In my experience bathrooms in older houses always seem to be cold, damp places. In my own bathroom this is probably because I hardly ever have the heating on, currently being young and mobile enough not to have to do so. I sometimes visit people who have underfloor heating and think how nice that would be, but not for long. For the bathroom is the last bastion for some interesting invertebrates.

Ancient Invertebrates

One year we went on holiday to the Isle of Wight, to look for Glanville Fritillary butterflies and other island exotics. Our accommodation for the week was in the clock tower of an old coach-house. 

We made one of the most exciting discoveries of the week on the first night when I went for a shower and found a very odd creature awaiting me in the shower tray, quite possibly the weirdest creature I’d ever seen (and I’ve seen a few!). 

I wasn’t exactly sure what it was, so popped it in a specimen pot and had a close look. It was about 2cm long, blackish-grey in colour with an iridescent pink sheen and a three pronged ‘tail’. It looked part seal, part lobster and much like an oversized silverfish. ‘Oversized silverfish’ wasn’t far from the mark as it was actually a bristletail, the first one I had ever encountered. As well as the three-pronged ‘tail’ it had long antennae and greatly enlarged palps. It was an altogether magnificent, prehistoric-looking creature. 

Bristletails belong to the order Archaeognantha which translates as ‘ancient jaw’. Their ancestors first appeared in the mid Devonian period, around 400 million years ago.

Primitive Life Forms

Another ‘primitive’ insect is the Silverfish, Lepisma saccharina. It is a rather quaint little creature and reminds me of the cybermats from very early ‘Dr Who’ episodes.

Silverfish seem to glide and roll along in a directionless manner like a drop of spilled quicksilver from an old-fashioned mercury thermometer. Their bodies appear to be covered in plate armour but they are actually quite soft and easily accidentally squashed if you try to pick one up – best to put a piece of paper in front of them and get them to go onto that so that you can get a closer look at them.

They like cool, damp places where they feed on starchy or sugary substances (hence the specific name saccharina) including plaster, paper and certain glues. They also eat dead skin cells and other such dust and debris so can be benevolent little cleaners, although their taste for book bindings can be problematic. But then if you value books you shouldn’t keep them where the humidity gets above the 75% required by Silverfish in the first place.

Silverfish originated around the same time as bristletails and they are have hardly unchanged for millions of years. They never develop wings and there is very little difference between juvenile an adult stages with no metamorphosis involved. They may be ‘primitive’ but they are perfectly adapted to their way of life and will probably be one of the few creatures still around when we humans have totally messed up the planet for a lot more evolved and sophisticated species.

I think of silverfish as something a bit old-fashioned, and part of my childhood. Whenever you turned a light on at night in the kitchen or bathroom there would be one that immediately darted off in a series of spiralling motions until it located the skirting and disappeared beneath.

I rarely see them these days in the age of centrally heated houses but I remember doing up the kitchen in our terraced house and finding several when I prised off some badly applied wall tiles. As well as plaster coming off there was a little clutch of silverfish spilling out. I had accidentally made an entire family homeless, but I am pleased to report that they relocated to the bathroom. 

The (False) Scorpion King

Pseudoscorpions are tiny arachnids only mere millimetres long. They have four pairs of legs like spiders but their pedipalps are modified into large pincer-like claws that make them resemble a scorpion albeit without the stinging tail.

They often freeze when disturbed but then will rapidly run away usually backwards. While some have eyes these are only sensitive to light, others are blind.

They navigate their way around and locate prey (and each other) by use of sensory hairs called trichobothria which are located on their pedipalps and also on their rear ends, helping them know what is behind them. They are sometimes found hitching a ride on another invertebrate by clinging on to a leg. This is known as phoretic behaviour, a great way for such a tiny creature to disperse to a new habitat.

There are 27 species of pseudoscorpions in Britain and they are found in a variety of habitats, often in leaf litter, under stones or even in bird’s nests. A couple of species are synanthropic (associated with humans) and can be found in buildings.

I have only ever found two pseudoscorpions, and they were both in bathrooms. I do not know what species the first one I found was as I had no way of identifying it. It was under a loose lino tile at the back of the toilet where it was perpetually damp from condensation dripping off the cistern. Insulating the bathroom and putting down cork floor tiles solved the damp problem but unfortunately put paid to the pseudoscorpions for I never saw another one in that house.

My second pseudoscorpion was in my current house, again in the bathroom. At first I thought it was a cat flea but as it didn’t jump when I put out a finger I figured I had something interesting, and so it was, a beautiful little Chthonius ischnoceles. This is the second commonest species in the UK. They are usually found in leaf litter so I’m not sure what it was doing in my bathroom. It could well have come through the airbrick it was next to or may have been living under/behind the skirting board.

In the Midnight Hour

It is also in the bathroom where I have only ever encountered the lovely little Goblin Spider Oonops domesticus, an arachnid blessed with a great English name as well as a nice scientific one. It is pretty small and is unusual in a British spider in that it only has six eyes (most UK species have eight). They are well-known (amongst arachnophiles that is) for being out and about in the small hours, after midnight, during ‘the witching hour’, which is possibly why they are called goblins. Michael Roberts recalls seeing the first one in his house around 4.00 am when he was working on the colour plates for his magnificent work on British spiders. One crawled over the plate he was working on, that of Oonops itself!

They are very pretty little spiders, a pale pinkish or apricot colour with the six eyes set close together in a tight group. They move very deliberately, with a stop-start motion, rushing forwards only to revert back to their slow progression. They are nocturnal wanderers, found indoors on walls or ceilings as they search for prey.

For background information on insects, I recommend the Royal Entomological Society website. The Classification of insects pages are a good place to start.