parasitic wasp from bug eggs

[rjlittlefield]

I found some bug eggs that looked parasitized, so I was prepared for small black wasps to emerge.

But I was totally not prepared for what I saw when I looked close.

This is crossed-eye stereo:


This is apparently something like a samurai wasp, though the group is so large that any specific ID is not likely to be correct. The samurai wasp, under consideration for biocontrol of brown marmorated stink bug, is Trissolcus japonicus, Hymenoptera:Scelionidae. https://en.wikipedia.org/wiki/Scelionidae describes the family as

a very large cosmopolitan group (over 3000 described species in some 176 genera) of exclusively parasitoid wasps, mostly small (0.5–10 mm), often black, often highly sculptured, with (typically) elbowed antennae that have a 9- or 10-segmented flagellum.

Um, yeah, "highly sculptured" seems like an excellent description!

Here is an overview:



As shown here, the abdomen has a distinctive and unusual forked shape. But other specimens from the same brood do not have the same shape, and I'm pretty sure the one shown here is just a quirk of shrinkage as it dried out.

Finally, here is a close crop showing the hamuli, just because I was curious. These are small, but not quite as small or fragile as the ones from my whitefly wasps, HERE.



All images are from the same stack, 267 frames at 0.003 mm step size, shot with Mitutoyo M Plan Apo 20X NA 0.42 on Componon 135 mm f/5.6 as a tube lens. Nominal magnification would be 13.5X, measured is 13.6X. Two flashes through two separated layers of matte mylar diffusion film. Synthetic stereo at +-5 degrees.

--Rik

[rjlittlefield]

Recording here a link that I definitely don't want to lose: http://hol.osu.edu points to the Hymenoptera database at Ohio State University. Today that redirects to https://mbd-db.osu.edu/hol/taxon_name/3 ... f422668e24 , which is part of Ohio State University's Museum of Biological Diversity database.

Just for genus Trissolcus they report "Specimens | Count: 16061". There are not nearly that many images, but even those run to 68 pages at apparently 25 per page, so 1700-ish of them.

For whatever it's worth, none of the images for Trissolcus japonicus match the pattern of pits in my photo, and I haven't found another species that does either.

--Rik

Edited to add: more references
https://www.northeastipm.org/stopBMSB/a ... alamas.pdf
https://mbd.osu.edu/people/talamas.1
https://jhr.pensoft.net/articles.php?id=4987 "Key to Nearctic species of Trissolcus Ashmead (Hymenoptera, Scelionidae), natural enemies of native and invasive stink bugs (Hemiptera, Pentatomidae)"
https://jhr.pensoft.net/articles.php?id=4661 "Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae) emerges in North America"

[dy5]

Rik -

Great images and story! The sculpting is amazing - any idea what function it might serve?

Cheers, David

[Sym P. le]

Nice images and workup, as usual. I captured a video of Trissolcus sp. a few years back and was impressed with the sculpting and definition as well. It also put on a good show. Apparently they remain close to their brood to fend off subsequent parasitoids so possibly there was an egg mass on the underside of the leaf.

[rjlittlefield]

Nice images and workup, as usual. I captured a video of Trissolcus sp. a few years back and was impressed with the sculpting and definition as well. It also put on a good show. Apparently they remain close to their brood to fend off subsequent parasitoids so possibly there was an egg mass on the underside of the leaf.

Thanks! Your video is very interesting and must have been quite challenging to shoot. I did not know about the wasps' behavior of guarding the brood.

Great images and story! The sculpting is amazing - any idea what function it might serve?

Thanks!

I have no good idea why this group has such extreme sculpting.

I decided to use this question to give ChatGPT another try. The exchange went like this:

Me: I have a question about entomology. As background information, some small wasps that are parasitoid on the eggs of other insects have bodies that are heavily sculptured, meaning that they are covered with large ridges and pits. An example is the samurai wasp, Trissolcus japonicus. Do you know what has been published, regarding the function of that sculpturing?

ChatGPT
The sculpturing of parasitoid wasps' bodies, such as the samurai wasp (Trissolcus japonicus), has been the subject of several studies. The functions of this sculpturing are not entirely understood, but there are several hypotheses:

1. Mechanical Protection: The ridges and pits might provide structural strength to the exoskeleton, helping to protect the wasp from physical damage or predation.
2. Camouflage and Mimicry: The sculpturing could aid in camouflage, helping the wasps blend into their environment or mimic other insects or objects to avoid predators.
3. Sensory Enhancement: The ridges and pits may play a role in enhancing sensory perception. They could aid in the distribution of sensory hairs, improving the wasp's ability to detect chemical or tactile cues in its environment.
4. Surface Area for Pheromone Dispersion: The increased surface area provided by the sculpturing might help in the dispersal of pheromones, which are crucial for communication and mating.
5. Aerodynamics: The sculptured surface might influence the wasp's aerodynamics, potentially aiding in flight stability and maneuverability.

Research specific to Trissolcus japonicus might be more limited, but these general hypotheses are often applied to other parasitoid wasps with similar body sculpturing. For a deeper understanding, you might look for studies focusing on the morphology and ecology of these wasps.

Would you like me to find some specific studies or reviews on this topic?

Me: Yes please, do find some specific studies or reviews.

ChatGPT

Searched 3 sites

Research on the function of body sculpturing in parasitoid wasps like Trissolcus japonicus has provided several insights, though the exact purposes remain largely hypothetical. The sculpturing, which includes ridges and pits on the wasp's body, might serve multiple potential functions:

1. Mechanical Protection: The structural strength provided by the sculpturing could help protect the wasps from physical damage or predation. This is especially important given their small size and the hostile environments they navigate.
2. Enhanced Sensory Perception: The sculpturing might aid in the distribution and functioning of sensory hairs, improving the wasp's ability to detect chemical or tactile cues essential for locating hosts and navigating their environment​ (SpringerLink)​​ (Oxford Academic)​.
3. Camouflage and Mimicry: These physical features could assist in blending into their surroundings or mimicking other objects or insects to evade predators.
4. Pheromone Dispersion: The increased surface area created by the sculpturing may help in the effective dispersal of pheromones, which are vital for communication, especially in mating behaviors and locating suitable hosts.
5. Aerodynamics: The sculptured surface might also influence the wasp's aerodynamics, potentially aiding in their flight stability and maneuverability.

These hypotheses reflect a combination of adaptive advantages that the sculpturing might provide, contributing to the wasps' survival and reproductive success. Specific studies focusing on Trissolcus japonicus and related species continue to explore these functions in greater detail.

For more detailed information, you can refer to studies such as those found on Springer and ScienceDirect, which discuss aspects of the wasp's morphology and its ecological interactions​ (SpringerLink)​​ (Oxford Academic)​.

This exchange with ChatGPT 4o strikes me as a big step up from my earlier experiences with the previous version. In this case it did offer to find references, and when I accepted that offer, it apparently did a real-time search and returned links to real articles of possible relevance. I'm disappointed that the abstracts of the returned references don't mention anything about sculpting, but at least they're not totally bogus like ChatGPT used to do.

Of course the aspect I find particularly interesting is that these wasps are so highly sculpted compared to other parasitoid wasps of similar size. It seems like that body armor must cost a lot of resources to produce, so why do these critters put those resources into elaborate sculpting rather than, say, more eggs? A clue to that may lie in Sym P. le's note that these wasps are prone to guarding their brood. If that behavior means that they parasitize only a single egg mass of the host bug, then the wasps would get no benefit from making more eggs, while improved armor could be helpful at almost any level.

--Rik

[dy5]

Rik -

Your point about comparison with other similar wasps makes great sense. On one hand, the strong difference is what makes the sculpting so puzzling. On the other hand, the comparison might be a clue to a major difference in behavior.

I stumbled across another possible explanation beyond what the (improved) ChatGP provided. Instead of having muscles directly attached to the wings, wasps have an indirect flight mechanism that uses elastic deformation of the thorax to move the wings up and down. Maybe the sculpting changes the mechanical properties of the thoracic structures in a way that benefits some unusual flight requirements faced by this particular species. Not that I have any idea what those requirements might be ...

For some info on flight in tiny insects: this paper is good. (I'll be happy to email a PDF if you have trouble accessing it).

Cheers, David

Edit: Or maybe the sculpting has to do with control of the wing joints rather than with powering the up-down wing movement.

[rjlittlefield]

For some info on flight in tiny insects: this paper is good. (I'll be happy to email a PDF if you have trouble accessing it).

That exact link seems to be broken (https://www.sciencedirect.com/science/article/pii/S0959438816301258url).

But when I removed the unusual three letters "url" from the end of the URL, I reached a paper titled "Neurobiology and biomechanics of flight in miniature insects" by Sanjay P. Sane.

There, clicking the "View Open Manuscript" button got me a readable version of the paper including images.

Thanks for the reference!

--Rik