Spiders · Urban Ecology · Biodiversity

Is this spider male or female?

I promised a while ago to explain how to tell the difference between male and female spiders. It’s one of the most common questions I get asked, especially by kids when I point out a mummy or daddy spider!

On a side note, I met so many kids during my garden surveys that were fascinated by the spiders we were finding, and asking really great questions too! It really made my day. If these kids keep on asking questions like this about everything they see around them they’re going to make great scientists one day.Anyway back to sexing spiders…hmmm…Firstly, as you might know, most females spiders are larger than the males. This is called sexual dimorphism and it is a result of smaller males having an evolutionary advantage (ie. they are able to sneak in and mate with the female, or avoid being eaten by her afterwards!).Here is a photo I took of a very large female of my study species Nephila plumipes. Can you see the tiny little male on the left?

But sometimes the males of this species are also quite large (comparatively). The photo below is a male (right) with an immature female. This large variation in the sizes of males can happen (in an evolutionary sense) when males have an advantage if they are EITHER large (ie. more likely to out compete a smaller male) or very small.

In some species the males are always the same size, or even larger than the females. This photo shows a pair or Garden orb weavers (Family Araneidae, Genus: Eriophora)

The one on the left is the female and the right is the male. The way I can tell is by looking at the palps, the appendages near the mouthparts. The male has large palps with bulbous ends, he uses these to deposit sperm into the female. In comparison the female has long thin palps.

Females also have a genital opening called the epigynum near the book lungs on the underside of the abdomen (although this is harder to see). In some Araneidae species there is an interesting protrusion from the epigynum, I’m not sure what this is for. This photo comes from the Cross spiders I was studying in Germany, more on that later.

2 Comments

  1. Gabi's Gravatar Gabi
    December 1, 2017    

    Hi.

    I have “adopted” a spider in my room because I’m trying to combat my arachnaphobia. I called him Dougie, although I don’t know if it’s a male or female.

    I was hoping you could help. I think it’s a species of selenops but I don’t know. I’m not very educated in that department. Where I live, it’s a common house spider like the daddy long legs we have. So, we’re used to seeing them inside. It’s too hot for them to be outside. If you could tell me what kind it is I would appreciate it.

    I live in Namibia. The spider I’m talking about is dark brown with light brown stripes. It’s flat against the wall with its legs extended out. When they run, the lift and it looks like they are jump-sprinting. Weird. They are very skittish, but some are not, allowing you to come within close range. Not good when my mom is around. The abdomed looks almost diamond shaped, small head and large mandible. I don’t know to what size they can grow, but the largest I’ve seen so far was about the size of a plum in diameter… I think. I didn’t want to get close enough to find out. Dougie is about the size of a R5 South African rand, so still immature I reckon. He’s not skittish. He sits next to my bed… a lot. He even follows me. I don’t think they bite, I hope. So, is Dougie a kind of selenops? And how would I tell if Dougie is male or actually a Doris? And then… what do they eat? Because Dougie seems to be quite find of the small fruit flies in my room. Those tiny little annoying bugs that love spoiled fruit or sweet things. (I have an experiment going on the growth of fruit mold as a natural insecticide for orchids)

    Thank you kindly for a response. If no response, oh well. I tried. Have a great day though and a lovely holiday season.

  2. Megha's Gravatar Megha
    January 28, 2018    

    It was very helpful for me to identify the spiders . I really didn’t knew about it .

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