Order Psocoptera

Structure, Appearance and Characteristics

Psocids or Book Lice (also known as known as Paper Lice, can often be found crawling in large numbers over stored papers, books, walls, furniture, and other materials in damp, warm, undisturbed areas in buildings especially during the spring and summer months. They can be readily introduced into a new habitat on furniture, boxes, books and paper.

They feed on microscopic mould and mildew associated with high-humidity conditions. Outdoor species are also known as Barklice since they are found under tree bark or leaves.

They can be found on walls, in cupboards, in stored foodstuffs, in wall voids and behind electrical power outlets.

Psocids do not bite humans or animals, spread disease, or damage household furnishings. However, skin irritation may occur on sensitive individuals and some animals. Psocids are less than 1 mm – 10 mm in length, but Booklice are less than 5 mm in length. They most active during daylight hours. Females are wingless, whereas males have two clear membranous pair of wings. They have a large head, a flattened body with medium to long thread like antennae that is often at least half their body length and six, short stocky legs. They have chewing mouthparts and the mouthparts are held downwards when at rest.

Colouring ranges from almost colourless through grey to light brown, and the young are almost colourless.

Psocids are extremely agile and fast moving. They are poor fliers, and when disturbed will only fly off in short bursts. They are agile and fast moving, small and conceal themselves well making them difficult to detect in may cases.

Life Cycle

Booklice are almost all females and development occurs from unfertilised eggs (parthenogenesis). They have a gradual metamorphosis (egg – nymph – adult) and the egg incubation period is approximately 21 days, but can last ‘over-winter’ with newborn in early spring. The nymphal period 24-65 days, and the nymphs will moult 2-4 times. The female lays average of 20 eggs during winter and 50 eggs during summer. They are reasonably short lived with a total life span 24-110 days.

Habitat

They prefer damp, warm, undisturbed situations and often will be more noticeable during spring and summer. Manufactured material of plant origin that supports mould growth will encourage infestations.

Food

They feed on microscopic mould that grows on such things as paper, books, bindings, wallpaper glue, leather and straw. They show a liking for starch.

Pest Status

Booklice can become a nuisance due to their presence in large numbers, but they do not cause any collateral damage. Psocids can occasionally become an irritant nuisance to humans and other animals. Both adults and larvae are both considered pests.

Control

Control measures involve improving storage conditions and drying out infected articles so that the insects die due to desiccation. Adequate ventilation must be established to reduce the availability of suitable habitats. Use of a vacuum cleaner with proper attachments to remove debris from cracks and corners of storage areas will strongly assist in control. . Chemical treatments may include space sprays and surface sprays depending on the articles to be treated. Due to the chronic itch and allergic type reaction that some people suffer, chemical treatments are occasionally utilised by some firms to “supplement” the already effectively implemented environmental control measures.

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