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.

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.

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.

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.

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

We also came across an Eleodes, probably E. 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.

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.

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.

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

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.

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.

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.

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.

There were also quite a few springtails (Collembolans), probably of several species.

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.

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.

One weevil fell into a trap. It is about 6 mm from nose to tail. Looks somewhat like Ophryastes, but I am not certain.

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.

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.

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

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

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.