The chatatenmushi booklouse isn’t only found in books!!!

Psocids or booklouse

Psocids or booklouse

I learned about a common bug found in every home today from the Japanese NHK TV programme. It is called chatatenmushi チャタテムシ(茶立虫)in Japanese (why do so many horrid bugs have such kawaii Japanese names??) or booklice / psocids in English.

Found in much the same places as dustmites, the booklouse is found in every home in locations like carpets and tatami mats. 22% of Japanese are allergic to booklice carcasses and poop.

The species known as booklice received their common name because they are commonly found amongst old books—they feed upon the paste used in binding.

Psocids are small, scavenging insects with a relatively generalized body plan. They feed primarily on fungi, algae, lichen, and organic detritus. The booklouse feeds on a kind of book fungus, spores of which is commonly found in house dust that settles on books and on book fungus seen as book spots and stains in old books and papers. Book lice have chewing mandibles, and damage books and papers.

Besides damaging books, they also sometimes infest food storage areas, where they feed on dry, starchy materials. So be sure to clean out your larders often. They are scavengers and do not bite humans.

Some species are wingless and they are easily mistaken for bedbug nymphs and vice-versa. Booklice are found in carpets along with dustmites, and can be vacuumed up easily.

Booklice range from approximately 1mm to 2mm in length (1/25″ to 1/13″). Control methods are similar to control of dustmites involving meticulous vacuuming of carpets and tatami and keeping low humidity in the home. In fact, booklice cannot survive when humidity falls below 40%. Keeping a PVC clear folder over your books is an easy way of keeping the bugs from breeding in your books (just wipe off the dust periodically).

Some species have wings (see photo of winged variety below), others are wingless. Some species can spin silk from glands in their mouth. Psocids lay their eggs in minute crevices or on foliage, although a few species are known to be viviparous. The young are born as miniature, wingless versions of the adult. These nymphs typically molt six times before reaching full adulthood. The total lifespan of a psocid is rarely more than a few months.

Booklouse eggs take 2 to 4 weeks to hatch and can reach adulthood approximately 2 months later. Adult booklice can live for six months.

To sum up, here’s a quote from the Booklice article,

“Booklice feed on molds and will overrun cereals and similar materials that support mold growth. Their presence, therefore, is a nuisance and can render some foods unfit. The starchy paste of wallpaper and books also can support mold growth or may be attacked directly by booklice. Outside of annoyance, their damage is insignificant.” — Booklice.

More info below…


Facts, Identification & Control
Latin Name
Order Psocoptera

There are more than 200 species of psocids (often pronounced “so-sheed”) in the United States. Most psocids are tiny insects. Depending on the species, the size ranges from 1 to 6 mm. The color of psocids varies according to the species. Psocids that live outdoors often have wings. Psocids that invade homes usually have very small wings or no wings at all.

Psocids have chewing mouthparts, but they do not bite people or pets. When they invade kitchens, they can contaminate open packages of food.

Behavior, Diet & Habits
Psocids are tiny insects that live in damp environments. They eat mold and mildew. Some people call them barklice or booklice. The name barklice probably comes from the fact that outdoors they gather under the bark of trees. The name booklice comes from the fact that they gather on moldy books in damp homes. Experts think that the sizing and starch in the bindings of books supports mold growth in humid environments.

Psocids invade areas where there is dampness and mold, like basements and crawlspaces. They also infest areas where a plumbing leak causes mildew or mold to grow. Psocids have infested bath traps with leaking or sweating pipes. They have also infested air conditioning drain lines. They feed on mold in their damp environment.

Psocids often seem to appear suddenly. This may be because they are so small that people do not notice them when there are only a few around. Some people think psocids look like tiny termites.

Psocids cannot retain water in their bodies, so they are sensitive to changes in humidity. A key step in controlling psocids is reducing the humidity in their environment. When the humidity is low, the psocids will die. If the humidity stays low, they will not reinfest.

The females lay eggs in the spring and summer. The immature insects are called nymphs. They look like the adults but have no wings.

Signs of a Psocid Infestation
The main sign of psocids is the sighting of the psocids themselves on surfaces or in products.


Make a careful inspection to find the moisture sources. If psocids are active in the kitchen, start the inspection under the sink. Empty the cabinet if necessary. Inspect every area that has plumbing. In the bathroom, there should be a trap door near the head of the bathtub for access to the pipes. Inspect tile walls carefully. If grout is missing, mildew can grow behind the tiles.

There can be other moisture sources besides the plumbing. Look at the gutters and downspouts. Make sure they are not blocked. Downspouts should drain away from the foundation.

Check the crawlspace vents. They should be open in warm weather. If there is moisture on basement walls, specialists at the home store can recommend ways to waterproof them. A dehumidifier can also help reduce moisture in a basement.

The local pest control professional can select techniques that are effective in the situation.

More Information
Although people call them booklice, psocids are not really lice and do not feed on blood. They are insects in the order Psocoptera.


References and sources:

NHK Asaichi TV programme



Wikipedia “Psocids / Psocoptera



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