Is my spider a boy or a girl?

At some times in a spider’s life it is easy to tell whether it is a male or a female, but at other times it can be impossible. This is because the reproductive organs of a spider do not develop until the spider has reached maturity. Juvenile male and female spiders look almost exactly the same. As a spider grows, it sheds its skin, or moults, several times. The reproductive organs do not develop and become visible until after the final moult.

The most reliable character to use to distinguish male and female spiders is the position of the reproductive openings.

Female spiders

The female reproductive opening is located on the underside of the abdomen, near the front of the spider.  It is called an epigynum and is often hardened and dark in colour.

Photo of a female Badge Huntsman Spider underside

Female Badge Huntsman Spider underside. Note the reproductive opening, the epigynum (arrowed).
Photographer Alan Henderson / Source: Museum Victoria

Male spiders

The male reproductive system is a bit more complex. The testes are located on the underneath of the abdomen, and connect to the surface via a small tube. The male spins a small mat of silk and deposits a ‘packet’ of sperm from the testes onto the silk mat. He then syphons up this sperm packet into a reservoir, called an embolus, located in the last segment of his palps. This is why the palps of a mature male spider resemble tiny boxing gloves.

Photo of a mature male Jumping Spider

A mature male Jumping Spider (Salticidae). Note the ‘boxing gloves’ or swollen last palpal segments (arrowed).
Photographer: Ken Walker / Source: Museum Victoria

Reproduction

To fertilise the female spider, the male spider places his embolus into her epigynum, transferring the sperm packet, where it is stored in a pocket to be used by the female at a later date.

Further Reading

Brunnet, B. 1994. The Silken Web – A Natural History of Australian Spiders. Reed Books: Melbourne.

Lindsey, T. 1998. Spiders of Australia. New Holland Publishers: Sydney.

Walker, K. L., Yen, A. L. and Milledge, G. A. 2003. Spiders and Scorpions commonly found in Victoria. Royal Society of Victoria: Melbourne.

Comments (13)

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Norman Tulloch 1 May, 2010 03:07
The article on this page says, "Unlike insects and other organisms, male spiders do have a penis." Shouldn't there be a "not" in that sentence, so that it would read, "Unlike insects and other organisms, male spiders do NOT have a penis"?
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Discovery Centre 18 May, 2010 16:30

Hi Norman, thanks for your comment. We agree and think the text should maybe read something like male spiders have a penis-like structure. We will try to get this updated as soon as possible.

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zymoine(simone) 2 June, 2010 22:49
this was very helpful and i got my answear, thank you.
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justine 6 April, 2011 21:53
what a big spider is that hehehehe!!! is that a gilr or a boy???
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maddy 7 September, 2012 01:49
ta tht helped me wiv my spider :)
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Kat and Erin 19 February, 2013 08:10
We think this is helpful but who the heck would be brave enough to take a look there and hold it?!?! I mean be real....
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james ionn 10 March, 2013 06:02
hi, i have a chili rose how do i know if it is male or felmae it has just shed, i really cant find any hole on the abdomen or any sperm glands on the front help?!?!?!?!
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JACK 16 March, 2013 05:03
SCAREY!
Kimberly motley 11 October, 2013 07:12
i just caught one of those :)
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zeppelin 28 June, 2014 17:56
do huntsman spiders eat pinhead crickets and how do u know if its a boy or girl please comment
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Discovery Centre 30 June, 2014 14:10
Hi Zeppelin, huntsman spiders will take crickets. Regarding how to tell whether your spider is a boy or a girl it can be quite difficult as is explained higher up in this sheet. While the spiders are juveniles it is nearly impossible; but once they are adults have a look at the palps of the spider. For males the palps should be enlarged or modified, see the information given above. Have a look online at images of male and female adult huntsman spiders so you can get an idea of how the palps vary between the two sexes. 
Jenny Paterson 17 October, 2014 15:13
I have a photo of a big slow old huntsman I was going to send you but the email address seems not to be working. Cheers Jenny
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Discovery Centre 18 October, 2014 13:50
Hi Jenny, we're receiving email to discoverycentre@museum.vic.gov.au just fine - perhaps try again?

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