kitchen ants (pictures added)

[rjlittlefield]

It's the middle of winter, and all of a sudden some ants have discovered my kitchen.

There's nothing outside to eat, so they're loving the opportunity. My wife is not. But she's very tolerant of bugs in containers, so maybe we can work out some compromise.

Anyway, this ant found a small piece of peppermint candy lying loose on the countertop.





When I first saw it, it was carrying away the whole piece. I couldn't access the corner it was in, so I coaxed it onto a notecard that I could move to a more open space. In the process it dropped the candy and refused to pick it back up while I watched. But I see the piece of candy is now being attended by other ants, so I expect it will be gone soon.

Canon R7 camera with MP-E 65 lens at 2X and f/4 nominal (f/12 effective), single flash with small softbox head, ISO 400 with ACR enhanced noise reduction and Topaz sharpening.

The first image is a moderate crop, the second is actual pixels.

--Rik

[Planapo]

Rik,

You've managed to take an excellent picture of the head!

To me, the face of your ant reminds me of our dolichoderine Tapinoma species.
However, I am not familiar with the Nearctic dolichoderines or your ant fauna over there in general, of course.
For subfamily ID, a lateral view showing meso- and metasoma and the "linkage" between them, is helpful.

I understand the concerns of your wife, ants freely roaming the house can indeed be annoying. (Am speaking of own personal experience here.)
Now google tells me that currently your temperatures over there are around the same as ours here. So, I would expect any ants with nests in your garden are inactive, like ours are over here at this time of the year. Then I would expect that the ants, that show up active in your house, have their nest in a place that is benefitting from some soure of warmth. I hope the nest is not already in your house.

If I was you, I would try to indentify the ants to see whether it's a (so called) "pest ant" species that can cause trouble.

--Betty

[Planapo]

Rik,

meanwhile I've found some literature for you ... and your wife!

https://s3.wp.wsu.edu/uploads/sites/415 ... tpests.pdf

--Betty

[rjlittlefield]

meanwhile I've found some literature for you ... and your wife!

https://s3.wp.wsu.edu/uploads/sites/415 ... tpests.pdf

Lovely! "Identification and Habits of Key Ant Pests of Washington", published by Washington State University. I used to teach at the local campus. (Math, not biology!)

I expect to produce some decent images to check, but based on direct view through stereo scope, these ants match Tapinoma sessile. Those are known variously as odorous house ant, sugar ant, stink ant, and coconut ant. There's a Wikipedia article, https://en.wikipedia.org/wiki/Tapinoma_sessile . I confirm these ants have great fondness for sugar and water, and when I deliberately tested one with a fingertip, I smell (on the fingertip!) a distinct odor like blue cheese.

For the moment I have convinced them to mostly forego the countertops in favor of the pile of sugar that I provided for their convenience in a corner of the floor. (Yes, I did tell the wife. She found it amusing.) They also have access to a package of MaxAttrax Ant Bait , which specifically mentions sugar ants, but to be honest these ants seem to ignore the bait except as some sort of landmark on the route to the sugar.

--Rik

[brentbristol]

Nice! The tight crop highlights some great texture on his noggin!

[rjlittlefield]

For subfamily ID, a lateral view showing meso- and metasoma and the "linkage" between them, is helpful.

I confirmed the ID as Tapinoma in "Ants of North America: A Guide to the Genera", by Brian L. Fisher and Stefan P. Cover, https://www.amazon.com/Ants-North-Ameri ... 0520254228 .

So then...

Maybe this is a tighter crop than you had in mind, but I thought some of the details were interesting.

I am particularly interested in what appears to be a very thin fragile connection between two segments of the "linkage", dorsal of and separate from the much more robust connection that I think holds the ant together.

The following sequence zooms in on that fragile connection. All are cross-eye stereo pairs.







What is this bit of anatomy?

Optics were Mitutoyo 10X NA 0.28 and 50X NA 0.55, significantly cropped in all cases.

--Rik

[Macrero]

Ants in the kitchen can be really annoying. My wife hated them. I have mixed feelings

The candy thief has been well portrayed

- Macrero

[Planapo]

So Tapinoma it is... I am glad that my ant facial recognition hasn't let us down!

Common knowledge is that the insect body consists of three major divisions, with different major functions. These divisions are referred to as follows: the front division as head (or caput), the middle division (mesosoma) as thorax and the hindmost division (metasoma) as abdomen.

Now in the higher hymenoptera which the ants belong to, the original ovipositor has evolved into a sting. To make more effective use of this sting, it was advantageous to have the hind part of the body (metasoma) more freely movable than a broad attachment between the original thorax and abdomen, as seen in the more "primitive" hymenoptera (like the sawflies) allows for.
Hence, in the higher hymenoptera a constriction (" wasp waist") has evolved that allows for better motility of the last division of the body (metasoma).
But morphologically this constriction has evolved within the original insect abdomen: In the higher hymenoptera the original 1st abdominal segment, now referred to as propodeum (sometimes also called epinotum) is fused anteriorily to the original thorax. And hence it makes some sense to call this middle division of the body now just mesosoma or sometimes alitrunk, but not thorax anymore. And then to be consequent, to call the hindmost body division not abdomen anymore but just metasoma or gaster.
In ants the distinctive linkage of the mesosoma (here alitrunk) and metasoma (here gaster) consists of one or sometimes two segments, derived from the 2nd and 3rd segment of the original abdomen.
The first segment of the linkage is called the petiolus (original 2nd abdominal segment) and the second (if present, like in the Myrmicinae) is called the postpetiolus (original 3rd abdominal segment).

Here in your dolichoderine Tapinoma the "linkage" consists only of a small petiolus which is strip-shaped and depressed. This allows for raising the gaster in the air toward the dorsal side. This makes sense as in the Dolichoderinae the sting is reduced, is hence vestigal or absent. Instead the Dolichoderinae have evolved secretions, that are toxic or repellent for other ants/insects, which are released from glands of the gaster. It's probably what you can smell as blue cheese odour in your T. sessile.

Ants of other subfamilies with a sting present, often have a rather large petiolus (and sometimes postpetiolus) with dorsal hump and muscles, enabling them to bend the gaster to the ventral side, to thrust the sting between their legs and place them into the target that way.

Now, these are great images/stereos, Rik!
Such quality images really deliver evidence for first morphological studies and discussion without the imperative use of an SEM.

Like you, I am particularly intrigued by what looks like a peg protruding from the alitrunk against the anterior side of the petiole. And it looks to me that on the opposite side, the anterior side of the petiolus, there seems to be a patch of hairs. I wouldn't expect it to be a solid, thin conncection. I would rather expect the protrusion of the alitrunk to be touching the hairs from the opposite side of the petiolus.

(But then cross-eyeing at the last stereo pair again, I see your point that it looks like some more solid connection.)

Because these structures must have some kind of function, this would make sense as follows:
My speculation would be: Protruding structure touches and bends and thus stimulates mechanosensory hairs according to the relative position of the petiolus towards the alitrunk.
(Or if the connections was really solid, then I would expect it to be bedded flexibly in this socket structure, like the protrusion on the alitrunk would be suspended by membranes in this socket, and the movement could then be registered by sensory cells in the socket too, and not, or not just, by sensory hairs on the opposite side ...)

In both ways the organism gets sensory feedback about the position/movement of the petiolus and gaster relative to the alitrunk and can sense gravity.
Such sensory feedback in organisms is generally called proprioception.

Bottom line, the answer to your question:

What is this bit of anatomy?

would be:
A mechanosensory receptor.

--Betty

[rjlittlefield]

Bottom line, the answer to your question:

What is this bit of anatomy?

would be:
A mechanosensory receptor.

Thanks for the explanation -- most appreciated!

But on further review, I'm thinking it's not the full story...

In the previous picture the subject was photographed soft, with the gaster pulled down (ventrad), so as to open the V at the waist so that I could see the bits of interest. I did not know what effect that pulling might have had on the anatomy.

So, I prepared a different specimen by dropping in boiling water, soaking in acetone for a day, and letting it dry in whatever position it naturally assumed. That resulted in the V totally closed, so I simply broke off the gaster to photograph the waist.

Here is the dorsal view revealed by that process (cross-eye stereo pair):



I find this intriguing, but I'm still not sure what to make of it. In looking through the illustrations in "Ants of North America", I do not see anything visually similar except for Technomyrmex (pg 146) and possibly Forelius (page 87). At https://www.antwiki.org/wiki/Tapinoma I find this snippet:

Within the Dolichoderinae two genera, Tapinoma and Technomyrmex, are isolated in their female castes by the synapomorphic extreme reduction of the petiole and its accommodation in a longitudinal groove or impression in the ventral surface of the first gastral tergite, which overhangs and conceals the petiole in dorsal view when the mesosoma and gaster are aligned. The petiole is so reduced in these two genera that in profile there is no trace of a node or scale; at most there is a very short raised surface immediately behind the peduncle. The function of this raised surface is to provide an insertion-site for the exterior levator muscle of the petiole.

Searching on "exterior levator muscle" finds only the same or very similar text at multiple sites. I can't be sure what "exterior" means here, but I'm getting the feeling that in this group the petiole levator muscle has managed to get routed completely outside the sclerotized exoskeleton, wrapped in its own membranous covering that is separated from the rest of the exoskeleton to form a topological hole. It would be the devil's own time to molt again, but of course that's not required.

I wrote to David Lubertazzi, who added that text to the Wiki, but got back an automatic reply indicating that he'll be unavailable for quite a while.

Any thoughts?

--Rik

Mitutoyo M Plan 20X NA 0.42, with Raynox DCR-150 tube lens, 2 micron focus step. Two electronic flashes through hemispherical diffuser. ISO 100, 1/4 second with full electronic shutter and mid-exposure flash.

[CrispyBee]

Here is the dorsal view revealed by that process (cross-eye stereo pair):




--Rik

Mitutoyo M Plan 20X NA 0.42, with Raynox DCR-150 tube lens, 2 micron focus step. Two electronic flashes through hemispherical diffuser. ISO 100, 1/4 second with full electronic shutter and mid-exposure flash.

That's a beautiful shot, both aesthetically and scientifically!
Your 3D stereo images are so well suited for visualising the structure of these parts, regular 2d photos are often times confusing and require a lot of time and effort to decipher in terms of perspective and how certain parts work or fit together.

Brilliant!

It also goes to show how well Zerene is suited for scientific documentation.

[Planapo]

Excellent work Rik! Thanks for continuing it, and taking us along. Following this is most interesting and instructive!

But on further review, I'm thinking it's not the full story...

Considering the further most helpful information you have provided, I do agree!

With your newly added picture (the stereo rendition helps so much more with visualising the shape of the structures! ) I abandon in part my view, i. e., that the thin protrusion coming from the alitrunk as seen in the previous images, could function as a part of the mechanosensory proprioception. The latter could be accomplished alone by the setae we see coming from the petiole, touching the horseshoe-shaped ridge on the alitrunk.

With that citation from Brian L. Fisher and Barry Bolton you've found:

Fisher and Bolton (2007) - The petiole is so reduced in these two genera that in profile there is no trace of a node or scale; at most there is a very short raised surface immediately behind the peduncle. The function of this raised surface is to provide an insertion-site for the exterior levator muscle of the petiole.

I think we can be positive that by bending the gaster ventrad in order to expose the waist, you have exposed, and maybe partially severed, this astonishingly separated and isolated exterior levator muscle. So the protrusion we see in your initial photos would be this exposed exterior levator muscle. In your last stereo photo we see this extereor levator muscle inserting at the orifice in the alitrunk which is surrunded by that horseshoe-shaped ridge. And on the opposite site, there still seems a thinner part of this muscle inserting at the mentioned raised surface of the petiole.

I'm getting the feeling that in this group the petiole levator muscle has managed to get routed completely outside the sclerotized exoskeleton, wrapped in its own membranous covering that is separated from the rest of the exoskeleton to form a topological hole.

I agree, that's what it looks like! A quite separated muscular connection tergally above the joint connecting alitrunk and petiole.
I didn't know about the muscular connection being that seperate before.
All makes sense now, and one can imagine well how the mechanism works when the muscle shortens to raise the gaster tergad.

Always a pleasure to follow your investigations, Rik!

--Betty

[Planapo]

Hah! You gonna like this, Rik!

Digging in the literature, I have found good SEM images of the very morphological structures in our European Tapinoma erraticum which beautifully show and confirm what we see in your photos: How separated this levator process is in Tapinoma, here compared to another dolichoderine.

But see for yourself the images C and D here:

https://www.researchgate.net/figure/Pet ... _232677257

--Betty

[rjlittlefield]

That's a beautiful shot, both aesthetically and scientifically!

Your 3D stereo images are so well suited for visualising the structure of these parts, regular 2d photos are often times confusing and require a lot of time and effort to decipher in terms of perspective and how certain parts work or fit together.

Brilliant!

It also goes to show how well Zerene is suited for scientific documentation.

Thanks! I happily confess that aesthetics in my images are always due more to luck than intent.

But it is nice when things come together and I can make an image that's pleasant to look at as well as revealing whatever structure I wanted to see.

It is especially nice when that structure is as tiny as we see here. The subject area shown in that image is only 0.13 mm wide. The entire image covers an area that is smaller than the finest line pair that can be resolved by unaided eyes.

But on my monitor it displays 1000 times larger, entirely sharp, and in 3D -- marvelous! And this magic can be done routinely, using only equipment that fits on a desk, requires no vacuum or metal vapors, and costs less than many used cars -- amazing!! Surely I will never tire of this before my time is done.

For size reference, here is one of the ants in more familiar surroundings:

Always a pleasure to follow your investigations, Rik!

And a pleasure for me, to have friends to do it with! (Thank you for tracking down that article!)

This is the first time for me too, encountering a muscle that is outside the rigid exoskeleton.

But the more I think about it, the simpler it seems for such a structure to form as part of the adult in a holometabolous life cycle.

I wonder what the evolutionary pressures are, that keep it from happening more often?

--Rik

[Sym P. le]

Rik, your work is amazing. I LOLed when I saw your candy cane ant 'cause that's exactly what I do with volunteer at home specimen, but not with these results.

Further to this, the exterior process is interesting and I believe I've seen a similar structure in midges associated with the wing mechanism. I posted a 3D image here viewtopic.php?f=26&t=44582&hilit=midge. I've been curious about it ever since and haven't found any information on it or it's prevalence in the insect world.

[rjlittlefield]

Rik, your work is amazing. I LOLed when I saw your candy cane ant 'cause that's exactly what I do with volunteer at home specimen, but not with these results.

Further to this, the exterior process is interesting and I believe I've seen a similar structure in midges associated with the wing mechanism. I posted a 3D image here viewtopic.php?f=26&t=44582&hilit=midge. I've been curious about it ever since and haven't found any information on it or it's prevalence in the insect world.

Thank you for the kind words and the pointer to your image.

For my eyes, your image does look like maybe it shows a linkage with holes in it, at the base of the wing. I cannot tell for sure whether any membrane completely fills in the area between the major structures. If it does not, then that would definitely qualify as what I've called a "topological hole". I read that flies "use indirect flight muscles to oscillate the thorax to flap their wings and a small set of direct muscles to steer them" (The Complete Insect: Anatomy, Physiology, Evolution, and Ecology, David A. Grimaldi, page 145). So, if any of the muscles are exterior, I guess they would be some of the ones for steering. Or perhaps the holes, if they exist at all, are just voids between the major veins. We would need more pictures to tell for sure.

In any case, after pondering the issue for some days I think the main downside with topological holes is just that they are holes, not exactly what forms them. The nasty thing about a hole is that long thin stuff can get run through it, and if that happens then the critter with the hole is leashed in place with no simple way to get loose. For a hole to persist as an anatomical feature, its value must exceed the cost of that liability. The value seems small -- a little less membrane to grow -- so the liability must be small also. In the case of these ants, I think it's notable that the exterior muscle lies in a part of the anatomy that is usually well protected by other surrounding parts such as the large gaster. But it's a pretty special case.

So, my guess is that even if we look very close, we won't find many of these holes in other places.

--Rik