How to make a diagram of an insect from an insect specimen

The lab I work in is partially a systematics lab, and part of the work of systematists is describing insects, part of which is creating diagrams that clearly show diagnostic traits of the insects. Some of these diagrams only include parts that differ between species- often reproductive organs. This is approximately the process my lab mate uses to draw diagrams from insect specimens. (Hers are slide mounted, so she doesn’t use the stackshot- instead we have a microscope with a camera attachment). I am not a systematist- I do mostly ecological modeling and informatics- so this is more of a general guide.

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This dead Romaleidae is named ‘Cuppy’. I cut Cuppy in half so I could fit it under the camera and now it looks very sad

Step 1: Find an insect

There are insects basically everywhere. This should be pretty easy.

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Step 2: Take an image of the insect

Taking pics of insects is harder than it sounds because it’s hard to focus on the whole insect at once and gets harder the smaller they are.

Because of all the systematics stuff we have this rig set up in our lab. It is composed of a DSLR, attached to an arm that moves up and down and a stackshot.

The rig slowly moves the camera up or down while taking images at consistent intervals.

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This controls the movement and capture of the camera

The resulting images are loaded onto a computer program (z-stack) which integrates all the images together to make one cohesive image where all the insect parts are in focus. Unfortunately, I can’t show you an image of that process because the computer we usually use for it started bugging out yesterday and we haven’t fixed it yet.

So far, being a scientist has been 20% repairing computers.

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Step 3: Convert the image into greyscale and increase the contrast

Here’s my combined image. If I hadn’t done the stacking thing, you wouldn’t be able to see both the tips of the antennae and the legs clearly in one image. You can see some relics of the stacking program around the head.

Chloe and I think that it looks like it’s posing for a school photo.

I converted the image into black and white using photoshop (Image -> Mode -> Grayscale) and then increased the contrast (Image -> Adjustments -> Curves…).

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I spilled something pink on one side of the picture. Hopefully that doesn’t make it into my final diagram!

Once I had the image in black and white and had increased the contrast, I printed it out, but it might be easier and more convenient to do the rest digitally if you’re comfortable with photoshop or gimp.

Step 4: Trace the image lines in sharpie

Tracing over the parts of the image I think are the boundaries helps me later when I’m trying to trace the photograph onto another piece of paper, because at this point it’s pretty hard to distinguish the different sections of the insect, and tracing is even harder. If you’re doing it digitally, you’d skip this step.

Step 5: Trace the lines onto a new piece of paper

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I put the photo behind a piece of plain paper (tracing paper would be better) on a light plate and do my best to follow the lines I had marked earlier. I do this in pencil, so I can make corrections if I mess up. I don’t have an image of the result of this process- it didn’t look as clean as it does here.

Step 6: Check the real insect against the photo and drawing

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So after I’ve done my best to trace the photo, I still have a lot of questions about what’s happening- are those little hairs? Which parts are hardened cuticle and which are membrane? How do these two parts fit together? At this point I refer back to my original insect. By examining it under the dissecting microscope I can make better guesses about which parts are which. I can try to determine which parts are membranes (by poking at them mostly), and I can look for small features I might have overlooked (like ocelli (small, simple eyes) and setae (hairs)).  I will also consult the full color images I took during this process.

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This dissecting microscope has a special arm that lets you see your drawing superimposed over the image of your specimen

 Step 7: Attempt to identify and label the parts.

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At this point, I’m ready to make some guesses about what I’m looking for. This is where having memorized insect body parts comes in handy. I also search the internet for diagrams people have previously done of similar insects.

This is my intermediary drawing. You can see I have only drawn the head; the dotted lines indicate the thorax, which I chose not to draw. I also only have outlines. For the purposes of making a diagram I’m not going to include any information about texture or color.

Step 8: Trace the intermediary image onto the final image

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After going back between the microscope, the full color images, and the diagrams, I have what I think is a pretty good idea of what the insect looks like. But my intermediary drawing is really sloppy, so I want to trace it again to produce a clean, clearly labelled version. I put it on the light plate again and trace over the lines very carefully. You can see that I have stippled (put small dots in) some areas and some lines are lighter than others. The stippled areas are the membrane and the thin lines indicate sutures or sulci; ridges in the sclerotic plates rather than boundaries where the plates meet.

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Here are all three of my images; my original photo with the traced lines, the intermediary image and the final image.

Step 10: Label the diagram.

Finally, I clean up the lines on my drawing, making sure all the widths are consistent and the lines are smooth (‘not sketchy’ is how Nate describes it). Then I add the labeling, trying to write neatly (and failing) and using a small ruler to point to the objects. Finally, I add the insect name. When I did this I didn’t know that lubbers were in Romaleidae, and I could have looked it up but I didn’t.

And here’s my final product:

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Apparently our scanner is really bad, so I took it with my phone
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