A TALE OF TWO TESTACEUS
Location: Southern CA, Mountain foothills near desert
Date: April 3rd, 2021
Habitat: Mountain desert
Elevation: ~4000ft
Length: 12-13mm
Coloration: Dark brown body, yellow legs
Distinguishing characteristics: Very hairy, look like very large M. testaceus
Nest description: assymetrical mounds, 8-12 inches, workers are strictly nocturnal and come out at the last light of sunset
Been anting at this spot for years. It's the closest region with Myrmecocystus to where I live, but this is the first time I have found these.
In the past I had always noticed these large yellow workers at night which I assumed were Myrmecocystus mexicanus, but had never found M. mexicanus queens here. A few years ago found M. testaceus and M. wheeleri dealates in the same spot, which made me question what these large yellow workers were. You usually don't find M. testaceus (generally a mountain species) in the same habitat as M. mexicanus (generally a desert species).
This past week I stumbled on these large Myrmecocystus queens that looked like giant M. testaceus, and assumed that may be what they were. Keyed them out, and the closest they come to is Myrmecocystus mexicanus (in the Myrmecocystus subgenera in the Mexicanus group). I wasn't even looking for queens, but was hiking. Weather was cold, hi 70s and low 47.
I also gathered large major workers from the nests as well. Both queen and workers have 9 rows of teeth. Testaceus have 8, Mexicanus group have 9. Queen and workers have head width at around 2mm. M. testaceus head width do not exceed 1.85mm.
The queens, however, look nothing like M. mexicanus, and in fact look more like a large off colored M. testaceus.
The workers heads also do not resemble M. mexicanus. They are "orbiculate", as Snelling would describe M. placodops. I've included head shots of both M. mexicanus and these workers below.
At this point I have no idea what these are, and it could be undescribed. This is the only area I have found these queens. I plan on sending specimens to Brian Fisher to have them genetically sequenced.
This is a 20mm test tube to give you a sense of size of this queen.
Queen has 9 rows of teeth as do the major workers.
For comparison, here is an M. testaceus queen found in the exact same region in a 20mm wide test tube.
M. mexicanus major worker head
Unidentified major worker head, more "orbiculate"
Edited by nurbs, April 26 2023 - 9:01 PM.
