They look like tiny termites and can swarm in their millions, sometimes forming a moving carpet in grain storage areas.
Would you be able to identify Liposcelis?
Common name: Booklouse or Psocid
Scientific name(s): Liposcelis spp.
Description: Tiny, wingless, light brown insects, with simple anatomy, resembling worker termites a millimeter or less in size.
Geographic distribution: Worldwide.
Habitat: An increasingly common indoor pest, where they can be a problem in books and stored belongings. Commercial they can be a problem in food storage areas such as warehouses and grain silos.
They seem incapable of eating intact grain, but thrive on damaged grain, brewer’s yeast, skim milk, flour, nuts, and organic dust. The presence of fungi can also encourage them – moist, damaged grain is ideal. The also feed on the starch and associated moulds, in the paper and glues used in books and documents.
Most populations are entirely female. Indeed male Liposcelis bostrychophila, one of the most common species in Australia, were only discovered in 2002. Since the females reproduce by parthenogenesis, laying large eggs without needing to mate, populations can explode in number, until they form a living carpet of tiny insects.
Pest status: Can become a serious pest wherever grain-based foodstuffs are poorly stored. Humidity is a major contributing factor. Booklice taint grain if present in large numbers, and can provoke allergic reactions in the sensitive.
Booklice are also known to carry a number of fungi and bacteria, including the bacterium Rickettsia felis, which can be fatal to humans when spread by fleas. However, booklice have not been linked in the transmission of disease and there is no way for the booklice to directly infect humans since they cannot bite and pierce human skin. Oddly, Rickettsia is only found in the female-only populations, where it may be controlling their reproductive strategy.
Treatment: Sanitation of infested areas is vital – destroying contaminated food, and removing all traces of spilled flour, grain, or yeast, and reducing humidity levels (consistently below 50-60%). Booklice are also vulnerable to temperatures above 45oC.
In commercial situations, using pesticides is difficult, as resistance to pyrethrins, organophosphates, and phosphine is increasingly common. Storing foodstuffs in a controlled atmosphere, not only with reduced humidity but replacing oxygen with carbon dioxide can provide effective. Alternating controlled atmosphere techniques with pesticide treatments tends to be more effective than using controlled atmosphere techniques or pesticides alone.
Daniel Heald, technician and entomologist.