet videos to new a series of pages. It’s slightly more hassle if you want to see all of them at one sitting, but it beats waiting what seems like forever for the pages to load. If you love it or hate it, use the contact link to send feedback.

More owl feedings. We are in the waiting period before the eggs hatch. The female sits on the eggs continuously except for short breaks. The male brings her mice and occasionally insects. Here are a couple clips of food deliveries. 

In the first one, you can get an idea of how long their legs are as she stands up to peer out the hole before he arrives with a kangaroo mouse

 In another clip, she is away when he pops in with a Jerusalem cricket (“potato bug”).

And a clip where she swallows most of a mouse that was leftovers. 

4/22/25: We Must Be Getting Close!

No owlet hatching yet, hopefully tonight to still meet my prediction.

In the meantime, here are two clips of mice deliveries: a kangaroo mouse and a field mouse from a few days earlier. 

The female has been spending all her time on the eggs and the last morning she has been fussing with them almost continuously and skipped her usual pre-dawn break. Maybe sensing the movement of the chicks inside?

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.

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 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.

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).

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.

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.

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.

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.

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.

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.

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.

There are many other beetles, including various species of Histeridae and Dermestidae (not shown).

Centipedes, spiders, and scorpions are often found in the traps in the larger islands.

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.

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 elatus and 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, 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, 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.

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 Physiology 33, 845–857.

Rider, S (2024) Death Feigning Beetles of the United States and Mexico. Publisher S. Rider Jr. 182 pp.

We have been very lucky to have a clear view of a pair of western bluebirds. There has been a nest box on the back lot for many years. Last fall, it was time to replace the old, battered box with a new one, and the birds settled in early this spring.

They were getting things ready by the beginning of March.

Despite the cold, they were ready to get started. Note the fluffed feathers in the photo above.

The process was largely mysterious, with the parents coming and going during April and May, but no sightings of the nestlings.

The babies finally started sticking their heads out in May. Mom and dad brought food on a regular basis/

By the last part of may, the kids were ready to see the world. Within a day of showing their heads, everyone was gone.

I cleaned out the old nest a few days after the fledglings left, and was surprised to see a pair of bluebirds bringing new materials less than a week later. It is impossible to say whether these are the same parents, but it seems likely. They can often raise more than one clutch per year, so maybe we’ll see more fledglings in a few months.

The parents have been out and about quite a bit, and seem unbothered by the presence of observers and paparazzi.

Family Album from Past Years

This seems like a good time to reminisce about past broods. It’s hard to know how long these particular parents have been rearing young in Terry’s box, but screech owls have been nesting there for many years. Terry has many more excellent photos; here is a small sampling.

The drama in the nest box continues. Based on past broods, he expects them to fledge on or about May 22. As always, stay tuned for more.

Below is one of his latest creations, which he has fine-tuned for scale and pacing. Enjoy!

I am certain that the beetles would be mesmerized by it if they had better eyesight.

At the moment, the owlets look like fuzzy blobs, but in the video you can see three sets of wiggly heads, bodies, and wings.

Let’s hope for the other two to hatch successfully in the next few days.