Aphids, Scale Insects, Thrips and Barklice of Columbia County, Oregon

Aphids and Scale Insects are true bugs which feed on the sap of plants and trees. Thrips and Barklice are primitive insect families considered either part of the True Bugs or closely related to them. All of these insects are small and often found congregating on plants in large numbers.

Aphids (Aphidoidea)

Aphids are small insects with soft bodies that feed in large groups on plant juices. They are most closely related to “spruce aphids” and then scale insects. Some aphids feed on the same plant all year round while others spend the summer on one type of plant and the winter on another.

The aphids here are roughly organized by the plants they’re found on, which is the best way to ID them. Identification can best be done using the aphids page at Influential Points and Aphids on the World’s Plants.

Spruce Aphids (Adelgidae)

“Spruce Aphids”, also known as “Pine Aphids”, differ from true aphids in lacking cornicles or cauda sticking out the back of the body. They feed on the needles and twigs of conifers like spruce or pines. Because at different life stages they have varying appearance and may be covered by a gall or waxy excretion, Spruce Aphids are often ID’d by their effect on plants (drained needles and galls on branches) rather than by seeing the bug itself.

Scale Insects (Coccoidea)

Also called “mealy bugs”, the females of this species are soft limbless bugs that hide under a protective scale on their plant host. They often remain unnoticed until they produce a large eggsac behind or above their actual bodies. Males on the other hand are tiny winged fly-like bugs that can travel between the plants to fertilize the females. Some species have a mutualistic relationship with ants. Identification is often difficult and depends on identifying the host plant.

Thrips (Thysanoptera)

Extremely small, slender, soft-bodied bugs, often with thin fringed wings that they rarely use. Have sucking mouthparts that most species use to suck plant juices, though a few are predators. Larva are often brightly colored while adults are drab and dark. Thrips are difficult to find information on – there are dozens if not hundreds of species in oregon, but only a few of the most well-known ones are covereed here.

Barklice and Booklice (Psocoptera)

Considered the most primitive of all true bugs, barklice over 250 million years old have been found in the fossil record. They are very small winged bugs (though many drop their wings) with amusingly bulbous eyes. In nature they feed on fungi and algae on trees, though some have become stored grain pests or enjoy the paste on book bindings. They are a close relative of parasitic lice.

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