Each autumn the number of spiders seen indoors suddenly increases as males go on the hunt for a mate. The Society of Biology has launched a new recording scheme and is asking everyone who sees house spiders to report their sightings. The free app 'Spider in da House' is available in the Android and Apple app stores.
Dr Rebecca Nesbit from the Society of Biology says: "We are recording the large, hairy Tegenaria spiders, which are most often called 'house spiders'. The number seen in houses increases in the autumn, and we want to know the timing. Is it the same time everywhere in the UK? Is it the same time each year? Is it related to weather conditions?"
Tegenaria spiders normally live in sheds, garages and wood piles, where they produce a sheet web with a funnel-like retreat at the rear. Both sexes remain in their webs until the autumn when the males become nomadic and search for females. This often leads them indoors where we encounter them in our baths or running from beneath our sofas.
By recording sightings of house spiders, it is possible to investigate the timing of this year's mating.
Professor Adam Hart from the University of Gloucestershire says: "By eating flies and other insects, spiders are not only providing us with a pest control service, but are important in ecosystems. They often feed on the most common species, preventing a few species from becoming dominant.
"We're interested in sightings from around the UK, and we're looking forward to seeing all the photos coming in from those people brave enough to take them!"
Many species of spider can take a wrong turn and end up in homes by mistake. These generally die unless they find their way back out as it is too warm and dry in our homes and there is no food available to them. A small number of spiders, however, have adapted to living indoors. The Spider in da House app also has photos and information to help identify the spiders we share our homes with."
Tegenaria is actually a group of closely related species, five of which are found in houses, but it is usually impossible to tell them apart without a microscope.
Unlike in most mammals, female spiders are often larger than males. In Tegenaria spiders, males are readily distinguished from females because males have what look like a pair of long thin 'boxing gloves' protruding from the front of their head end. These pedipalps, often just called palps, are used to transfer sperm into the female.
Females usually stay in their webs, which are often found under the shed, and await a suitor. After a male has found a female's web he will stay with her for a number of weeks, mating with her repeatedly.
The female then overwinters with stored sperm, and the next spring she can produce more than 10 egg sacs, each containing around 40 to 60 eggs.
Dr Rebecca Nesbit from the Society of Biology says: "We are trying to collect as much data as possible from around the UK. It is amazing how much there is still to discover about even the animals that live closest to us, but scientists can't collect this much information alone. We can only perform this study with the help of interested people around the UK – thank you very much!"
For more information please visit www.societyofbiology.org/housespiders. Records can also be submitted online, and experiences can shared on twitter using #SpiderindaHouse and #SpiderSeason.
The house spider survey follows the success of the flying ant survey, for which thousands of records have revealed a more complex pattern of flying ant emergences than expected. It is a collaboration between the Society of Biology and the University of Gloucestershire.
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