How does one check life signs of an insect?

Suppose some insect is squashed, let's consider a spider for example; suppose it doesn't move and doesn't react to external stimuli but is still alive; the observer doesn't know this and he wants to determine for sure if the spider is still alive. How does he do this?

If you have stood on an insect you have probably killed it.

If you are not sure and it is not completely squashed then put it under jar and turn the light off, see if it moves. Insects respond to lights going on and off.

Assuming he was squashed partly enough in order for him to be in "vegetable state" and not respond to external stimuli, maybe one way of checking if he's still alive would be to see if his brain is still "on" by means of plugging electrodes to his brain; but insect brain is different from that of mammals so I'm not sure if that metric of defining alive or dead will be fruitful ( maybe some insects can live without their brains and if that's the case, a different metric has to be used to define dead or alive. This is the same as determining what makes Jellyfish alive or dead because they don't have brains ).

Movement is not necessary the greatest way to tell if insects are alive, plus you also have to define what alive is.

You can pop the head off a grasshopper and it can still do coordinated movements. If you seal the hole through the cuticle with wax (to prevent drying out), the headless grasshopper can stay alive for days.
Is it alive or dead? Different definitions will give different answers.
Many detached parts of animals can continue to twitch for a while, like legs.

You also have to decide if what you call alive is the whole organism or just some of the cells of the former organism. The cells in tissue culture derived from the deceased Henrietta Lacks could present a problem in this way.

Thanks, I thought so too. I think the definition of cells ceasing to operate in the entire body best fits in this case, take for example Planaria, a creature that if cut in half then each half will become a new Planaria. In such a case stomping on the creature probably won't kill it and really the bottom-line metric as if the creature lives or dies is if it's cells cease to function.

CGandC said:

Thanks, I thought so too. I think the definition of cells ceasing to operate in the entire body best fits in this case, take for example Planaria, a creature that if cut in half then each half will become a new Planaria. In such a case stomping on the creature probably won't kill it and really the bottom-line metric as if the creature lives or dies is if it's cells cease to function.

However, few would argue that Henrietta Lacks is still alive.

insects breath through openings on their thorax, so you could try artificial respiration - but its tricky to blow with the correct pressure

BWV said:

- but its tricky to blow with the correct pressure

Isn't it always!?

BillTre said:

However, few would argue that Henrietta Lacks is still alive.

Theoretically, is it possible to use HeLa cells to regenerate neurons? ( assuming one can control the growth rate of the HeLa cells )

I don't know much about HeLa cell lines, but they have been in culture for many years. So many cell generations have passed. In culture cells often do things like accumulating mutations. Some can be changes in numbers of different chromosomes.
Besides possible having problems in how various different cell types and developmental processes work (due to damage to genes encoding products involved in those processes, Changes in chromosomes might not work in meiotic processes, where chromosome manipulations are important.

It you tried generating neurons soon after the cells are put in tissue culture, it could work. However, the longer it is kept in culture, the more likely it will get a mutation affecting a process involved generating the cells you want.
If you took stem cells (or whatever is needed) out of yourself cultured them, turned them into some cell specific cell type, you would be doing the same kind of thing.
This is also very similar to the CAR T-cell method of treating cancer (take t-cells out of the patient, modify them genetically to antigenically activate them against the cancer cells, put them back in the patient).

This is going in a different direction than I thought. Harkening back to getting squashed: spiders flex and extend by hydraulics the pressure in their bodies. If their exoskeleton is pierced, the pressure will be lost, their legs will flex, closing them into a ball and they will be unable to move thereafter. So they're doomed to death, if not actually dead yet.

DaveC426913 said:

This is going in a different direction than I thought. Harkening back to getting squashed: spiders flex and extend by hydraulics the pressure in their bodies. If their exoskeleton is pierced, the pressure will be lost, their legs will flex, closing them into a ball and they will be unable to move thereafter. So they're doomed to death, if not actually dead yet.

Well, thinking about it the question of how to define something as "dead" can quickly fall into the realm of skepticism and the answer's difficult since there isn't any scientific consensus for it - should the question viewed microscopically , i.e. if there's still cellular activity after the creature's limb movements have ceased to be active ( but what if the creature's paralyzed? ) or should it be viewed macroscopically? i.e. the creature's not moving anymore after long period of time and that's it ( what about pleco fish that can be in a period of non-motion for long period of time during dehydration period? ) or should it be somekind of a mix between the two or neither? well it doesn't really matter and in any case, the spider might be doomed to death if you managed to cut all its limbs but somehow sustain it to keep it alive ( like injecting food and water particles into his digestive system ), so don't bet if the spider's dead if a biologist wants you to put a bet on it.