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Las tarántulas y sus mitos
Enemigos de las tarántulas
Ciclo biológico y reproducción
Tarántulas mexicanas
Primeros auxilios y enfermedades
Taxonomía y anatomía de las tarántulas
Situación legal
Status de poblaciones y mercado ilegal
Diferencias entre insectos y arácnidos
Otros arácnidos
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Biologic Cycle and Reproduction


| Males | Copulation| Females |

The reproductive cycle of tarantulas is one of the most simple in the arachnid world. It is not our intention to belittle it, it is complex, but of all courtships and offspring care recorded for arachnids until now, they have the least ceremonious and most pragmatic ones.

We should mention that the following information is only based on Mexican species, since temperature and season changes in Mexico are the factors that influence our findings.


Weather the chicken or the egg came first doesn’t really matter if we don’t consider the rooster. Male tarantulas are really unsung heroes. It is amazing what they have to go through to achieve what seems to be their sole purpose in life - deposit their semen on a female.

Their perilous lives, filled with predators, begins when hatching from an egg sack, where they were alongside about 800 siblings (this number varies from 150 to 1,500). At this age, it is practically impossible to distinguish between males and females.

However, around the age of 3 years, through their exuvium (shed skin), it is possible to see the sperm sacks or spermatheca in the females’ epigynium area, and the lack thereof in the males. A little later on, and with a lot of experience, the difference in gender can be determined by their activity and character. How? Males are noticeably more active compared to the laid-back and tranquil females. Another way to determine the gender is by observing, if possible, the spinnerets in the males located over the epigynium. These glands spin the spermatic web, and they can be seen as a darker patch. Maybe at first it will be hard to find them, but once you do, this will be the easiest way to determine the gender of your tarantula, even when it is young.

As soon as they hatch, little tarantulas show a semi-social behavior. They interact with their mother for some time, usually around three weeks. After that, and for most Mexican tarantulas, they all march out single-file, bidding their mother farewell forever, severing any tie that ever existed, because, from this moment on, they represent a possible source of protein! It is worth mentioning that some species interact with their mother and other members of their species for an indefinite amount of time. In some cases, you can even find several young specimens (about two years old) still living at their mother’s home.

Once they have left the protection of their first home, each little tarantula will take a different path, finding and taking over any little crevice, and making their homes, never drifting very far from their place of birth.

The Brachypelma genus, the most common in Mexico, and the Aphonopelma are usually great gallery builders. An adult female can dig galleries over 1.30 meters deep, and I have found that they have designated areas where they eat or molt, and areas only for waste.

During this ordeal, they are exposed to a great number of enemies in search of a delectable little tarantula, and as they are very prolific, they are part of the diet of many predators.

If they manage to survive around four to six years, the big moment arrives – the moment when the male is officially declared an adult, when it reaches maturity. After surviving a long list of mishaps, the male reaches sexual maturity, and this shows in his last molting.

How can we know? It is very simple: The first pair of legs will grow a set of hooks called “tibia hooks” that will come in handy to survive what is yet to come! His pedipalps will grow a pair of hooks called “spermatic hooks” or “spermatic bulbs” which will contain the semen.

Even at an early age, males show different behavior than females. They are more active and slender than their “chubbier” sisters, and with this last molting, they are now very different. But, why do I insist this is their last molting? Well, because they will never be molting again, they only have about one year more to live, and during this time, they will only focus on reproduction, even if they lose their lives in the attempt.

Once the male is done molting and his new chitin exoskeleton is completely dry, it will begin its intense, sexual, active, short life. It will not stop moving constantly until the day it dies. It will only stop to rest briefly, or eat a snack.

One fine day it will decide to spin a “sperm web”. This web will be woven someplace where it can be perpendicular, and the tarantula will use its epigyneal spinnerets to spin it. This web is very special because it does not have capillarity, and once it is finished and shaped like half of a tent, the tarantula will go underneath it, up-side-down, and very carefully will deposit a single drop of semen on the underside. This pale white drop will remain hanging from the web, and then the male will carefully come out and climb to the top of the web.

Once he has done this, he will carefully dip his “sperm hooks” or “sperm bulbs” in the drop of semen, absorbing it into the hooks with a very careful and slow movement from the inside out, until there is not a trace of semen left. After this, the reason why is still a mystery, it will destroy this web, and will begin its great journey.

The male, loaded with semen, leaves his gallery never to return again. It will begin an amazingly active journey, and this is the reason why males are so thin. How could they survive the number of perils if they were as large in girth as their sisters? They climb, they fall, and they run all day from one place to the next in their frenzied quest to fertilize as many females as they can find, resting very little along the way. Sometimes, they will stop shortly to eat a small animal that crosses their path, but I can assure you that they will not finish it, because they become restless and leave their prey almost untouched.

In my breeding facility, we let most males roam around freely within the building so they will not get hurt inside the containers.

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Once the male is standing outside a female’s den, it is believed that he can detect pheromones that are very particular for the species, probably providing specific information of whether or not they belong to the same species, if the female is a youth or an adult, or possibly if it is a male not yet mature. These are only speculations, since this has not been fully studied, yet, but the specific behavior of a male towards a fertile female ready to be fertilized is very evident. While sometimes it will run away in fear when it finds a den, if it finds a possible girlfriend, his reaction to her is very evident. This is when the courtship begins.

The male begins to emit very particular vibrations, and then thumps its legs, in what could be a very specific and unique pattern for each species.

In most species, the female will immediately respond to his thumping with very similar thumping of her own. The male will then answer back, and these actions will be repeated about 4 times, at most, because the female will slowly be coming out of her den, and her epigynium will be engorged. Sometimes, the male will go into the burrow, and very carefully lure the female out in the open.

Haplopelma lividum copulating

We have to remember that the male’s purpose is to copulate, and the female is yet undecided.

This is when the tibia hooks come in handy. When the female is almost completely outside in the open, they begin tapping, and the male very carefully hooks the female’s chelicerae with his tibia hooks, leaving her unable to change her mind. Once he has pinned the female’s chelicerae, the male begins to perform a series of so called boxing movements, where using his pedipalps, he begins “boxing” on the underside of the female’s prosoma, continuing to emit his hypnotizing vibrations now and then.

Hooking and boxing


When the male senses that the female is completely ready, he proceeds to stretch his pedipalps reaching the epigynium opening and hooking her with his tibia hooks, and introducing his sperm into the spermatheca. This is very evident, since the male uses his hook to pull the epigynium towards him, practically bending her in half, and inoculating the semen.

It is likely that the process will be repeated with the other pedipalp, and if things are going well, he will probably repeat it several times. Once the male has finished, he pulls out his pedipalps from under the female, and starts to retreat, pulling himself away without letting go of the female’s fangs. As soon as he feels he is safe to leave, he disengages and runs away! We should not forget that he could easily become just another source of protein for the future babies. In my experience, I have noticed that the more females a male fertilizes, the more experienced he gets, and in many occasions he doesn’t even bother to go through the entire ritual. Sometimes I even think he is committing rape!

In captivity, we should consider the container to be the female’s burrow, so we should bring the male close to the container, and let nature take its course. However, we should always remain vigilant, and armed with a long object, to separate an unreceptive female if she tries to feed on our male. And if the copulation process is not successful, we have to be ready to help the male get away, being careful not to drop or hurt him, since they usually try to leave in a hurry.

This has been an interesting approach on the mating ritual. Now we will proceed to analyze the care that follows in captivity.

I always recommend placing the male with only one female a day. I have had bad experiences when doing this twice or more in one day. On the female’s side, I recommend two encounters with males to ensure sperm introduction. If we see the slightest attempt of the male to run away when it senses the female, we should always remove him immediately. Many factors can be getting in the way, and forced copulation will not result well. In average, a male has to copulate five times in order to begin the sperm web production process again.

Patience is the key work for this process.

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Reaching sexual maturity for females takes longer than for males. This happens around the age of 8 to 10 years of age. Therefore, we must be very careful if the female is not receptive to the male. It is very possible that she hasn’t reached sexual maturity and sees Romeo only as food!

You can tell females apart by their noticeably larger opisthosoma, and a more passive and tranquil nature than males. However, not in all cases are the females larger than the males. Due to their diets, sometimes males are larger than females of their own species, having the advantage of strength.

Egg sacks

In Mexico, tarantulas usually make their egg sacks around the months of March and April, so babies will hatch during the rainy season, ensuring they have abundant food available when they become independent. Once the female decides it is time to make her egg sack, she will start by setting up an immaculate white bed, patiently and slowly weaving it with her spinnerets.

Brachypelma auratum with recently laid eggs, weaving the top layer of web

Egg sack of a Brachypelma auratum

They spin such a large amount of web, that the ground is completely invisible due to the thickness of these layers. Once it has finished this step, the tarantula will proceed to position itself with the epigynium at the exact center of this cushion, and lay its eggs through the sperm sack and the epigastric furrow where they are automatically fertilized, since, as we remember, the semen had already been deposited in this sack. Depending on the species, the female can lay between 20 and 1,500 eggs. This can account for the variation in the time it takes each species to lay its eggs. As she is laying the eggs, they look like a beautiful pasta pellet soup. As soon as she is done, the female will begin to wrap them very gently with a web produced by her spinnerets, until they are no longer visible. We can think that now the egg sack has a shape of a little inflated tortilla. The tarantula will begin to pull on the edges previously fixed to the walls of her burrow, and bring them together to make a ball called egg sack. This makes it completely transportable. In some African tarantula species, females will leave the egg sack attached, and care for it there. In tarantula species that have urticating hairs, they will try to make a final layer with these hairs as a protection against some of their enemies.


Brachypelma smithi laying its eggs

Brachypelma smithi eggs

During the time she cares for her babies, she will rotate and massage the egg sack. We think she does this so the eggs on the bottom will not be crushed. If she didn´t move the egg sack, the eggs on the bottom would get crushed, and the dead eggs could attract bacteria and mites that would spoil the entire egg sack. This is why rotating the egg sack and gently massaging it is so important.

Video of a Brachypelma smithi making an egg sack and depositing eggs.

Later on, during the months of June and July, the babies will begin to hatch. They will work their way through the endless layers of silk. Once the babies are out, they will finish absorbing the rest of the egg yolk, and will remain together for a while and live in the company of their mother. After this, they will choose to leave their burrow and begin their independent lives. Sometimes, you will be able to observe that the babies have left all in single-file by following the traces of web they have left behind. Then, they will all break ranks and begin living their own lives. In some species, there is a certain degree of gregarious behavior, where the mother andbabies can co-exist for a while longer inside their den. Rick West has told of some cases where he has found several generations of Theraphosa blondie sharing the same home. But this is not always the case. Sometimes there is a very high percentage of cannibalism. Even inside the egg sack, some species can eat each other. Some specialists say that this will yield larger and better developed babies, but in my own experience, I have seen that the babies that ate their kin might start out larger and better developed, but the rest later catch up, so there is no real advantage in this. Gregarious behavior is more common in tree-dwelling tarantulas than in their ground-dwelling counterparts.

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