Booklice (Barklice)

Description and Identification

These tiny insects grow around 1-2 mm (1/25 – 1/13 inch) in size, having a soft pale gray to brown body. The head and abdomen are large, while the thorax is narrow and not as visible. There are 9 clear segments in their abdomen but no cerci (pair of spine-like appendages present on the last abdominal segment in many insects). They somewhat resemble termites when seen through a magnifying glass.

Booklice also have large compound eyes, three ocelli, and a pair of long segmented antennae. Their slender legs are adapted more for jumping, unlike the parasitic lice, which have legs more suitable for gripping.

Overall color and appearance may vary among individuals within the same species. Some may have wings, while others may lack them. Other apparent differences may be related to the ovipositor’s presence and the thorax’s shape.

There may be some variation in the development of the bristle-like hairs (setae) on their body. It is still unknown how such differences may be helpful. Still, their function does not seem to be the same as similar variations on other insects like aphids.

Usually, the indoor booklice are wingless, with a remarkable resemblance to bedbug nymphs. Outdoor species often have wings with a simple venation pattern. The four wings are held over the body in a tent-like manner.

Some species have special silk-spinning glands inside their mouth, which they use to cover large areas of tree branches and trunks in dense silk.

Distribution: Throughout the world

Habitat: Indoor – in old books and wallpapers; moldy, damp, dark places around the house; Outdoor – in tree barks, bushes, and under rocks

Do They Bite/Sting: No

Lifespan: Up to 6 months

Predators: Other insects, arthropods, and small vertebrates

Behavior and Characteristics

Diet and Feeding Behavior

In homes, they are considered pests as they feed on whatever starch-based item they can find, including stored foodgrains, cereals, starchy book bindings, and even wallpaper glue and furniture. The booklice get their name because they are usually found around old books. One species,  Liposcelis bostrychophila, is a common pest found in stored food.

However, most of the Psocoptera species are found outdoors, in woods and forests, and living in tree barks. These species are referred to as barklice.

They have mandibles adapted for chewing, with an elongated central lobe modified into a rod. The insects use this rod to stay in place while they use their mandibles to scrape off food.

Life Cycle

1. Egg Stage

The females lay up to 60 eggs singly or in clusters, during summer, in small holes in the ground or foliage. They may cover the eggs with debris to keep them safe. They take around 2-4 weeks to hatch. The number of eggs produced goes down during the colder months, and they take much longer to hatch.

Though mostly egg-laying, there are a few viviparous species of booklice,

2. Nymph Stage

The newly-hatched booklice look like smaller versions of the adults, except they have no wings. They usually have 6 molts over a few weeks.

The nymphs of the species Psilopsocus mimulus are known to make their own burrows in wood instead of living in existing holes. Other insects often use the burrows they make.

3. Adult Stage

The nymphs reach adulthood about 2 months after hatching. Many booklice can be parthenogenic, meaning the females can reproduce independently in certain conditions. The development of males can vary between populations.

Their life cycles heavily depend on temperature and humidity.

Getting Rid of Booklice

The best way to drive booklice away is to eliminate the excess humidity, which removes the mold that attracts them. Using dehumidifiers, keeping your windows open to let in some light and air, leaving some airspace under potted plants, and vacuuming any areas they are likely to infest can help. Keeping the relative humidity levels below 58% makes the conditions unfavorable for booklice to survive for more than a few weeks.

In most cases, insecticides or chemicals are not necessary. Still, there are products and sprays available for large infestations.