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A Webbing Barklouse, A Psocid, Archipsocus nomas Gurney (Insecta: Psocoptera: Archipsocidae)

Donald W. Hall

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences.

Introduction

Archipsocus nomas Gurney is a communal web-spinning barklouse. During some years they make extensive silken webs that often cover the trunks and branches of trees in the southeastern US. The webs are believed to protect the barklice from predators. The webs are unsightly, but neither the barklice nor the webs cause any harm to the trees. These insects are sometimes referred to as "tree cattle."

Distribution

Webbing barklice are found along the Gulf coast from Texas to Florida and along the Atlantic coast north to South Carolina.

Description

The eggs of A. nomas are oblong, wider at one end, and gray or white in color. Nymphs and adults are soft-bodied insects with chewing mouthparts and long filamentous antennae. They lack cerci. First instar nymphs have eight antennal segments, but the full complement of 13 segments is gained at the first molt. The number of nymphal instars has not been determined for A. nomas. In Archipsocus floridanus, a closely related species, females have six, and males may have from four to six—but most commonly five. Adults are darker in color than nymphs. When winged, the wings are membranous and held roof-like over the body. Winged females may be either long or short winged. Winged males are short winged.

 

Figure 1. Young Archipsocus sp. nymphs.
Figure 1.  Young Archipsocus sp. nymphs.
Credit: Lyle Buss, UF/IFAS

 

 

Figure 2. Late instar Archipsocus sp. nymphs.
Figure 2.  Late instar Archipsocus sp. nymphs.
Credit: Lyle Buss, UF/IFAS

 

 

Figure 3. Archipsocus sp. winged females.
Figure 3.  Archipsocus sp. winged females.
Credit: Lyle Buss, UF/IFAS

 

Life Cycle and Biology

Colonies of A. nomas are rare during the winter (December–February in central Florida) and are concentrated in live oak (Quercus virginiana Mill.) hammocks and stands of cabbage palms (Sabal palmetto [Walter]) where they probably are best sheltered from killing frosts. During this time, colonies are composed primarily of adults with a few late instar nymphs. In the spring, eggs are laid singly or in groups and covered with debris or sometimes by feces. From March to June, colonies become more frequent, and from July to October, colonies rapidly increase in both number and size. The long-winged females are usually observed only during this time of maximum colony proliferation. Nymphs and adults probably feed primarily on lichens. By early December, populations have been greatly reduced by frost, and the webs begin to disintegrate due to weathering. Because the barklice are not harmful, control measures are not recommended.

 

Figure 4. Archipsocus nomas Gurney silken web on Ilex sp.
Figure 4.  Archipsocus nomas Gurney silken web on Ilex sp.
Credit: D. W. Hall, UF/IFAS

 

 

Figure 5. Tree trunk covered in webbing produced by Archipsocus nomas Gurney.
Figure 5.  Tree trunk covered in webbing produced by Archipsocus nomas Gurney.
Credit: Douglas L. Caldwell, UF/IFAS

 

Selected References

Borror DJ, Triplehorn CA, Johnson NF. 1989. An Introduction to the Study of Insects. Philadelphia, PA: Saunders College Publishing.

Mockford EL. 1953. "Three new species of Archipsocus from Florida (Psocoptera: Archipsocidae)." Florida Entomologist 26: 113–124.

Mockford EL. 1957. Life history studies on some Florida insects of the genus Archipsocus (Psocoptera). Gainesville, FL: Bulletin of the Florida State Museum (Biological Sciences) University of Florida. 1: 253–274.

Mockford EL. 1987. Order Psocoptera. In: Stehr FW, ed., Immature Insects. Dubuque, IA: (Vol. 1) Kendall/Hunt Publishing Company.