I spent the whole night trying to write up a lab report for insect physiology class at UIUC on a project using environmental scanning electron microscope (ESEM). I was not able to finish the paper with high quality but our teacher Dr. Marianne Alleyne was nice enough to give two more days.
Regardless, let me share a bit about what we did. One of our group members Josh Gibson studies trap-jaw ants with Dr. Andy Suarez. He had an idea to look at (1) spongiform tissue and (2) presence of zinc element on mandibles in Strumigenys ants.
A little background from my report:
“The mandibles of insects are a pair of highly modified appendages in mouthparts with main purpose of food manipulation, prey handling, and nest building. The functional nature of the insect mandibles, therefore, requires them to be extremely hard compared the rest of integumentary system (Hillerton & Vincent 1982). One way to increase the strength of mandible cuticle is by incorporating metal elements such as zinc and manganese and sometimes, calcium (Quicke et al. 1998; Schofield et al. 2002; Cribb et al. 2008a; Cribb et al. 2010). The presence of zinc in mandibles has been confirmed in many insect groups, for instance, grasshoppers (Edwards et al. 1993), ants (Schofield et al. 2002; Hillerton et al. 1982), termite (Ohmura et al. 2007; Cribb et al. 2008b), and beetles (Hillerton et al. 1984). It is also found in spiders and scorpions chelicera (Schofield et al. 1989).“
Hm. I am plagiarizing myself.
So we should look at the mandibles. We wanna see if zinc is also present on the mandible, and in particular, the teeth on the mandible.
Let’s just look:
The images were taken with backscattered electron detector (BSD) within the ESEM chamber. Do you see the teeth (or denticles) of the mandible, are highlighted? Those are the zinc! When I am making the beetle crafts, I always imagine an entire robotic insect made with metal parts. Now I learn that they actually are equipt with metal in the jaws!
Here is the X-ray photoelectron spectroscopy spectrum of each point for the four specimens, (the point was numbered in the figure above).
If you really want to look into the figure, you can zoom in to see the peak of zinc in the diagram 2 and 3 in each species.
So this is how the ant looks like (Strumigenys gundlachi, from Antweb):
Horace Zeng 