Photos by Reyer Boxem / Video by Lidian Boelens

On safari in Huize De Voorraadkast

Mice in your kitchen and mites in your bed

A dirty house must be home to a lot of interesting creepy crawlies. Biologist Martine Maan went looking for the resident fauna in Huize De Voorraadkast, probably one of the dirtiest student houses in the city.
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Door Emily Zaal

8 October om 10:38 uur.
Laatst gewijzigd op 22 November 2020
om 16:16 uur.
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By Emily Zaal

October 8 at 10:38 AM.
Last modified on November 22, 2020
at 16:16 PM.
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Emily Zaal

Student-redacteur Volledig bio Student editor Full bio

Classical music by Chopin resounds through the hallways of Huize De Voorraadkast. Near the door, bags of garbage look ready to explode. Half empty beer bottles are scattered around the hallway and dried-up teabags are stuck to the ceiling. But the fourteen housemates (fifteen if you count their cat) in this student house don’t mind the mess at all.

Many students think it’s perfectly normal to live in a house where no one ever cleans up. Messy houses are often associated with insects, mice, and other vermin. Does every dirty house have creatures running around? Biologist Martine Maan investigates. 

Daddy long-legs

When the door opens and Maan sees the garbage in the hallway, she is taken aback, which makes econometrics student Lisa van der Leij and built environment student Jurjen Randag laugh. 

Spiders are really useful because they eat bugs

But then Maan spots the first critter of this mini safari, up in the corner near the ceiling. ‘Look, it’s a daddy long-legs spider’, she says, pointing upwards. ‘There, on the other side, is a little nest of eggs. But that belongs to a different species.’

‘Ew’, Lisa and Jurjen say simultaneously, sharing an uneasy smile. Knowing that there are bugs living in your house is apparently not as bad as actually seeing them.


‘Spiders are really useful, of course, since they eat bugs’, says Maan. ‘You need an ecosystem in your house.’

Daddy long-legs spiders usually carry their eggs in little sacs in their jaws; it looks like a little grey ball.  The higher up you go, the fewer creatures you’ll find. If you’re looking for spiders, check the ground floor.

Photo by Reyer Boxem

The socially distanced safari continues up the stairs, where the second specimen in this biotope presents itself: house cat Rubert-Jan. While Rubert-Jan rubs up against Maan’s leg, she enthusiastically talks about her own student house. ‘One time, I got back from vacation when it was really hot’, she says. ‘The garbage had practically liquefied and there were maggots everywhere.’ It was the first and the last time she ever used chlorine to clean. ‘You shouldn’t use that really; it kills all the good fungus and bacteria, too.’

Fruit flies

The safari continues to the roof terrace, where tattered flags blow in the wind and a few folding chairs have been dumped in a shallow pool of water. ‘What kind of bugs and creatures do you see around here?’ Maan asks, looking around. ‘Since we got Rubert-Jan, we hardly have any mice’, says Lisa. ‘Before that, we had an infestation.’

‘We also have a lot of silverfish’, adds Jurjen. ‘And fruit flies, obviously, and we occasionally get maggots, when we leave the garbage out for too long.’

Since Rubert-Jan, we hardly have any mice

A small group of flies circles the beer bottles left out on the roof. Maan squishes one between her hands. ‘Not the most scientific way to study them, I know’, she says sheepishly.

But these flies aren’t fruit flies; those fly much slower. ‘I did see some inside. A lot of people mistakenly think fruit flies are attracted to fruit. But it’s the fungus on the fruit they like’, Maan says. ‘They lay their eggs in it and their young grow up in the fungus.’ 

Dust mites

Rubert-Jan meows, calling everyone back in. Maan says the carpeting in the hallway also attracts bugs. ‘They love carpet, but you often can’t see the critters. In a student house like this I’d expect a lot of dust mites in the carpet and the beds. There will also be loads of bacteria and fungi’, says Maan, ‘but you’d need a microscope to see those.’ 

Photo by Reyer Boxem

Next up is the toilet. Maan jumps back as the door opens. ‘Oh, I’m definitely not touching anything in there’, she says. ‘This house must be very good for your immune systems.’ The toilet is where you’d expect to see silverfish, although they make themselves scarce when you turn on the light. 

Go live out in the woods and you’ll see how many critters there are

Another couple of housemates arrive, jumping over a pile of paper waste to enter their rooms. ‘I’m surprised at how little we actually found’, says Lisa.


Maan nods, a little disappointed it seems. ‘I would have expected more in a student house like this.’ But Huize De Voorraadkast is located in a busy street in the city centre, which means there are fewer critters anyway. ‘They’re inevitable’, says Maan. ‘Go live out in the woods and you’ll see how many critters there are.’

‘Does that mean our house is clean enough?’ Lisa asks, sounding relieved. 

Maan laughs. ‘That depends on your perspective. I certainly wouldn’t want to live here.’ 

The ecosystem in your student house

‘At home, you’re never alone’, says Matty Berg, professor of soil fauna and natural ecosystems dynamics. He speaks from both professional and personal experience; he used to live in a student house ‘where cleaning was not a priority’.

He even remembers when they had a cockroach infestation. ‘Except we never saw them during the day, since they’re nocturnal. We’d go out to the pub, come home late, and turn on the light to see hundreds of cockroaches everywhere! There was also an ant colony. Tens of thousands of ants in our house. They do no harm, of course, but I can imagine that people don’t like it.’

Nocturnal animals

Berg has turned his fascination with creepy crawlies into his profession. He even discovered fifty-two new species in the Netherlands, and one that was new to the rest of the world. 

He is an expert on all the insects and animals that student houses attract: mice, silverfish, dust mites, spiders, fruit flies, and more. ‘Many insects and other bugs are nocturnal’, Berg says. ‘During the day, they hide in all the dark corners, nooks, and crannies.’ But they come out at night. 

Just annoying

This also includes critters you can’t see with the naked eye. ‘Dust mites that are only two millimetres long like to sit in the corners where dust accumulates’, says Berg. All these little creatures serve a function, though: they eat all the harmful crumbs, fungi, and bacteria. ‘Very few of these creatures actually have any effect on our health’, says Berg. They’re really more annoying rather than harmful. Silverfish can damage paper and eat books.

‘An inside environment is basically an ecosystem in and of itself’, says Berg. ‘All these critters are connected to each other in “who eats who” relationships.’ Spiders eat mosquitoes and flies, saving you from being annoyed by them. How big the inside ecosystem is depends on a few things. ‘The kinds of creatures you see inside depends on the environment, like whether it’s dry and warm or cold and damp, and on the food there is for them to eat. But it also depends on how easily they can enter the house, and whether the house is located in an urban environment or near a park, for instance.’



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