Learning Center

These tiny little bugs are often mistaken for fleas because the males (pictured on the right) appear to hop around when you see them on the floor or on the patio slab. They are not strong fliers and will only go a very little way before they land, so it looks a lot like they are hopping! The female (on the left) does not have wings and must crawl wherever she wants to go. There are several varieties of psocids in North San Diego County, but the ones that we get the most calls on are the three types that feed on molds that are associated with plants or moist wood. Psocids (pronounced “ so – sids”) come into the house when things start to dry up outdoors and sometimes they appear in great numbers.

Normally when you see several psocids on the floor it is because they are coming from the outside, usually under a door. You should check the bottoms of all exterior doors, especially sliding glass doors, to make certain that they are properly sealed with a door bottom, brush, or a weather strip.  Remember that there are other bugs that can come inside in the same manner.

If you are seeing large numbers of psocids on counters, tables, or in the pantry, you should check for moldy food or for a moisture condition inside the structure.  I often find psocids in fungus-damaged wood, usually in the eaves or in a woodpile, but occasionally they show up indoors as the indirect result of a leaky shower pan in the upstairs bathroom or because of a leak in a roof or a downspout. But they are much more prevalent in mulch and bark ground cover outside if conditions are moist enough for mold to develop.

The best way to control those psocids that are coming in from outside, is to control the moisture conditions that allow mold to develop. Outdoors, the problem normally takes care of itself here in North County with our prevalent sunshine and dry weather, but if you overwater consistently you will be inviting psocids for dinner. Their function outdoors is to control microflora by keeping certain kinds of molds from growing unchecked. This is especially useful in tall fescue lawns and in cane and other tall grasses, so psocids serve a very useful function in that regard. When they come inside the house you will find that a vacuum cleaner is your best tool for psocid control!

There are two types of psocid that are commonly referred to as Book lice. One of them looks like a tiny red dot, and the other is usually oval-shaped and yellowish in appearance. If you enjoy reading old books as much as I do, you will have seen more than a few Book Lice trying to avoid your scrutiny as they move across a page. They are very tiny, much less than a third of the size of the outdoor varieties of psocids, and they crush easily if you touch them.

Referring to psocids as Book Lice, or Bark lice can be a bit misleading, because psocids do NOT bite or feed on books or bark and, unlike true lice, they do not feed on people or animals. Body Lice, Bed Lice, Head Lice and other pests that feed on blood are not related in any way to psocids. In fact psocids are not really lice at all and they neither bite nor are they known to transmit any diseases.