Just wondering... How much more of the plant does the hornworm devour before the eggs hatch and the wasps destroy it?

the eggs are laid inside the worm and come out as cocoons (what you see on the outside). the gruesome thing about this is the larvae basically eat the worm inside while it's alive.. once they emerge out of the cocoons the worm dies anyway shortly after - whether they attack it or not, it was doomed as soon as the wasp laid the eggs inside the worm. normally when the worm is done feeding on the vegetation, it buries itself in the ground and goes into its final phase turning into a moth, this one didn't have a chance..

"How much more of the plant does the hornworm devour"

Usually the hornworm stops feeding by the time a big load of wasp pupae are anchored on it, or if it was parasitized when smaller (second stage instar). But it can continue to eat a few leaves if the wasp cocoon load is low or it was parasitized a little larger (third stage instar).

Wasps pupate in 5 days after the white cocoons are formed, after sucking the caterpillar's insides, where they've already been eating hornworm plasma for two weeks. The damage has almost entirely done to the hornworm by that time, and if you cut it open you will find its organs and mostly a bag filled with wasp larvae before they pupate. The mother wasp infects the caterpillar with a symbiotic virus and chemicals when laying her eggs inside the tissue to modify the caterpillar's chemistry and immunology to benefit her offspring, and a couple days later the wasp larvae hatch and only eat the tissue of the hornworm that is non-vital with the strategy to keep the caterpillar alive/fresh, including prolonging the caterpillars time it spends in the larval stage.

Several hours before the pupae appear, the hornworm suddenly decreases mobility considerably if not completely, but before that it has fed normally. This is probably caused by the wasp larvae secreting some chemicals for their own protection because the caterpillar could otherwise eat the pupae too, if it still had enough muscle space to give it a wide enough degree of motion. If the hornworm continues moving it is mostly in a wandering/non-feeding condition, and it will not be able to make a cocoon itself. If there are only a few wasp pupae visible, it may be 2-3 days for the rest to appear, and 100 cocoons is a typical brood.

You can prune carefully the petiole with the caterpillar if you want to be certain not to feed the caterpillar more, and put it away from the tomatoes somewhere safe in the garden for those few days, somewhere where ants or other predators won't get it. The wasps will do fine and the caterpillar will continue to live thanks to the modified, suspended metabolism the wasps cultivated when harvesting it.

Purdue Entomology video, caterpillar is still alive - notice movement 0:30-1:00 and even 1:30-2:00, also notice caterpillar is not feeding at all after first wasp larvae piercing skin right up to emergence of adult wasps. This demonstrates it is not necessary to leave the cocoon-laden caterpillars on the plants:

Cheers

PC

Wow.......great info PC! The times I've had hornworms, they only seemed to consume the leaves and left the fruit alone. I would usually just pick them off and move them to some bushes.

Honestly, I'm not sure who to root for, since I love sphinx moths. If they're not hurting too much of a plant, I let them be and keep my eye on them. Funny how they hiss when you pick them up. Very interesting little beings......as are the braconid wasps. Ain't nature grand?!

I don't find them up here on the hill but when I used to grow a lot of tomatoes I would go out early every morning and pick them off. The cats would follow me around and eat them. What a pop sound when they crunched them. Yum yummy

I pull the infected hornworms off, but I don't kill them. Like catherinet, I just take them to the other side of the yard and toss 'em into the bushes.

The hornworms I had this year were of the tobacco variety, and along with leaves, they did munch on the tomatoes themselves.

PC: That is fascinating information. Not sure if I can think about it too much without getting grossed out though. Hornworms already have grossed me out on so many levels, but I've continued to take a deep breath and remove them when needed. Haven't even resorted to the long tongs I've seen some people use. Just a quick grab, drop, and squish move.

Catherinet: A few years back I had a person ask me to save hornworms I removed from tomato plants and call them. They wanted to pick them up and raise them to adult moths. I think I gave them one "picking" of several caterpillars but never heard how successful they were in rearing them.

Peter, that's been my experience too ... but no matter what I get nervous about seeing these on my tomato plants and remove them ... if I'm lucky to get waspson a hornworm on a leaf I duct tape the leaf inside a convenient nearby shrub!

Catherine, yes! nature is so grand, cool and awesome. When the hornworm throws a defensive hissy-fit, the noise is not all it does. The noise itself is like a lion's roar that is as loud as a jet engine a couple hundred feet away to the predator, when the macro world attacker gets within a 1/4 inch of the caterpillar's head. The sound is made by grinding (grating) its teeth. But the caterpillar usually thrashes around to direct the sound too in various directions like using a megaphone.

Humans really don't hear much of the hiss, but that's only because the majority of the volume is ultrasound which cats, rodents, lizards, other predatory insects (perhaps including ants), small mammals like rodents, spiders, possibly some birds: the ultrasound is concentrated in the most sensitive range of their hearing for them which is inaudible for us. It's an interesting practice, since some adult Sphingids (generally, the family of hawk moths) do the
same thing to confuse bats by making similar sounds with their genitals. The hornworm will also vomit a selectively digested liquid if under further assault while chattering. He then will eat it back up, just as he does his shed skins as he grows.

This fluid is similar in function to the one as Stink Bugs, and is likely rich in alkaloids like nicotine it concentrates from tomatoes. Tomatoes are addictive LOL :-) and contain nicotine, especially green ones. Nicotine is a natural pesticide not only produced in tobacco. To put it in perspective, a couple of ripe beefsteak tomatoes gives as much nicotine in our diet as 1/20 of one puff on a cigarette. Other alkaloids not as well studied probably are more prevalent in the liquid when hornworms feed on tomato instead of tobacco.

naturegirl, Sphinx moths are beautiful but I feel terrorized by them when they enter my hoop house which has great acoustics for their flight buzz and when they hammer the plastic. I don't use the humane treatment of removing them from my tomatoes and putting them elsewhere, because despite what the literature currently says, they have a much wider range of host plants than is recognized.

I have no doubt they can survive on many unidentified weeds including non Solanaceous ones. In my yard they will eat the nuisance weed Florida Pusley (Richardia scabra), for example, which is a closer relative to coffee than to tomato. The thing with Sphinx moths and all Hawk Moths is that they stop pupating in the autumn and their cocoons below ground go into a sort of hibernation (diapause) until the following Spring when they will readily reintroduce themselves very, very quickly to your tomatoes.

rgreen, thanks for pointing out the difference between the two species of hornworms. All of mine are technically Tobacco Hornworms which are larvae of the species that is the adult Sphinx Moth. Never seen a true Tomato Hornworm here, which are larvae of Five-spotted Hawk Moths. They are similar enough to mostly generalize I hope, but may have some interesting differences, especially in how they concentrate plant chemicals.

Tomato Hornworm:

GU citation (c) Whitney Cranshaw, Colorado State University, Bugwood.org:

Tobacco Hornworm (GU George Bredehoft, filed incorrectly now in Wikipedia as Tomato Hornworm):

Cheers

PC

PC, I feel equally educated and disgusted. Thanks, LOL.

"I feel equally educated and disgusted. Thanks, LOL."

Grace, for goodness' sake :-), you've inspired another post :-)

Peter's post of what he learned to share with everyone else was really educational, as
I'm sure many will end up in this thread when freaked out with seeing a Braconid parasitized hornworm on their tomatoes and have the wrong
impression to destroy it. LOL!

I just put the ewww inhibition aside, even though I have yet to put any of this stuff near my thoughts of umami, and have fun learning about the pests' and beneficials' behavior ... so we can use it to optimally control significant destructive pests like hornworms!

Rather than running in disgust, Peter now has an established bunch of wasps policing his tomatoes for hornworms and they will likely overwinter too and be back to help next time before the hornworms are able to do much :-) That's so great!

How better to design an environmentally friendly integrated pest management program and potentially could save using pesticides ... even if you are only using something as organic as Bt (Dipel)? That's what we humans do to these caterpillars when we don't cut them in half with scissors or step on them, or feed them to our cats and other wilder beasts - a job that someone has to do sometimes if they want tomatoes.

Bt organic pesticide can be used but if hornworms are the only problem, it's not that effective unless regularly applied and timed to catch the small, young hornworms. Bt is every bit, and then some, as disgusting and cruel. It is a crystallized protein produced by the infectious bacterium Bacillus thuringiensis. The hornworm eats it off the plant and the crystal becomes soluble and travels to its intestine. There, it binds and interacts with special cells in the lining and forces open pores so the intestinal contents, as well as their pH, flow into the rest of the caterpillar, digestive juices, flora and all. You can imagine, especially when it is not enough to kill the caterpillar. At least the wasps use anestesia and a neurotoxin (and the symbiotic virus) to completely numb the caterpillar, like going to the nurse's or dentist's office. Here is an absolutely awesome photograph (c) by Alex Wild I would love to post, but due to his terms of use not allowing educational content on sites with terms of use like Houzz, you need to click on it. Please do ... it is interesting and nothing ick about it:

Small Braconid wasp injecting eggs in Tobacco Hornworm (link)

About that icky factor, other cultures, such as in Africa (general source of protein), Italy (kids eating caterpillar guts "el miel" as sweets), and Korea (steamed beondegi (Korean for pupae) of silkworms are a popular street snack) have more tolerance than generally our Western phobias. My favorite example of all is the Asian sensation, which is now endangering (!!!) a fungus and even Ghost Moths in Tibet/Nepal/Western China. It's very popular in Japan and China as a medicinal herb to cure everything.

The Asian fungus I mean is deposited on the skin of Ghost Moth caterpillars after they eat certain plant roots during the growing season. The caterpillar (not a pupa) begins to hibernate underground in winter, and the fungus recognizes the chemical changes on the skin and spores germinate, infecting through pores. The fungus grows and branches throughout the caterpillar which orients itself head vertically, head up, as if trying to surface. But the fungus takes over and kills the caterpillar, which it mummifies. In Spring, the fungus sprouts a stroma through the caterpillars head, sending up a long stalk reaching well above ground. Digging up the "yarsa" fungus/caterpillar ("chong cao" in Chinese), and abbreviation for winter worm, summer grass) in the high plateau is very lucrative and because of it some lands and access (e.g. 10:35) played a role in the recent civil war in Nepal that has destabilized that country.

Back to final staged sized hornworms. Here is a popular thread from an adventurous GW member after being frustrated by (Tobacco) hornworms. It blurs the line between fascination and ewww in an attractive manner, well, don't worry, you and I can pass on trying it, but must admit this is beautiful presentation :-) If anyone tried this, I would definitely only use big fat actively leaf eating caterpillars over ~3 inches long with skin that seemed plump and not with telltale signs of something teeming underneath, just in case one had wasps inside :-P :-P

Hornworms and Green tomatoes, by Jazmyn's Mom (link)

Cheers

PC

Thanks for sharing your wisdom PC!

"Thanks for sharing your wisdom"

LOL! I just edited and included reference links to give the real folks the credit they deserve :-)

Cheers!

PC

Oh, baby Jesus, that thread.....NO, NO, NO!!!

My work is to eat and I've had some very grotesque things. And that, PC, is where I draw the line!!!!

Fascinating and gross. Thanks.

" ... that thread.....NO, NO, NO!!!"

Fair enough! That thread sure did get under the skin of some elite eaters :-). People, here in the US and other such places, myself included, are so strange to eat shrimp, which feed on detritus and scavenge bacteria and worms yet get bent out of shape about other arthropods like tomato-fed insects.

Someone had to be the first person to stick crustaceans in their mouth, or land mollusks like escargot, or ones from the sea like live raw oysters. Then to share the "nouvelle cuisine" and then have it catch on virally like sushi or sashimi which 35 years ago would have creeped-out 99% of the population. I say more power to whoever isn't affected by these arbitrary taboos. Authentic birds' nest soup or dalkttongjip or living spoon worms, who could have even contemplated eating those?

It is explained by "food porn" IMO. The antonym of which is disgust that has no rational basis and can just be fads in the modern world, with a blurred line between what's hip for an epicurean palate and what's not cool. Special preparation and/or photography make things look beautiful :-). Looks are everything in some cultures, this being especially one of them. Jazmynsmom's post hit a nerve because of that.

Grace, I'll prepay you one of these special Oreo Mud Pie Milkshakes if you promise to drink it next time you're in the Milpitas area at the local Wayback Burgers joint. They've caused quite a sensation nationally, and body builders have taken notice, among others that are nutritionally conscious. 96 crickets in the large shake and 52 bugs in the junior size. There's no doubt in my mind that in a few years insects will be on the US frontier of food farming opportunities ... if they aren't already there!

Shredded carrots, for example usually contain 1000 - 2000 insect filth
parts per ounce. Nobody I know who eats fresh cole slaw is complaining... Now to cook me up some delicious stir-fried shrimp, with slices of home-grown tomatoes & basils. I only cook tomatoes like these when stink bugs go to town discoloring them. Yuk!

Cheers and my apologies for the somewhat off topic straying! To get back on topic: Bt usage has no effect on Braconid wasp larvae life cycles. It can be used to control caterpillars and by the time the hornworms are big enough to be parasitized by the mother wasp, at that size even the hornworm itself is probably too big to even be killed with consumer Bt pesticide applications.

PC

I would just get rid of them as soon as I find them. The wasps might be too late.As gardeners we have to battle various pests. It is a game of survival. No feeling of animosity towards anything.

Sey

"I would just get rid of them as soon as I find them. The wasps might be too late."

I half agree with this. Half because if you are tirelessly diligent, you can do better than the wasps. It's best just to demystify what's going on by understanding the hornworm larval cycle, and your own practices so you can make your own decisions to choose your poison:

Larvae hatch in less than 5 days after the Sphinx/Hawk moth parasitizes your tomato plants with her eggs. The hornworm normally has 5 stages, called instars, which can last in total as long as three weeks after they hatch. A *single* healthy hornworm can eat up to about half of a Rutgers' size tomato plant including growing tips, though if it eats the fruit, less foliage is affected, which is better news earlier in the season, but psychologically it seems worse. Based on that the eating habits of the hornworm are:

(up to one inch) = 11 days ... 1st, 2nd, 3rd stage. Eats total = 2% of a plant.

(2 inches) = 3-4 days + 1-2 days' rest after. Eats total = 3% of a plant.

(over 3 inches) 4-5 days + 2-5 days' wandering after. Eats total = 45% of a plant.

The wasp can parasitize the caterpillar by injecting egg into it at any time commonly from stage 2-5. If you have wasps established, typically multiple wasps will parasitize any hornworms they can find, and they will coexist and emerge visibly at different times starting at an early caterpillar stage (usually 2-3). You can't really tell which caterpillar is infected as it goes through its normal stages with the wasp load and will feed normally ... or even more since the wasp larva control its metabolism to a degree and determine how much it eats to support both them and their host, and also how long they let the host continue actively eating.

This means, any caterpillar that has wasp pupae hanging off it has eaten your plants according to the above appetite. But next generation, there will be no Sphinx moth pupae to emerge or overwinter, or those that do will be knocked out in their first generation. If you are out there every day of the season it is a calculation you just need to consider. However, if you see wasp pupae on your hornworm, basically all the tomato damage is done, you have paid for the wasps with your tomato plants just as if they were a single Sphinx moth, but there will be no moth, just over 100 wasps emerging from its near corpse to police, serve and protect, at no additional cost to you and your tomatoes, and they will be back next season if you're kind to them.

On the other hand, if your neighbor (or a neighbor's vacant lot) is rearing Sphinx moths and releasing them, you are pretty much, screwed... the root of the pest is elsewhere and beyond your control. But your deputized wasps will go hunt them down if it is just an empty lot or field, and break the life cycle :-)

One thing that can be done, thinking about this life cycle. You can remove the large caterpillars which are usually found too late (5th instar), and rather than killing them, just stick them in a bottle (or be more formal and use a tank as in this video) with host plant (pinched off suckers, damaged tomato, broken leaves, etc.) and see if the wasps emerge in the first few days rather than it wandering, and if there are wasps, just put it outside near the tomatoes and duct tape the caterpillar with pupae hidden inside a nearby bush.

Cheers

PC

PC, I am always and eternally grateful to the person who first put oyster, lobsters and clams in their mouths. The world is indebted to them.

I will also eat (enjoy?) or at the very least TRY/TASTE virtually everything, and being Korean, you bet bbun-daegi, too, though I can't say I've really enjoyed it since the day I actually learned what they were. In fact, I've only had it once more a few years ago in Seoul--and yea, it's just totally not necessary for me to eat that. LOL

It can be alive and squirming, and I simply do not care as long as it tastes good:

Live Squid -- YUM!

Fermented? No problem.
Rotted? OK...if you didn't drop dead, I can try it, too. (I don't have to like it though...)

However, I draw the line at two things: whatever that is blinking and/or screaming at me while it's served (NO, NO, NO!), and INSECTS.

Absolutely not. Until there are no more cows, pigs, fish, kangaroos, alligators and chicken (or even snakes...or anything!) in the world, there's just no logical reason that anyone should eat a hornworm.

There just isn't. I could have had Andrew Zimmern's job if not for the fact that I cannot, will not, flat out refuse to eat insects. NO, NO, NO!

Granted, this was the first year I saw one--and a huge one, at that--and I've discovered smaller ones since then. My stomach lining could be stuck to my spine from hunger, and I'd munch on concrete before this. NO, NO, NO.

And if crickets held the secret to eternal life, I'll just go early. Eternal youth? Well....I might begin to think about it (though I think I might actually opt for old instead), but so far, nobody has claimed that, thank goodness.

That said, I do enjoy escargot every once in awhile, but I like to tell myself they're buttery meat just shaped like snails. LOL

"Fermented? No problem.
Rotted? OK...if you didn't drop dead, I can try it, too. (I don't have to like it though...) ...

... And if crickets held the secret to eternal life, I'll just go early. Eternal youth?"

I'm not planning to drop dead anytime soon Grace jeje! But Andrew Zimmern did like the taste of hákarl, so I'm waiting to see your opinion on its taste: "That's serious food. You don't want to mess with that. That's not for
beginners."

How someone can eat that stuff and not like insects which they eat every day is another of those things that doesn't have logic as part of the formula. Men seem to require much less than a promise of eternal life in exchange for eating creepy things but that's another story... Babies love insects and regularly put them in their mouths (video), demonstrating to me that insects are more likely natural sources of food and definitely nothing repulsive. Kids are at the transition and still enjoy them (video) before getting brainwashed into current norms.

The baby octopus looks delicious, and it is definitely an adventurous food here in the US where we eat other things not fit for a cockroach.

I wouldn't anthropomorphize too much about screaming; there is little purpose to screaming underwater in the octopus's habitat, where higher-pitched sound doesn't travel far enough to be efficient for SHOUTING! Octopuses SHOUT by changing color and moving their tentacles into frightened poses. (And bloggers shout by using caps and it scares me!) The octopus's brain is distributed in a very different profile than our own, so each tentacle is part of the brain or sometimes considered separate brains, complete with some memory and independent functionality. When you want to see an octopus or other Cephalopod screaming, just look for writhing movements and color change, such as in this linked video, especially at the time the tentacles are severed by the knife.

I don't subscribe to the end of the world scenario either that says we will be forced to eat caterpillars and other insects (video) - I believe the opposite. It will come as a gradually accelerating change. It's just the way our culture has become and if there is an underlying merit to something like better nutrition or economy, it will happen here, even if the older generation has to die off first, which is unsettling to many but just the nth iteration of our ever evolving culinary history - not too long ago over three generations tomatoes went from near obscurity and ornamental use to a staple part of the diet. If anyone thinks like me in the popular press, after you remove the fluff and journalistic hyperbole, that person would be scientific minded author of "Tasty", John McQuaid (link):

"“Deliciousness and disgust are very closely related - one can quickly
change into another depending on where you are or who are with. If
you want to introduce new ideas for a mass audience you have to be
careful not to up-end everyone’s expectations or override existing
trends."

So, I could never jamas tell people about what's good for them to eat and what's not :-) I won't tell you to stop putting insects on your lips for red lipstick, not to have tried Starbuck's Strawberry Frappuccino, nor apples usually shellacked with wax made from insects, nor to quit eating my favorite honey-chicken coated with insect digestive juices, Larvets or Crick-ettes (link), or even kimchee which I happen to love myself (what would I do without my Lactobacillus kimchii), etc... Tomato-born and bred hornworms seem innocuous after thinking about this!

Cheers To Thor, son of Odin! (as cricket-eating immortals, we're gonna miss you!)

PC

PC writes:

"Tomato-born and bred hornworms seem innocuous after thinking about this!"

NOPE. LOL

I found this guy in the garden this morning. I've luckily not seen any signs of damage to plants from munching but this thing was huge and gnarly. I would have thought it was a tomato hornworm but thanks to this thread I know better.

I did not find hornworms until yesterday! 2 of them, but with white eggs on, I guess I don't need do anything.

It's tough being a hornworm!

"It's tough being a hornworm!"

No argument there -- but even hornworms have it easier than a Cabbage butterfly larva (e.g., Pieris brassicae), infected by another Braconid wasp, Cotesia glomerata. (Cotesia congregata is the hornworm wasp.)

Not only does the C. glomerata do the same thing as the hornworm wasps but to the Cabbage larvae ... When it is done emerging, they instead migrate onto foliage into a pile and pupate. Instead of letting the Cabbage butterfly caterpillar go into suspended animation, they de-zombify the caterpillar after they are safely emerged and spun, and control the caterpillar's mind to have the caterpillar spin its cocoon, but for the wasps.

The new exterior cocoon is formed over the pile of little wasp cocoons, to better protect them as a second layer. Then, the hapless caterpillar is not yet done. It is further controlled to rear up and be a security guard for the metamorphosing wasps, so if any more "hyperparasitoid" wasps come along, or hungry ants, it will flick them away with its head like a bouncer at the door of a club. The caterpillar eventually dies after it's guard duty is finished and the wasps fly away metamorphosed from their cocoons.

Similar wasps can actually parasitize the the Braconid wasp emerged larvae and cocoons in much the same way, so they are by no means safe! It's a dog eat dog world out there! Or a cat eat cat world!!!

Here's a video with great photographic effects to demystify the unbelievable zombie mind control. I don't think anyone knows exactly how the mind alteration is accomplished even though the video makes a claim, but the two main ideas are that the symbiotic virus the mother wasp originally injected somehow does it finally getting into the cat's brain, but another idea with support is that a couple of wasp larvae stay behind self-sacrificing themselves and actually drive the caterpillar like the Martian creatures did in the War of the Worlds ... or Tony Stark in his Iron Man suit, or my favorite of all who must have gotten this idea from the wasps, Simon Bar Sinister (link) with his caterpillar in a dog eat cat eat dog world :-). Same genus of wasp, sister species, the only thing that changes is this cat is a bad Brassica pest:

Cheers

PC

Nah, nature just is what it is... if we aren't careful, we anthropomorphize what we see. Cruelty is only a trait of creatures which must have right and wrong socialized into their behavior. It embodies the very definition of anti-social action. Insects have little-to-no capacity for cruelty. We just need to understand how nature works.

We all know this, but the subject - especially to gardeners - is fascinating... Insects are voracious. Individual species have no understanding, for example, of population control. If one species did not consume another, a single species of insects would multiply and devastate the environment. In many cases, separate aspects of the natural world must be looked at as a whole.

Suffering is suffering... no need to anthropomorphize, understanding of suffering is not a prerequisite to suffer, i.e. from fear and pain. Anyone who has ever owned a dog knows that animals are capable of a large range of emotions, even if they aren't capable of understanding them. Insects may or may not actually suffer, but most higher animals sure do. And I think it that makes nature itself quite cruel. Not the wasp that doesn't understand its actions.

I understand what you are saying, suffering is definitely rife in the natural world, but the cruelty which causes suffering is mainly a human trait. Some may see it as semantics, but I would argue that while nature may seem severe at times, it's not 'cruel'.

The wasp has no willingness to do anything but survive. It does not enjoy the suffering of the 'worm'. It is only acting on an instinct. There is no cruelty. The infliction of pain does not indicate cruelty.

Again, I know it seems like semantics, but instead of looking 'down' from a human perspective, let's look at it sideways from the plant's viewpoint... if left unchecked, the worms would destroy the plant. Is that cruel? To the plant, and the entirety of that species, the wasp is a savior. It is the worm that would, unchecked, - and borrowing what I claim as the misnomer - 'cruelly' destroy every plant of the species.

I know it seems harsh, but there is neither cruelty, nor malice. It just is what it is...

Anyway, I hope there is no hard feelings, this is largely just different perspectives over definitions and applications of meanings... semantics.

But it is, to me, an interesting subject.

Why would there be hard feelings? We are just having a friendly conversation.

I guess calling nature cruel is anthropomorphizing nature itself.

I agree Peter. As far as hard feelings... sometimes written discussions carry the passions of our convictions, but unfortunately, do not always carry the fellow feelings of comradery and friendship. It is also my writing voice that some people find objectionable. Who knows lol, maybe it's me they find objectionable. ;-)

"The wasp has no willingness to do anything but survive. It does not
enjoy the suffering of the 'worm'. It is only acting on an instinct.
There is no cruelty. The infliction of pain does not indicate cruelty."

I have become more liberal in the interpretation and think it is too black and white as well. It is Mark Twain's sort of approach: in What is Man? Man's Place in the Animal World:

"Of all the animals, man is the only one that is cruel. He is the only one that inflicts pain for the pleasure of doing it.”

In a semantic discussion, the difference usually made is between a sadistic-human and a sanguinary-nature organism. Where this entire argument falls on its face is that to make a clear distinction, different species would need to experience the emotional state of organisms of different species. So far, this simply has not been solved/studied enough and it is mainly based on an anthropocentric view of the world. The fallacy is the a human bias scientifically called "splitting", and commonly, black-and-white thinking.

I'm inclined to think that this is just another of many generalizations humans make and there are equal disagreements as anthropomorphizing as about zoomorphizing human actions to essentially excuse us from being cruel, when it is related to eating. For example, the way the octopus was sliced up live to eat in a previous post.

The consolation is that as developing powerful brain scanning techniques and the understanding of neurology blossoms, it will be easy soon to see, for example and perhaps, the pleasure centers of a cat's brain lighting up as it tortures its prey. Or a squirrel's when it teases us and enslaves us without mercy to finally dip into our harvest!

As to whether a wasp larva experiences pleasure at slicing apart its infected hosting caterpillar, I couldn't judge its emotional state but I'd put money on its brain's pleasure centers lighting up like a Christmas tree with each slice it takes, and doubly so with each more effective tear and rip.

Cheers

PC

I know I'm about 4 years late to this discussion, but good god, that was an interesting read. PC, if you wrote a book, I'd read it.

On a tomato plant, I found several already parasitized hornworms. As the caterpillar was no longer eating, posing no threat and I welcome additional braconid wasp as allies, I left them where and as they were.

The next day, a few were missing; I assume eaten by birds, attacked by other larger (paper) wasps or other predators. I found none on the ground. Do the caterpillars eventually drop from the branch once the feasting has concluded?

I would like the cycle to run its course to completion without any further interference & have the braconid wasps hatch. I’ve considered putting the remaining caterpillars into a container covered with a mesh fine enough to protect them from other predators & hyperparasitoids but loose enough to allow airflow and the exit of the newly hatched wasps. Does this sound reasonable? Does anyone else here use a a better way to raise, encourage, assist, protect the braconids?

I went ahead and did it:

- Small opaque-ish plastic container w/ top cut off

- inserted 4 tomato plant branches w/ caterpillar & wasp cocoons attached

- plastic mesh onion sack rubber-banded over the opening

- left it at the base of the same plant

I'll try to update changes/results in case anyone is interested