Sexual distribution of eggsacs

Wonder Walrus

Oct 9, 2008
I've been on the boards a while, and I've additionally searched this topic to no avail, so I figure it may be beneficial to start a thread regarding this discussion.

Has anyone ever done a study into the ratio of males vs females within single broods of offspring? Or in basic terms, is there a pattern in the amount of males vs. females spawned from a single eggsac?

I'd imagine, given the males shorter lifespan, that more would need to be produced with each clutch to ensure there are sexually mature males present as often as possible, but this is based in no research or study what so ever.

Has anyone experienced with breeding ever noticed a lot more males than females? Is it a 50/50 distribution? Does it depend on the species?


May 15, 2008
I have handled a few egg sacs and i haven't seen a ratio other problems is most people who breed do not hold onto the entire sac, for to long. It would be interesting to see if someone did.


Old Timer
Nov 5, 2007
I would assume this would be hard to determine for the casual enthusiast considering that each sac depending on species produces hundreds (if not thousands of eggs). Then on top of that the keeper would have to raise the slings to a size where the spiderlings were of a size that was easily distinguishable between male and female.

In my opinion, most hobbyists don't have the time/space or patience to be able to do this. Especially with the slower growing species. For example, I have some Brachypelma slings that are over three years old and the largest one is barely 1.5" in legspan.

Too many variables:
Does the ratio of M/F vary based on Natural Habitat vs Captive Bred?
How many sacs would have to be studied to get a good idea? Each sac could vary in ratio of M/F.
How many eggs were produced vs the individuals that actually made it to a sexable size? Did more males vs females die?
Does time of year that the tarantulas are bred/produce a sac affect the ratio?
Does the ratio vary between genus or species of tarantula? OW vs NW? Slow growing vs fast growing?

I agree that these would all be very interesting things to study but in my opinion the studies would have to be more specified and be done in a highly controlled environment over a period of years to even get a good thesis. Perhaps if I pursue a graduate degree in entomology this would be an interesting subject to do my studies in. {D

DISCLAIMER: The above information is a matter of opinion and not meant to be taken as "fact". ^_^