Dale Fort Blog Number 8

28 05 2012

Another article about another of the little-sung creatures you share your home with


The scientific name is Liposcelis corrodens.

Lipos = Greek for fat

Celis = koilia = Greek for belly

Corrodentia = Latin: To gnaw to pieces

The fat-bellied book-chewer

They belong to a group of insects known as “Psocids” pronounced ‘So-sids’

They are to be found in the cleanest of houses and are benign relatives of the parasitic lice that feed on blood or skin.  They are not dangerous to humans (but you probably wouldn’t want to eat them, see below).

   Lipocelis corrodens is non-sexual, there are no male insects.  Females lay unfertilized eggs that develop into genetically identical females (parthenogenesis).  In appropriate conditions a booklouse can lay 4 eggs a day.  This might not appear to be many but from the mother’s point of view an epidural might seem appropriate because the eggs are about a third as big as the adult.  Virtually transparent, baby Psocids hatch out after 1-2 months. The adult is pale, inconspicuous and about a millimetre long.  Black or very dark brown individuals (most often found on walls behind picture frames in my house) are probably a related species Lipocelis bostrychophila.  This latter species is thought to be commonest in the UK.

They are to be found everywhere in the world.  An absence of wings, coupled with the fact that on a bad day they could be outrun by lichens might lead us to question how they have managed this.  The answer is probably that they are dispersed by air currents.  A study in 1945 found them persisting as low-level aerial plankton.

Most books are made from wood which is not an easy thing to subsist on.  Wood- eating animals like termites can only digest it with the aid of the complex community of micro-organisms that dwell in their guts (baby termites inoculate themselves with these organisms by licking their mother’s bottoms and starve if they don’t).  Booklice can’t eat books directly but chomp instead upon the moulds and fungi that can.  Two stiff rods support the head while the biting jaws chew up the food.  It could be argued that booklice are a force for book-conservation because they remove paper and gum digesting fungi.  In the long run, it’s probably better to get rid of both.  An easy way to do this is to heat and desiccate them (a hair dryer will do the job).  You should think carefully before applying this treatment to your First Folio Edition Shakespeare.

The other place you might find these animals is in stored foods, especially flour.  They feed on the flour and favour the dark warm crevices found in paper packages in kitchen cupboards.

In 1996 Bryan Turner of King’s College purchased packets of flour in pairs from a variety of supermarkets.  One of each pair was put in a kitchen cupboard and the other was sealed in a plastic bag.  After a week the kitchen packet was also sealed in a plastic bag.  All the samples were then kept at room temperature for three months.  Upon examination, 17% of the kitchen packets (22 out of 133) were infested.  None of the control packets (those sealed immediately) were.

Some years ago I discovered an infestation in one of our cupboards.  I threw away the contents and disinfected the cupboard.  An electric fan-heater was then directed into the interior to make it hot and dry.  To this day, the Psocids have kept away.  We moved the flour to a higher, drier, lighter place and it seems to work.  Another useful tip is to actually use the food items you store.  If something’s 7 years after its “best by” date it’s almost certainly being eaten by something other than you.


Dale Fort Blog Number 7

10 05 2012

The blog reverts from historical history to natural history and tells you much you might wish to know about  those unsung heroes of the three-tailed world:


 A silverfish

Between 1985 and 1988 when I was privileged to live at Dale Fort, I developed a sleeping arrangement then revolutionary on The Dale Peninsula.  I spent each night on the floor, on a thin roll-upable mattress that I could pack away into a cupboard every morning.  Pioneering the futon meant I could maximise the floor area of my very small room during the few conscious moments I spent there when not teaching.  A secondary benefit was that I developed a close acquaintance with the thousands of silverfish who shared the accommodation.


Silverfish are members of a group of insects known as bristletails.  Moderately close inspection will reveal their three tails, the middle one being the longest.  They are not very large (maximum 15mm or so) and mostly harmless.  The reason I got to know so many of them by sleeping on the floor was because they tend to be inactive during the day, dwelling in crevices like the gaps between floorboards.  They emerge at night and run about very fast in search of food.

Their food comprises a wide variety of stuff.  In non-domestic situations they are found in woodlands, grasslands and on seashores feeding on algae, fungi, lichens and higher plants. (The seashore bristletail is called Petrobius.  It’s found on the upper shore and if you sneak up on it you can literally make it jump because it flexes its abdomen like a spring and bounces away).  They eat mostly dead material and help convert complex compounds into simpler substances that plants can absorb.  In jargon they would be called detritivores because they eat dead stuff (detritus).  Being fond of dead material they will chew on things like natural fabrics, paper, glues and wall-paper paste and so they may do some damage to fixtures and fittings.  They will also feast on the corpses of their friends and relatives (or indeed their enemies) given the chance.  This seems a little gruesome from our point of view but humans do it too in extremis and ultimately we are all detritus.

Bristletails are thought of as simpler than most insects but the males still indulge in ritual behaviour when it comes to reproduction (mind you, so do sea anemones and they’re simpler than any insect).  Fertilization is external but chaps do grab hold of girls to help ensure that sperm and eggs meet.  The males deposit a packet of sperm (spermatophore) on the ground and the female uses it to fertilize her eggs.  20 or so eggs are deposited in crevices and hatch any time up to several months later.  The female cannot store sperm and has to find a new packet every time she lays eggs.  The babies are miniature versions of the adults and moult about 8 times, sometimes over several years to become adults themselves.

Palaeontologists reckon that bristletails have been around for a very long time.  It’s believed that they have not changed much in the last 300 million years and can be thought of as an insect equivalent of the coelacanth but much older.  When the first fish-like vertebrates where crawling from the sea, they would have crept onto land already occupied by bristletails.  They are known to have been especially annoying to dinosaurs with ticklish toes and they’ll probably be around long after we’ve all disappeared.