Download high resolution image here.
I collected this ant and mite on South Crest Trl (No. 130), 9400 ft,
Sandia Crest 7.5’ quadrangle in the
Sandia Mountains, Bernalillo Co, NM from a Berlese funnel loaded with soil from a 40 cm deep core sample taken of a
formica argentea ant nest. That is, the sample was from 0 to 40 cm deep in the nest. The nest was composed of a mound of loose soil about 150 cm diameter and rising about 20 cm high. I posted images of a representative worker ant from the nest, both sexes, and three immature stages (linked below).
This mite resembles
Antennophorus in appearance and behavior with notable exceptions. From Wheeler
(1),
Antennophorus clings exclusively to the bottom of the head of ants of the genus
Lasius, moving to the side or top only if the bottom is occupied by another mite. This host's genus is
Formica and, based on my observations of several attached mites, adults and nymphs alike cling to the side of the head exclusively (with no preference for left or right). I didn't observe any multiple attachments, though.
Antennophorus is reported to wave its front legs to mimic the host's palpi to obtain food from other ants. Ants solicit regurgitated food from others by waving their palps when hungry. This mite (which is very much alive initially) remained perfectly rigid for hours in the stance of the first two images. Also, the images I've found in Wheeler and on
BugGuide show that the subject has much longer and sparser setae on its dorsal shell than those
Antennophorus, at least. There are four
genera of Antennophoridae listed in TAMU's World catalogue
(2) other than
Antennophorus, each containing a single species. None are reported to parasitize
Formica as far as I can determine. This is either an undescribed genus, or
Formica must be recognized as a host to one
Antennophorus species. The sex determination is based on
ventral view comparison to images of male and female
Antennophorus genitalia in Wheeler.
Stacked imaging, the technique employed for all the images linked here, entails taking many pictures of an (ideally) static object with each at a slightly different distance from the lens (detailed below). The images here were taken 20 seconds apart and are linked in chronological order of taking. So, over 96 minutes elapsed for the first two, during which the mite remained motionless with its front leg extended along the side of the ant's mandibles. The ant is very nearly dead and motionless itself during this time. It was injured during core sampling by having its gaster crushed from the pressure applied to push and twist a steel tube through nest to take the sample. The mite started moving before any of it was in focus during the third sequence, as recorded by the individual fuzzy images, until it got to the configuration shown. The ant twitched its left antenna and front legs while the mite was in motion, presumably sensing and reacting to the mite's motion. They both stopped in time for a
final image construction to be possible. This
fourth image shows the stance the mite has in death. No longer clinging to the ant, it fell off when I removed the ant from the stage. It never moved again. It is likely that the mite succumbed to the concentrated halogen light used to focus and frame the image during setup (illumination is exclusively via flash during the imaging sequence itself). After soaking it in ethanol for a while to make sure it was dead, I mounted it for the rest of the images linked here.
The distinctive dorsal setae are likely an adaptation to living amongst
formica argentea specifically. The size and shape of the dorsal shell, and the setae length, thickness, and density closely resemble that of the
host's posterior gaster. The other ants probably could remove the mite from a host with their mandibles, but it would be difficult for them to distinguish it from a nest mate's gaster by feeling it in the dark of the nest. This lack of recognizability would not apply to the host it's attached to, however. The host may not be strong enough to dislodge the mite with a front leg alone, but signals to other ants could evolve to request assistance. There is a clue as to why such signals are not sent. Note in the
second image and its
closeup that the mite deposits a clear liquid droplet with right leg II at its point of contact with the eye. This may be inferred from the refractive distortion of the facets just inside the perimeter of the droplet and significant magnification of a triangular light pattern produced by light interacting with each facet in this part of the image. I speculate that this liquid is absorbed by the spongy pads at the tips of
leg pairs II through IV when they contact a secretory gland in the center of the mite's
ventral surface (genital area). The center appears in the
ventral view view to be within easy reach of these legs. The liquid would then be deposited onto the ant at the point of each leg's contact when the mite mounts. It may be a topical anesthetic which prevents the ant from noticing the mite.
The center appears in the
ventral view view to be within easy reach of these legs.
This image is a
CombineZP processed stack of 210 images with a 56 micron step taken with a Nikon CFI60 4X/0.1 microscope objective + Nikon 135mm F4 telephoto lens + Nikon D300 camera (magnification 2.7X; technique described
here).
Host worker:
Adult female, adult male, larva, protonymph, and deutonymph stages, respectively:
