Thirsty work for spiders

SOMETIMES the most interesting aspects of nature can be found by looking closely at small things.

I got an email the other day from a reader who has obviously discovered this fact. He started by explaining... “On my way up to school with the kids there is a small bridge that we stop to look at each morning. There is always something interesting to be discovered.”

He went on to explain the kids’ delight at finding something as small and mundane as a baby snail.

Then he described a spider on the bridge parapet. The kids followed the spider with their fingers.

“The morning had been very cold and when we lifted our fingers there was a thin film of moisture on them. The spider had its mouth-parts lowered and appeared to be harvesting the water. The question I have is that I had assumed that they got all their liquid requirements from the body fluids of their prey and that they didn’t need to drink, rather like rabbits, which get most of their water from the grass that they eat. So do spiders drink water?”

As is quite often the case, a question had arrived in my inbox the answer to which I didn’t know. Spiders not being insects, they are a rather specialised area of study and it can be hard to get information about them. But, thanks to the internet, I found the answer.

There are a few spider species, including the notorious black widow, that do, as the reader suggested, get all their liquid requirements from the body fluids of their prey. But the vast majority of spiders, including all Irish species as far as I can gather, drink water and some species will go to extraordinary lengths to get it.

There are species that live in deserts that construct large and elaborate water traps out of web in order to capture night time dew. Spider web is good for trapping moisture, which is obvious along any Irish hedgerow early in the morning. Many Irish web-spinning species, including the common garden spider, eat their webs every morning and get their daily water intake from the droplets of dew.

Wolf spiders, which don’t spin webs, will spend time scavenging for water droplets from any available source. This is one of the reasons spiders are particularly common in kitchens and bathrooms.

And all spiders kept in captivity, including tarantulas, must be provided with a source of drinking water. A piece of moist sponge is recommended for the smaller species and something like a bottle cap filled with water for the larger ones.