Black spiky extruded capsule

[rjlittlefield]

I'll leave this as a "puzzle piece" for a short while, just because it looks so strange.

Does anybody recognize this structure?

Field width 2 mm.

Crossed-eye stereo:

--Rik

Technical: Mitutoyo 10X NA 0.28 objective on Raynox DCR-150, Canon T1i camera (APS-C sensor), illumination by two Jansjo LEDs diffused through white plastic hemisphere. 297 focus steps at 5 microns. 0.3 seconds at ISO 100, using EFSC.

[colohank]

Maybe a side view of an insect pupa on a leaf?

[MarkSturtevant]

The vertical striations resemble a stacking artifact that is common near a boundary of a stacked picture. But that seems out of place here.

[rjlittlefield]

Maybe a side view of an insect pupa on a leaf?

Very good! Yes, side view of an insect pupa on a leaf.

Now, what kind of insect, and why is the pupa black?

(Hint: the ID and the color can both be economically significant.)

The vertical striations resemble a stacking artifact that is common near a boundary of a stacked picture. But that seems out of place here.

I agree! But no, those are physical. Here is a 100% crop from one of the source images, run through Topaz Sharpen AI:

--Rik

[colohank]

Glasshouse whitefly, perhaps? The economic significance of its black color is way beyond my pay grade. A lot of whitefly pupae are black.

[MarkSturtevant]

I was just now thinking scale insect, but whitefly is close. It would be weird that a Hemipteran (a hemimetabolous insect) would have a kind of pupal stage, but they do.

[colohank]

Here are a couple of shots of Mulberry Whitefly pupae. I've found them on a Hackberry (green leaf) and an Ohio Buckeye (yellow leaf) in my backyard. I wouldn't know a Mulberry Whitefly if I found it in my soup, so I reached out to a number of sources for an ID. My son has a degree in horticulture, and he, in turn, reached out to a former entomology professor at Colorado State University. The professor made the ID.

[rjlittlefield]

Mine are similar to the greenhouse whitefly, though I would be surprised if exactly that species since mine came indoors from outdoor living in an area that freezes hard over the winter.

But the normal immatures of this species are pale greenish, like this:

Cross-eye stereo:

The black ones are special, and there begins a much longer story.

--Rik

[colohank]

The suspense is killing me. Why are the black pupae special?

[rjlittlefield]

Ah, sorry. I got so distracted investigating stuff that I forgot to post the solution to the puzzle!

The black pupae are parasitized, each one by a single small wasp that looks like this:

Total body length of the wasp is 0.8 mm, from tip of abdomen to front of face, excluding wings and antennae.

The small white thing in front of the wasp in this image may be one of the first instar "crawler" larvae of the whiteflies. I did not notice it there when I took this picture, and there's not enough resolution to be sure. (This is an actual-pixels crop from a 1X shot on Canon T1i, APS-C sensor.)

Here is a comparison of pupa exuviae, parasitized versus not:

Crossed-eye stereo:

The wasps are an important biologic control for whiteflies in greenhouses. There is a lot written about them, for example the slide presentation at https://webdoc.agsci.colostate.edu/bspm ... eflies.pdf .

If anybody wants some challenging micro subjects without the experience of "raising" them, you can buy parasitized pupae at quite a few places, for example https://www.arbico-organics.com/product ... e-shipping . (Oddly, they are not available through Amazon today, although they were, a couple of weeks ago.)

--Rik

[Pau]

Ah, sorry. I got so distracted investigating stuff that I forgot to post the solution to the puzzle!

The black pupae are parasitized, each one by a single small wasp ...

Very nice story and pictures, but I still can't locate the striated structure shown at your two first pictures

[colohank]

Thanks for the explanation.

[rjlittlefield]

Very nice story and pictures, but I still can't locate the striated structure shown at your two first pictures

The striations are part of the "vertical wall" around the perimeter of the pupa. They do not show in the last pictures because that view is looking down onto the top of the pupae. The vertical wall is visible in the green pupa at the center of the group photo (download/file.php?id=6340), but there the striations cannot be seen clearly because of lighting, coloration, and translucency.

I am not completely sure how the pupa forms. I see that the larval forms all have scale-type bodies that lie flat against the leaf. I think that as pupation occurs, the forming pupa greatly increases in volume by swelling away from the leaf surface and forming a new wall perpendicular to the leaf surface, around what was earlier the footprint of the scale. Probably the new wall is not strictly speaking an "extrusion" in the sense of semi-solid material being squeezed through an orifice, but whatever the process is, it ends up giving essentially the same result: the dorsal surface of the pupa looks much as it did in the last scale stage, but the sides of the pupa end up elevated and striated. In the one specimen that I crudely picked apart, the whole interior was filled with goo.

The style of pupa apparently varies a lot between species. https://webdoc.agsci.colostate.edu/bspm ... eflies.pdf , slide 12, notes that the Greenhouse whitefly pupa has these vertical sides, while the Sweetpotato whitefly does not.

--Rik