Here’s one of my favorite Arizona insects. Laccophilus pictus is a small diving beetle, less than a centimeter long, that is common in small ponds and streams in the mountains south of Tucson. It’s also one of the beetles that we’re using as an exemplar taxon for the Beetle Tree of Life project. Very pretty, no?
Ground beetles- the family Carabidae- are a spectacular evolutionary radiation of terrestrial predators. The elegant, flightless beetles of the genus Scaphinotus prefer snails and slugs.
So you like insects, but can’t be bothered to get up from your computer to go look for some? Google earth to the rescue!
South of Tucson, Arizona (31°38.097’N 111°03.797’W) I found this lovely aerial image. Visualized from an elevation of about a kilometer and a half, it shows a hill just west of I-19 covered in freshly-sprouted grass. Except, there’s this strange pattern of evenly-spaced polka-dots:
What could account for the speckles? Alien crop-circles? Bizarre gardening accidents?
Why no, those are the nest discs of one of our most conspicuous insects in the Sonoran desert, the red harvester ant Pogonomyrmex barbatus. Down on the ground it is harder to get a sense of the even spacing of the nests, but the discs are plenty obvious. The ants keep the large area around their nest entrance free of vegetation and other unwanted debris. Below is a photo I took south of the Huachuca mountains, not far from the google earth image above:
Even closer-up, here are the engineers:
North American Pogonomyrmex aren’t the only ants whose engineering prowess is visible from low-earth orbit. Some of the more spectacular leafcutter ants in South America make even larger mounds. The image below the fold is also from Google Earth, 1 km over the Paraguayan Chaco (24°06.914’S 57°22.240’W).
“I went out collecting with Albert Way of Trinity, who in after years became a well-known archaeologist; also with H. Thompson, afterwards a leading agriculturalist, chairman of a great railway, and a Member of Parliament. It seems therefore that a taste for collecting beetles is some indication of future success in life.”
– Charles Darwin
f/20, 1/2 sec, ISO 400
camera on tripod, natural light
levels adjusted in Photoshop
New species discovery is not so simple as finding a critter in the woods and declaring “Eureka!” A background knowledge of related species is essential for recognizing something novel. Trachymyrmex has been an especially challenging group of ants in this regard, as the published taxonomy of the group is limited and many of the species are confusingly similar. In the absence of a taxonomic synthesis, one is reduced to using isolated taxonomic papers written decades ago on individual species and going through endless drawers of museum specimens. Fortunately, Rabeling et al. do exactly that for the North American Trachymyrmex, and on top of it they throw in DNA sequence data from two loci sampled across multiple populations per species. Once the dust settled, they inferred the existence of nine species but had only eight valid, pre-existing names to apply to them. The extra species became the new T. pomonae.
Students of the biannual Ant Course in Arizona might recognize T. pomonae. It is not an uncommon ant around the Southwestern Research Station in Portal where the course is taught. If you’re an Arizona Ant Course alumnus, check your collection!
Colliuris sp. long-necked ground beetle, Arizona
details: Canon MP-E 65mm 1-5x macro lens on a Canon 20D
beetle on plain white paper
f/13, 1/250 sec, ISO 100
MT-24EX twin flash diffused through tracing paper
levels adjusted in Photoshop