1. The Primary Melacha that was in the Tabernacle-Slaughtering: 
2. The Biblical Prohibitions included in the above principal Melacha:
A. Killing in forms other than slaughtering:
Not only is slaughtering [included in this principal prohibition] but [also] anyone who takes the soul from any species of animal, bird, fish, and rodent, whether [he did so] by slaughtering it [and] whether by tearing it [open, and] whether by hitting it, he is liable.
Strangling: One who strangles a creature until it dies is [transgressing] an offshoot of [the prohibited action of] slaughtering. [As will be explained in Halacha 5 regarding removing fish from water to the point that it can no longer live.]
B. Injuring a creature:
Causing a creature to bleed: The taking of life [prohibition] which one is liable for, is not only when one removes the entire life-force from the creature [i.e. kills it], rather even if one removed [only] a part of its life-force he is liable. For example one who [injures an animal to the point that he] takes out blood from one of the limbs of the creature then he is liable for taking out life from that area being that blood contains [ones life-force which is] the soul.
Causing a bruise to a creature:
[Furthermore he is] not only [held liable] if blood actually comes out [of its skin], but even if one bruised one of the creatures limbs to the point that blood [vessels have been broken and] gathered under the skin [thus causing a “black and blue mark”] then even though [the blood] has not gone out [of the skin] he is liable being that it is a bruise which will never be replaced. As once the blood [vessels have been broken and] gathered under the skin it can never return back to its place, and its only that the skin is preventing it from going out, and he is thus liable for taking out the blood of that area.
Bruising an animal and the like: [However] the above only applies to a bruise made in a person or domestic and wild animal or bird or in [any of] the eight rodents mentioned in the Torah (in Parshas Shemini) which are the weasel, the mouse [the toad, the porcupine or hedgehog, the lizard, the snail, and the mole] of which each one of these has skin which prevents the blood from going out.
Bruising an insect: However one who bruises other creeping creatures and insects is not liable until he removes blood from them. However if the blood gathered [in its body] and did not leave, then this is a [type of] bruise which will [have the blood] return back to its place, as if the blood had left its area then it would have came out being that it has no skin preventing it.
C. Killing or injuring not for a use of the creature itself:
Killing for self use: It was already explained in chapter 278 [Halacha 1-2] that there are opinions which say that a Biblical [Shabbos] prohibition only applies if the [forbidden] action was done for its own need, meaning that one needs the actual item to which the action was done to.
What is considered a self use? Therefore one who removes the life [of a creature] is only liable if he has a need for the body of the creature which had its life-force removed from, or [if he needs] its skin, or he needs the soul which he took out from it, meaning the blood that has left it in order to give it to his dog, or if he bruises a person which is his enemy and he thus desires for blood to come out from him so that he witness revenge on his foes (see Choshen Mishpat chapter 424 [Halacha 2]). However one who kills a snake in order to prevent it from injuring him then this is an action done which is not self needed being that he does not need either the body of the snake or its blood and he is only killing it in order to be saved from injury.
D. The killing of creatures which do not reproduce-Fleas and Lice:
One is only liable for removing life-force on species of creatures which reproduce and are created through [the union of] a male and female, [as will be explained below in Halacha 4]. Nevertheless [killing] the flea contains the [Biblical prohibition] of taking a life even though it is created from earth and does not reproduce, because all [creatures] that are created from earth have vitality as if they were created from male and female, as initially all creatures were created from earth as it says [in the Torah] “And G-d said let the earth extract etc.”.
Summary of the Biblical prohibition of killing a creature:
It is a Biblical prohibition to kill or remove blood from any creature. Included in this is strangling a creature, such as taking a fish out of the water to the point that it can no longer live.
However it is only Biblically prohibited to do the above if:
- The creature was killed or bruised in order to use its body for a certain purpose, such as to eat or for its skin and the like. [or if one casually killed it and it is a type of creature which is generally killed for the above purpose].And
- The creature reproduces and is thus not a spontaneous generation, with exception to if it is created from earth in which case it too is included in the Biblical prohibition.
May one cause a bruise [black and blue mark] to a creature?
Any creature which has skin, which includes all animals, and birds, one is Biblically liable for forming a bruise on them. However by creeping creatures and insects which do not have skin one is not liable until blood actually leaves there body.
3. The Rabbinical prohibition
Rabinically forbidden to kill even not for a self use: Any [forbidden] action which is not done for self use is despite not being liable on, is Rabbinically forbidden [with exception to when done to prevent danger as will be explained].
Summary-The Rabbinical prohibition:
It is Rabinically prohibited to kill or injure a creature when done not in order to use its body or blood.
4. The killing of creatures which do not reproduce-Fleas and Lice:
One is only liable for removing life-force on species of creatures which reproduce and are created through [the union of] a male and female, however insects which are created from [the bacteria found in] feces and from spoiled fruits and the like, such as for example worms [that grow] in flesh and like [the] worms which are found in legumes, then one who kills them exempt [from liability].
The reason for this is: because in the Tabernacle the taking of a life was only done to rams, techashim and chalozon which are [creatures] that reproduce and are born from a [union of] male and female.
Killing creatures which are created from earth: Nevertheless [killing] the flea contains the [Biblical prohibition] of taking a life even though it is created from earth and does not reproduce, because all [creatures] that are created from earth have vitality as if they were created from male and female, as initially all creatures were created from earth as it says [in the Torah] “And G-d said let the earth extract etc.”.
Killing lice: What is considered a flea? This is a black insect which jumps. However the white insect that crawls is called a lice and is permitted to kill it on Shabbos being that it is [created] from sweat.
Killing lice when checking ones clothing for them: However this [allowance] only refers to when one happens to find a lice on his flesh or [happens to] find it on his clothes. However one who is [in the process of] cleaning his clothing of lice then he may [only] squeeze them with his fingers [without killing them] and throw them (even into water). However it is forbidden to kill it with his hands as since he is cleaning his clothing of lice we suspect that he may come to also find fleas and also kill them.
Killing lice when checking ones hair for them: However when checking ones head [for lice] it is permitted for him to kill the lice with his hands being that flees are not commonly found on one’s head.
Removing lice from skins: One may not remove lice form the skins of fox and the like being that [in the process] one removes hair from the skin which contains the sheering prohibition, and although it is done unintentionally, nevertheless it is an inevitable occurrence [and is thus forbidden].
The general rule: It is only Biblically forbidden to kill creatures which were born from a male and female union, or which were spontaneously created from earth such as fleas. However killing a spontaneous creation not created from earth does not contain a Biblical prohibition [However regarding if doing so contains a Rabbinical prohibition, see Q&A.]
May one kill lice? Yes as lice reproduce through sweat and not through male and female union. [See Q&A 3]
May one check someone’s hair for lice on Shabbos? Yes, and one may also kill them in the process. [However he may not do so using a lice comb being that it pulls out hair in the process.]
May one check clothing for lice on Shabbos? Yes, although he may not kill them with his hands upon doing so. As well, it is Biblically forbidden to remove lice from animal skins.
May one kill fleas? No, as they are created from earth which has the equivalent life-force to having been created through a male and female.
May one kill worms that grow in meat and inside legumes? One is not Biblically liable for doing so [although it is Rabbinically forbidden to do so according to some opinions as will be explained below in the Q&A.]
May one today kill lice even though we see with our own eyes that it lays eggs?
The vast majority of Halachic authorities, including the Lubavitcher Rebbe, rule that the laws of the Torah are not negotiable, and thus once the ruling has been given that lice are permitted be killed being that they are born from sweat, this is the final ruling both for leniency and stringency irrelevant to what scientists and biologists may say.
May one kill insects that were created from rotting fruits and meat?
Although doing so does not contain a Biblical prohibition as stated above, there is discussion as to whether it contains a Rabbinical prohibition. Some Poskim rule that doing so is permitted, just like lice. Others rule that it is Rabbinically forbidden, and so is implied from Admur.
May one kill insects that have grown within fruits prior to them having spoiled?
If they grew on the fruits while attached to the tree then it is forbidden to kill them. Others go on to further say that even if they grew when detached, but prior to spoilage of the fruit, they are forbidden to be killed. It is possible to learn this way in Admur as well.
5. Removing a fish from water:
One who strangles a creature until it dies is [transgressing] an offshoot of [the prohibited action of] slaughtering.
Therefore if one took a fish out of a bucket of water, and left it [outside the water] until it died then he is liable for strangulation. [To be liable] one does not have to [leave it out] until it completely dies but rather as soon as it [is left out to the point that] the width of a “Sela” of it has become dry between its fins, then one is liable even if he returns afterwards back into the water, as [once it has been left out for this long] it is no longer able to live. [Furthermore, to be liable one does] not [have to leave it out] until it actually dries but rather even if [it has been left out to the point that] when one touches it with a finger mucus comes out from it and gets pulled out with the finger [he is liable].
Asking a gentile to remove a fish from water: Therefore one must be careful to not tell a gentile to take out a fish from a barrel of water even if he fears that it will die there [in the water, and thus contaminate the water and cause him a loss ].
Removing a fish from a river or pool of water: All the above is referring to when he took out the fish from an area that it was already trapped in and was not lacking any further trapping at all, such as for example [the fish was in a] bucket or barrel (see chapter 497[Halacha 1]). However if one took it out from an area where it was lacking further trapping, such as for example [taking a fish out from] a river or pool, then even if he immediately returned it into water that is in a vessel, [nevertheless] he is liable for trapping. [Furthermore] even if one did not catch it with his hand at all, but rather simply draw it out of the river with a bucket of water, then he is liable for trapping as when [the fish] is inside a bucket it does not lack any further trapping.
It is a Biblical prohibition to strange a creature, such as taking a fish out of the water to the point that it can no longer live.
May one ask a gentile to remove a fish for him from a bucket of water?
6. Killing dangerous animals and creatures:
A. Creatures that definitily have a deadly bite or sting:
Any wild animal and crawling creature which bites and definitively kills, such as a lethally venomous snakes and a rabid dog and the like of other dangerous creatures which have a definite deadly bite, then it is allowed to kill them on Shabbos even if they are not chasing after one at all.
The reason for this is: because there is danger of life involved [in refraining from] killing them as they may [come to] kill a Jew, and [the rule is that whenever there is] any possibility [that a] life [will be endangered] then it pushes off Shabbos, [and allows one to do] even a complete Biblically [forbidden] action even according to those opinions which say that even an action which is not done for its own use one is Biblically liable on.
B. Creatures which are not deadly but cause bodily injury [in contrast to mere pain]:
If the creature is chasing oneself: Other dangerous creatures, even those which definitily do not kill with their bite but rather only damage the body, such as snakes and scorpions in areas that they never kill with their bite [or sting] and rather only damage, and so too any creature of the like, then there are opinions that say that if [these creatures] are running after oneself then it is permitted to kill them according to those who say that any action which done not for its own use is only Rabinically forbidden. [Regarding insects and the like which only cause mere pain-see next Halacha 7-9!]
Their reasoning is: because in a situation that involves bodily injury the [Sages] did not decree [against doing a Rabbinically forbidden action, which includes any action that is not done for its own use].
This case is not similar to the [case of the] flea which is in the midst of stinging ones flesh in which case it is forbidden to kill it, [as] the flea does not cause injury to the body but rather pain alone.
If these creatures are not chasing oneself: However if [these creatures] are not currently chasing after oneself and it is only that one is worried [that they may do so] in the future, then it is forbidden to kill them in a way that it is blatantly obvious that it was intentionally done. However it is permitted to trample on it while in the midst of casually walking even if he has intention in doing so in order to kill it, as long as he makes it appear as if he is casually walking and does not intend at all to kill it.
The reason for this is: because since an action which is not done for its own use is only Rabinically forbidden [therefore it is not forbidden in this case as] the [Sages] did not decree at all against [doing an action even when not for its own use] in a case that involves bodily damage even if there is only mere doubt [as to whether bodily damage will occur]. However in this case [that they are not chasing oneself] one needs to alter his method of killing them as much as it is possible for him change, which means that he is to make himself appear as if he does not intend to kill them.
[However] according to those opinions which say that even an action which is not done for its own use one is [Biblically] liable on, it was only permitted to kill creatures which are chasing after oneself and to trample on [creatures] casually when they are not chasing after oneself, by those species of animals and crawling creatures which have the possibility of having a deadly bite. However a creature which never kills with its bite is forbidden to even [casually] trample on it, and even if it is running after oneself, being that one may not desecrate Shabbos with a complete Biblically [forbidden] action in order [to prevent only] bodily damage.
The Final Ruling:
The main Halachic opinion is like the former opinion, however nevertheless every meticulous person should be strict upon himself, regarding this [possible] Biblical prohibition, in a situation that it is possible [for him to refrain from killing it]. Such as if it is not running after him then he should not trample it if it is possible for him to guard himself from it and to warn others to beware of it.
C. Killing creatures which at times can be deadly and at times not that are not chasing after oneself:
Even by those species of animals and crawling creatures which carry a doubt regarding the deadliness of their bite, as at times they can kill and at times they will not kill, one must alter his method of killing them so long as they are not chasing after him. [Thus one may only kill them if they are not chasing him by stepping over them while he is casually walking as explained above in B under the first opinion.]
One may kill creatures which pose danger in the following scenarios:
- If the creature is definitely lethally dangerous, [which means that their bite always kills] then one may kill it in any form [in order to neutralize the threat], even if it is not chasing after a person.
- If the creature is not definitively lethally dangerous but at times it can be lethal and at times not then it is permitted to kill them if either a) they are chasing after oneself, or it is not chasing after oneself but b) one kills it by stepping on it in a way that he makes it appear as if he were in the midst of a casual walk, and it thus appears to the bystander that he did so unintentionally.
- Creatures which never kill but can cause bodily injury [as opposed to just mere pain] then if they are chasing after oneself may be killed in any way. If they are not chasing after oneself, then one is allowed to kill them through casually walking on them, as explained above, although with these creatures, if it is possible to guard oneself from them as well as to warn others, then every meticulous person should refrain from killing them.
In short: One may always kill a creature that is chasing after oneself if it causes bodily damage as opposed to mere pain. If it is not chasing after oneself then one is to kill it casually, with exception to a case that the creature never poses danger to life, in which case one is only to kill it if he and others cannot beware from it.
7. The prohibition to kill insects which cause mere pain even in the midst of a bite:
It is permitted to only trap a flea which is in the midst of biting oneself, however to kill it is forbidden according to all opinions even if it’s on ones flesh and is in the midst of biting him.
The reason for this is: As due to mere pain [the Sages] only permitted trapping [it] being that it is not a species which is commonly trapped and thus trapping it is not considered a [Biblically forbidden] action at all, however killing it is a complete [Biblically forbidden] action. [Now although] it is not done for its own use in which case there are opinions which say that one is exempt [from liability] on doing so, nevertheless [even according to them] it is Rabbinically forbidden and was not permitted to be done [in order] to prevent mere pain being that its prohibition is rooted in the Biblical [prohibition], meaning if [this same act] were to be done for its own use [in which case it would be Biblically forbidden].
May one squeeze the insect to weaken it? [Furthermore] even to squeeze it with ones fingers to weaken its strength so that it not return to him is forbidden because of a decree that one may come to kill it. Rather he is to take it in his hand and throw it away.
It is forbidden to squeeze an insect, even if it is in the midst of a bite, as he may come to kill it which is forbidden in all cases, even if the insect is in the midst of a sting.
8. Killing spiders:
Those people which kill spiders on Shabbos (that are called shafin) need to be rebuked being that [spiders] do not cause bodily damage, and although there is worry that it may fall into ones food [and become lethal], nevertheless [it is forbidden to kill them] as this is not common [to occur], as well as that it is possible to cover the foods, and that also it is only one in a thousand that is lethal in food, and that also even if it did carry a worry of danger [the Sages] only permitted killing it through casually trampling on it.
May one kill spiders?
No, they are not deadly and do not cause bodily harm.
May one kill a tarantula?
If they cause bodily damage then yes following the rules above. If not then no.
9. Being cautious not to trample on ants and other non-dangerous creatures:
Species of crawling creatures which do not cause injury such as ants and the like, is forbidden to trample them even if one does not intend to kill them [in doing so] but it is inevitable.
[Thus] one must beware of [stepping on] them in areas where they are commonly found.
May one step on ants while walking?
This is [Biblically] forbidden being that they will inevitably be killed, and thus one must take caution when walking near areas which he knows contains insects.
 A type of animal with a unique colored skin
 Vetzaruch Iyun as for why the Chilazon was not mentioned here, despite it being mentioned in 316/1 regarding trapping, and in 316/20 regarding learning the source that all the animals killed must be from male and female union. Perhaps though one can say that only those animals which are actually slaughtered are considered a Melacha in the legal sense, as an action must be done to actually kill them. This is in contrast to a fish which merely needs to be removed from the water, and no action of killing need be done.
 Mishneh Berurah 316/32 explains that since their skin is soft like flesh therefore their blood vessels that have broken are quickly returned to their place. Thus according to this explanation they do have skin, and it’s just a matter of whether their skin is soft or hard.
 There it explains that one who injures a person on Shabbos is exempt from paying damages being that he is liable for death.
 The Mishneh Berurah adds the following: a) It is nevertheless Rabbinically forbidden [unlike the opinion of the Magid Mishneh brought in the Magen Avraham which holds here that it is completely permitted] and it is only by lice that the Sages completely permitted killing it because it was created from sweat or because it is repugnant.] b) It is only Biblically permitted if it grows while off the tree and after the food has spoiled. However if it grew while on the tree or before the food has spoiled then it is included in the Biblical prohibition.[See Mishneh Berurah and Biur Halacha on Halacha 9] See Q&A below
 Rav Dessler in Michtav Eliyahu vol. 4 page 355, Opinion of Rav Yehuda Bril brought in Pachad Yitzchak “Tzeida”, and many other Poskim listed in Yalkut Yosef Vol. 4 chapter 316.
 Brought in Sharreiy Emunah chapter 43
There the Rebbe states the following rules regarding scientific studies that contradict the teachings of Torah:
1) Science is based on theories and not facts, and thus one cannot distort or change the simple interpretation of the words of our Sages which are the words of the Living G-d which states the absolute truth, based on conclusions developed from un-provable and merely theoretical hypothesis of a human.
2) However when science has come to a conclusion based on an absolutely provable fact then within the allegorical sections of the Talmud there is room to interpret the sayings in deviation of their simple meaning.
3) However when it comes to the legal aspects of the Torah then there is no room for deviation at all from its simple meaning, irrelevant to what scientific study has proven with human intellect, and thus the Halacha is to be taken literally for all matters. Regarding this specific issue the Rebbe there states that he has thoroughly investigated the topic of spontaneous generation while in Paris with the greatest professors in this field, and although there are studies which have showed that creatures which in the past were believed to have generated spontaneously in truth were reproduced through male and female, nevertheless they have no conclusive evidence that such a concept does not exist. Furthermore there are many biologists which firmly believe that organisms can be created from inanimate items.
 Pachad Yitzchak 10 “Tzeida” p. 21; Sheivet Hakehasy, brought in Piskeiy Teshuvos 316 and Yalkut Yosef ibid,
 Authors personal thoughts:
A question on the first opinion: If science has today “proven” that lice are reproduced through male and female then why do we not simply say that this is not the species of lice referred to by the Sages, and thus there is no contradiction and it is thus forbidden to kill the species of lice that does reproduce.
A. Seemingly the answer to this question is that tradition-which is as authentic as Halacha- has it that these lice are the same lice referred to always and thus there is no room for compromise.
A question on the dissenting opinions and their scientific facts: To my knowledge studies have not proven that sweat does not take a pivotal role in the development and growth process of the egg while in the mother lice and after it has been laid. Perhaps then this is the meaning behind the saying of the Sages that the lice are created from sweat, and there is thus no proven contradiction to the saying of the Sages. If so there is no room at all to be stringent against the ruling of the Sages of all generations.
 Magen Avraham 316/20, based on Magid Mishna on Rambam 11/2
 Mishneh Berurah 316/41, based on Lechem Mishna ibid, and so is brought in Peri Megadim A”A 20.
 From fact a) omits the clear ruling of Magen Avraham that it is permitted. B) simply states that one is exempt as opposed to permitted as he writes by lice.
 Magen Avraham 316/20, however see Peri Megadim ibid that questions this saying either way it should still be permitted being that the insects were not created from the earth. However the Biur Halacha negates this proving clearly that insects which were grown within a fruit when attached are considered grown from the earth.
 Biur Halacha Leharga
 As all bugs that are created from fruit prior to deterioration are able to have offspring. [Biur Halacha ibid]
 From the fact that Admur mentions the wording of the Rambam which only mentions the allowance by spoiled fruits, and completely omits the ruling of the M”A that allows it when detached. Perhaps this is coming to teach that even when detached it is forbidden so long as the fruit has not yet spoiled.
 Meaning that it has congealed and thus sticks to the finger and gets stretched out like gum.
 Levusheiy Serud
 There it discusses when a fish is considered to be trapped.
 See Halacha 7
 Some spiders are lethal when eaten