Spiderman or Spiderwoman?

Philippa Skett, intern at the Society of Biology, is working on the house spider survey

With the seemingly terrifying invasion of common house spiders (genus: Tegenaria), illustrated by the many spider photos we’ve received, it is easy to forget just why they are cowering in corners, scuttling along skirting boards or skulking down the sides of our beds. Their expedition into our homes is part of their life cycle, and there is no fairer sex when it comes to Tegenaria – both genders have to be vicious to be victorious.

Male Tegenaria spider, one of the many photos sent in to our House Spider Survey. Credit: David Reeves

It is often the case that a spider found within the house this autumn will be a male, as the females tend to remain within their webs, sometimes under a shed or in the attic. Males restlessly wander in search of waiting females, and this is why around this time of year they are seemingly more visible than ever in our houses.

Males come with the added bonus of looking more terrifying than usual – upon sexual maturity, the tarsi of the males front pedipalps enlarge as they develop into a palpal organ, making a spider look like he is armed with boxing gloves (as in the photo below).

The Palpal organs are used to transfer sperm into the abdomen of the female during mating. This difference is easy to notice if you find a spider in your house this autumn. Females have smaller palps without the ‘boxing gloves’.

A close up of the head of a male spider, with their pedipalps hanging down in front of their legs. Source: www.radleyvillage.org.uk

Should the male survive being whacked at with a newspaper and come to find a female, they still need to then approach her carefully. Females will trail threads of silk within their webs that contain pheromones to deter competing spiders, and this will only alter when ready to mate. Not only that, should a male find a potential mate one moult away from maturity, he may guard her to ensure no other male can access the female he has had to laboriously track down.

In some species of Tagenaria, even if a female does let him mate with her she will sometimes proceed to eat him afterwards. In this way, the male can contribute to the health of the offspring indirectly by providing nutrition for their mother. She has a gruelling winter ahead of her as flying insects decrease in number, so food becomes scarce.

A female Tegenaria forming her egg sac

 When the weather warms, the female then weaves multiple egg sacs to hold around 50 precious eggs, which she laboriously decorates with insects. Usually the female dies shortly after producing her egg sacs, but some may outlive the winter and reproduce once more.

So, who has the harder life, spiderman or spiderwoman? Males have to fight off competing males, possibly unreceptive females and even escape humans. Conversely, females have to simply sit and wait for a male to approach, although after that she is faced with the task of building her egg sacs and decorating them and some species even leave insects in their webs to feed the newly emerged offspring.

It seems that there is no easy way of life for Tageneria; males and females alike must sacrifice a great deal to bring a scuttle of spiderlings into the world.