Psocids in Illinois and Indiana | Pest Identification

Psocids

Actual Size: 1mm to 2mm in length

Characteristics: Soft-bodied, usually white or pale in color.

Legs: 6

Antennae: Yes – long and thin

Wings: The indoor variety (booklice) is typically wingless, while the outdoor variety (barklice) has wings

Habitat: Found in humid environments where mold and fungi thrive. They’re particularly fond of old books, papers, and even wallpaper (hence “booklice”)

Habits:

They feast on mold, fungi, and sometimes even pollen.
Female psocids lay their eggs in clusters, often within webbing or in papers and books.

Psocids in Illinois

Illinois provides plenty of cozy habitats for psocids. From the bustling libraries of Chicago to the quiet barns of rural Indiana, these tiny insects find their way into various environments across both states. The states’ humid summers create ideal conditions for these moisture-loving insects, especially in older buildings with less efficient climate control.

Meanwhile, in the agricultural regions, old farmhouses and barns provide perfect environments for these tiny creatures to thrive. Both states experience significant seasonal changes, which can affect psocid populations. During the humid summer months, you’re more likely to encounter these insects, while their numbers may decrease in the drier winter months.

Psocid Habitat

Psocids can be found both indoors and outdoors. Inside, they love damp basements, poorly ventilated attics, and bookshelves with old, slightly moist books. Outside, you might spot barklice on trees, feeding on algae and lichen. Indoors, psocids are particularly fond of spaces where paper and moisture meet.

In Illinois homes, this could mean:

Cardboard boxes stored in damp basements
Old newspapers piled in garages
Rarely used books on shelves in humid rooms
Behind peeling wallpaper in older homes
Around window sills where condensation forms

They’re also drawn to areas where food is stored, especially if there’s any moisture present. You might find them in pantries, particularly around items like flour or cereal that have been stored for a long time.

Outdoors, the barklice variety of psocids is more common. In both Illinois, you’re likely to spot them on:

The bark of deciduous trees like oak and maple
Wooden fences, especially in shaded, damp areas
Fallen logs in forested areas
Garden mulch or compost piles
Under loose bark or in tree hollows

Psocid Behaviors, Threats, or Dangers

Psocids are generally harmless and are considered a nuisance pest at worst – they don’t bite humans or pets. However, their presence can indicate high humidity levels in your home, which could lead to mold problems. If you’re seeing psocids, it might be time to invest in a dehumidifier. But don’t mistake psocids for bed bug nymphs! Due to their small size, they’re often confused with each other.

If you spot any psocids around your space, call your local pest exterminator right away.