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Parasitic wasp cocoons guarded by host caterpillar

Notes:

Thanks to John La Salle for insights on what's going on here, and also this website which describes the whole process in gruesome detail, http://www.environmentalgraffiti.com/ani... . This green caterpillar, about 2cm long, is sitting on (guarding) a cluster of fuzzy egg-like things on a plant in our backyard. The egg-like things are the cocoons of a parasitic wasp, probably Braconidae (Microgastrinae) or Eulophidae (Euplectrus), which laid its eggs inside the body of the caterpillar. The eggs have developed inside the caterpillar, eating it from the inside out. According to Environmental Graffiti, "the caterpillar continues to feed and balloon, consuming one and a half times as much food as would one of its un-parasitised kin" which explains the completely stripped leaf in shot 3. And then the larvae come busting out of the caterpillar because there's not much space left in there after they've eaten everything except the vital internal organs that keep the caterpillar alive. So that's all pretty horrifying, but NOW: "So much is the caterpillar under control that it spends its remaining days repelling the attacks of other parasitic wasps that target the fresh larvae, its natural aggression exploited in a last mock-heroic stand before it finally succumbs to starvation. This bizarre corruption of the caterpillar’s behaviour is believed to be caused by the same wasp virus that infected it weeks before, and which now invades its brain. Watching vigilantly over its precious charges, the caterpillar’s paternal instinct survives till death, as it ushers in the metamorphosis of a new generation of parasitic wasps." Part II - Shots 5 & 6 added on April 7. No movement on the egg-like things, but the caterpillar seems to have moved slightly. Any progress will have to come as a second spotting!

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23 Comments

Jacob Gorneau
Jacob Gorneau 9 years ago

What an informative series and great shot!

KarenL
KarenL 9 years ago

Fu fact! The eggs of a parasitic wasp develop inside its prey, in this case a caterpillar, eating it from the inside out. The caterpillar continues to feed, consuming one and a half times as much food than normal, until the wasp larvae bust out after consuming everything except the vital internal organs that keep the caterpillar alive.

The caterpillar continues to live but its brain is controlled by a polydnavirus – one of a unique group of insect viruses that have a mutualistic relationship with some parasitic wasps. The caterpillar spends its remaining days repelling the attacks of other parasitic wasps that target the fresh larvae until it finally succumbs to starvation.

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ShannaB
ShannaB 9 years ago

PS Leuba, I agree it's amazing how 'intact' the caterpillar looks - I was skeptical at first because of that (I imagined its stomach exploded open like in 'Alien' or something). The larvae have super sharp little razor teeth that they use to cut their way out; I'm not sure how the caterpillar stays in one piece during this process but that's what seems to happen!

ShannaB
ShannaB 9 years ago

Thanks Maria, Leuba and Dafne. Andrea, yours even looks like the very same type of caterpillar!! I wonder if this type of caterpillar is a regular victim of such attacks? An update on mine... I went out to check this morning and the caterpillar has disappeared, perhaps it got picked off by a bird. I'm still keeping an eye on the cocoons. No progress this afternoon!

Andrea Lim
Andrea Lim 9 years ago

That was very interesting Shanna. Thank you for sharing the notes with us. It helped me also, because I had the same caterpillar and cocoons. http://www.projectnoah.org/spottings/208...

DafneInFiamme
DafneInFiamme 9 years ago

Wonderful shots and really interesting note!!! Congrats!!!

Leuba Ridgway
Leuba Ridgway 9 years ago

Brilliant spotting, Shanna ! the caterpillar looks a little too healthy if it's body has already expelled all those little wasp larvae ?! what a bizzare and sad story...still, it's fantastic that you have been able to witness this phenomenon !!

Maria dB
Maria dB 9 years ago

Gruesome but really interesting

Mark Ridgway
Mark Ridgway 9 years ago

Yep - that's what those cotton buds are.

Mark Ridgway
Mark Ridgway 9 years ago

Oh my goodness... Now that's a cool spotting. :)

ShannaB
ShannaB 9 years ago

Thank you John, I'll keep watching! Thanks Mayra & Lauren. Lauren, I'm pretty sure the caterpillar is still alive. I don't want to poke it or anything as I don't want to interfere, but it seems to have moved slightly overnight (under its own steam).

LaurenZarate
LaurenZarate 9 years ago

Very interesting story and pictures, and yes, gruesome! Hope you can keep watching and show us the wasp parasite. If you touch the larva, does it move, or is it dead now.

MayraSpringmann
MayraSpringmann 9 years ago

Great séries!!

John La Salle
John La Salle 9 years ago

Yes - there is some very cool behaviour in these parasitic wasps that really takes us into the realm of science fiction. If you manage to get a shot of an adult when they emerge I can tell you where it belongs. If it is a microgastrine braconid (most likely) the genera can be quite difficult to tell apart (and I don't know that group very well) - but I could at least tell you it was a microgastrine.

ShannaB
ShannaB 9 years ago

Notes updated. John, thank you so much for your insights! Argy, is that ringing the right bells with what you saw?

StephenSolomons
StephenSolomons 9 years ago

Now THAT is cool!!!

ShannaB
ShannaB 9 years ago

OK, this is even MORE horrifying. It seems to be guarding them. From this page: http://www.environmentalgraffiti.com/ani... "So much is the caterpillar under control that it spends its remaining days repelling the attacks of other parasitic wasps that target the fresh C. glomerata larvae, its natural aggression exploited in a last mock-heroic stand before it finally succumbs to starvation. This bizarre corruption of the caterpillar’s behaviour is believed to be caused by the same wasp virus that infected it weeks before, and which now invades its brain. Watching vigilantly over its precious charges, the caterpillar’s paternal instinct survives till death, as it ushers in the metamorphosis of a new generation of parasitic wasps." OK, I'm convinced.

ShannaB
ShannaB 9 years ago

Here's an update - the caterpillar has moved slightly and I can see its underside, which appears to be unmolested. See shots 5 & 6. What do you think?

ShannaB
ShannaB 9 years ago

Wow John, a horror movie in our own backyard!!!!! I'm going out there to take another look this morning and see if there is any progress!!!

Mark Ridgway
Mark Ridgway 9 years ago

Uh oh the brain is going... I saw a cluster exactly like this very recently... now what was it !?

John La Salle
John La Salle 9 years ago

Very cool. The fuzzy egg-like things are the cocoons of parasitic wasps. They have attacked the caterpillar and more than likely devoured a goodly portion of what's inside it. They then emerge from the caterpillar (which at this point is moribund if not dead), spin their cocoons and develop into adults. If you toss the whole thing in a jar you will get the little adult parasitoids emerging soon. Most likely Braconidae (Microgastrinae) or Eulophidae (Euplectrus)

ShannaB
ShannaB 9 years ago

Hahaha, thanks Stephen!! Very insightful!!! ; )

StephenSolomons
StephenSolomons 9 years ago

Looks @ fuzzy egg things. Yes that is what they are!

ShannaB
Spotted by
ShannaB

Maroochydore, Queensland, Australia

Spotted on Apr 6, 2013
Submitted on Apr 7, 2013

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