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The psocid "book louse" (Liposcelis bostrychophila) is the most common of the three species of psocid that are classed as pests in this country. This is the one that is predominant in this country.
Psocids lay their eggs singularly or in small batches. The eggs are in relation to the adult about 1/3 of the size. The eggs have four nymphal stages (three for males), the nymphs are virtually colourless and difficult to see on lighter backgrounds. This results in large infestations due to the psocid not being seen until it is an adult. The gestation time varies according to temperature from 22 days at 30°C to 56 days at 20°C. All adults of the species are female thus the insect is parthenogenetic and due to this infestations can result from one single egg.
Psocids feed on a number of foodstuffs:
Usually the only sign of infestation is actually seeing the psocids themselves when they are adults on surfaces and in foodstuffs in buildings, along with seeing them in cracks and crevices. Again, once the adults are seen the infestation is usually large. They are mainly found in humid conditions but can survive in lower temperatures.
The need for control of psocids is very much a difficult issue as the louse can be imported into a dwelling or work place through a variety of ways eg. foodstuffs from a factory or shop which have entered into the areas concerned, or the louse coming from a source such as packaging materials or transport.
In domestic and small commercial properties infested foodstuffs should be disposed of and surfaces along with crevices cleaned with suitable products. Storage of food in humid conditions is likely to increase the risk of infestations and where possible cool ventilated conditions should be used for storage.
Psocids being found often lead to Environmental Health issues being raised and this can be both embarrassing and costly to the people involved, this alone is a reason for control.