I have been hearing this question more and more lately so I thought I would give some helpful tips about how to know if your jumping spider is a male or a female. First, I want to address a rumor.
Chelicerae coloring does not determine gender
For those that don’t know what chelicerae are, they are essentially the jaws of the jumping spiders. They hold the fangs, and they help hold or move their prey while the spider eats. Like your jaws, they are very useful, but not for determining gender.
I also want to mention that the information below is in general terms. Inevitably I will get a guru who will tell me, “Ok, but the males of this species also have this trait.” And of course, I am not a scientist, I don’t know if that is true or false, and have likely never heard of that species before, and there are so many variables that there is not a possible way for me to address them all without becoming a scientist, and even then, there are species out there that they have never heard of, so…
Ok, enough of all that.
Males:
Generally speaking, males will have a more narrow abdomen. You can see this picture of an adult male and female audax below for comparison.
An adult male will also have bulging pedipalps.
Yes, the pedipalps look almost like boxing gloves, and there is a very valid reason for that. I have written about the use of a males palps before, but it seems appropriate to discuss their purpose here too. A male’s pedipalps are an important part of a jumping spider’s reproductive system.
Yes, you heard that right.
When a male is on the hunt for a mate, he spins some web, drops some sperm from his abdomen onto the web, then draws the sperm up through an opening in his pedipalps. He stores the sperm in his pedipalps in something called the sperm duct. When he has found the love of his life and wins her over without becoming dinner, he uses his palps to deposit the sperm.
True story.
And that is why a male’s palps are so much bigger than a female’s.
Females:
Again, this is just a generalization for most species of jumping spider I am familiar with. Generally speaking, a female will have a much bigger abdomen. The main reason for this is obvious; she needs to store the eggs somewhere. A female does have pedipalps, but they are much smaller and are not used for reproductive purposes.
Females also have an epigynum. This can be seen on the underside of their abdomen and looks like a little slit. This is how her eggs get fertilized, and how she lays her eggs.
That’s it, those are the main common differences between males and females. Sometimes a female will have a narrow abdomen, or a male will be a big eater, so he will have a bigger abdomen. It can get confusing, especially when they are juveniles. I totally get the confusion, I have been tricked before and will probably be tricked again. Depending on the species, juveniles can be confusing. The best advice I can give is to wait until they are an adult.
While those are the main differences between males and females, there are some species that have drastic physical differences. For example, in the orange phased regal jumping spider, the males will be black 100% of the time and the females will be the ones with orange in them.
Also, some species like the M. mormon have a very different face.
These physical traits make it so much easier to tell the difference, but not every species has these drastic physical differences, so keep an eye on the palps and abdomen.
I hope this helps! Let us know in the comments if you have another helpful way to determine a jumping spider’s gender.
