A trail of ants

Tapinoma sessile odorous house ants recently set up a thick trail through our kitchen. Rather than kick them out, I laid down white mylar to serve as a clean backdrop and took some photographs.

The above image is a composite. I cloned in a single individual from a second photograph to fill a gap. I don’t typically alter major elements of my images this way, but I felt the photoshopping to be excusable for an illustration.

Can you guess which ant was added?

photo details:
Canon EF 100mm f2.8 macro lens on a Canon EOS 7D
ISO 200, f/13, 1/160 sec
3 diffused off-camera strobes

12 thoughts on “A trail of ants”

  1. Those of you going with “third ant from the bottom” are correct. I’m not sure how you’d know, though. It’s a smaller individual, sure. I chose it because it was in the right part of the frame, in the right orientation, so that the light reflections, focus, etc. should be consistent.

    I did not appreciate how much color and size variation there is among these supposedly monomorphic ants until I started working up the photos. Individuals are really quite different from each other.

    1. The third ant from the bottom is technically the brightest one of the bunch. I brought the photo into ImageJ, selected each ant with a similarly sized ROI and calculated the mean gray levels. From left to right, they are approximately: 237, 241, 243, 241, 241, 238, and 235. Since they gray levels go from 0 (black) to 255 (white), the third is the brightest.

      An interesting test would be to artificially brighten one of the other ants just a tiny bit and have us guess again.

  2. Elise Fallson

    Nice photographs. I actually studied T. sessile for a bit years ago, brings back memories… (:

  3. One thing I’ve noticed about these around here is the spring workers tend to be big and black, the summer workers small and gray. Elise, was this your experience too?

  4. I am truly amazed that anyone could figure this one out. Was it due to the shape or orientation of the head, or that it was just slightly smaller than the others. Never the less, whatever the feature was that made it stand out, I am impressed with Jason and Rodolfo’s observation skills.

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