PSOCIDS, BARKLICE AND BOOKLICE (PSOCOPTERA) OF BRITISH COLUMBIA

by

R. A. Cannings and G. G. E. Scudder 
Copyright © 2005 - All rights reserved

Extracted from the forthcoming publication The Insect Families of British Columbia

Description

The Psocoptera, commonly called barklice or booklice based on their normal habits, get their scientific name from the fact that the mouthparts tend to shred the food, which consists of terrestrial algae, lichens, molds and organic debris.

They are quite small insects, ranging from 1.0 to 6.0 mm in length. They are soft bodied, with the body and forewings commonly shades of brown or grey. However, domestic species which include the booklice, may be almost colourless.

The head is relatively large and mobile, with eyes variously developed. The antennae are filiform and relatively long. The unique and characteristic mouthparts consist of mandibles with a well-developed molar region, maxillae with well-developed four-segmented maxillary palps and with the lacinia being elongate, slender and with a rod-shaped ‘maxillary pick’ or ‘maxillary fork’. The labial palps are reduced and are short, with only one or two segments.

The prothorax is reduced and neck-like, but the mesonotum is greatly raised, and often extends over the pronotum. The legs have tarsi of either two or three segments, and the hind coxae usually have a rasp and adjacent tympanum involved in communication. Psocids also communicate by tapping their abdomen on the substrate.

Psocids usually have four membranous wings, which extend beyond the tip of the abdomen, and are usually held tent-like over the body at rest. However, a number of species exhibit wing reduction, and some may be wingless: occasionally there is sexual dimorphism, with males and females having a different wing condition. Wings when present have a simple venation with few cross-veins. Usually the Rs vein in the forewing is two-branched, and the M vein three-branched, while the Cu vein in the forewing is two-branched. There are one or two anal veins.

The abdomen is generally membranous, except for the last two or three segments. Cerci are absent.

The life cycle involves four to six nymphal instars, with an incomplete metamorphosis. Eggs are laid bare or encrusted with material from the digestive tract, and may be webbed or not webbed, depending on the habitat. Mating involves transfer of a spermatophore or free sperm. Vivaparity is rare, although some species are parthenogenetic.

Psocids inhabit living or dead foliage, bark of trees, ground litter, rock surfaces or they live indoors, where they can become pests of stored products or attack books.

Worldwide there are 33 families, 230 genera and over 3200 described species. More information on the biology and systematics of North American Psocoptera can be found in Mockford (1993).

References

Mockford, E.L. 1993. North American Psocoptera (Insecta). Flora & Fauna Handbook No. 10: 455 pp. Sandhill Crane Press, Inc., Gainseville, Florida.