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FIGURE 1. Barklice (Cerastipsocus venosus) nymphs are dark gray with pale yellow banding between abdominal segments. Adults and nymphs are gregarious and typically encountered as a colony (sometimes numbering several hundred individuals, as in the above photo taken on March 2007).

   
 

 

FIGURE 2. When disturbed, Cerastipsocus venosus often exhibits the fascinating behavior of temporarily scattering when suddenly disturbed, only to rejoin again as a “herd.” Not surprisingly, they are also known as "bark cattle" or “tree cattle.”

   
 

 

FIGURE 3. As nymphs mature to full size, they develop wings. Wings are light colored at first and quite wrinkled. Very young adults are almost white in color but assume their darker pattern of color in a short time.

   
 

 

FIGURE 4. Adults are about ¼ inch long and have shiny black wings, which are held in tent-like fashion over their abdomens.

   

Quick Facts

Common Name:

Barklice (a general term given to a diverse group of soft-bodied insects in Family Psosidae)

Genus / Species:

Cerastipsocus venosus

Size: Slightly over ¼ inch

Type of Beneficial:

Decomposer/Recycler

Type of Metamorphosis:

Immature stages similar in appearance to adults (i.e., simple metamorphosis)

Beneficial Stage(s):

Immature stages (known as nymphs) and adult stage

Diet:

Fungi, algae, dead bark, and other organic materials on tree trunks and large limbs

Occurrence:

Two barklice species occur across the Galveston-Houston region; Cerastipsocus venosus encountered but Archipsocus nomas more common

 

2007 . . . The Year of the Barklice—Archipsocus nomas

The calls started coming in on the Master Gardener Hotline during the mid-March 2007. Then during the last week of March 2007, several area residents submitted insect samples for identification—with each sample containing numerous small dark colored insects. The first e-mail request of the year for identification of this insect came from Rick & Lynn Vera on March 29. They provided an excellent quality image (click here to view their image).

While the Extension Office has been inundated with insect samples, we are gratified that area residents are becoming increasingly aware of the importance of trying to first identify insects before reaching in their chemical storerooms to engage in chemical warfare against insects.

Although based on antidotal evidence, we suspect that the educational enlightenments provided over the past few years by the Extension Office and the Master Gardeners is having an impact! The Extension Office certainly has experienced a yearly increase in the number of residents who visit the office to get help with identifying insects.

Two Species of Barklice in our Region

We have been alerted in our Master Gardener Training Course to be prepared to get calls during midsummer from homeowners who are alarmed about the appearance of mysterious webbing on the trunks of their oak trees! Fortunately, the webbing is not caused by webworms nor tent caterpillars, but by a harmless insect commonly known as barklice.

The species of barklice most commonly encountered in the Galveston-Houston region is brownish-colored and gregarious (Archipsocus nomas). Archipsocus nomas is a very small (less than 1/8 inch long) and soft-bodied insect. They live together underneath the protective layers of silken webbing. The silk webbing produced by this species of barklice typically appears in late summer (July and August). The webbing can completely envelop the trunk and large branches of a tree seemingly overnight.

The insect samples mentioned in the opening paragraph above were also determined to barklice. However, they were not small (adults are about ¼ inch long) and high populations were appearing in late March and not during the heat of summer. Although huge numbers would occur on tree trunks, no webbing was produced.

Basic Description

It turns out that this larger size barklouse is a closely related species of web-forming barklice. The scientific name of this species is Cerastipsocus venosus. Members of this species are noticeably larger than their web-forming cousins. Adults have shiny black wings, which are held in tent-like fashion over their abdomens.

Nymphs appear dark gray and pale yellow banding between abdominal segments. Adults and nymphs have round heads and conspicuous antennae. Members of Cerastipsocus venosus are also gregarious and typically encountered as a colony (sometimes numbering several hundred individuals, as in March 2007).

Each colony typically contains a mixture of nymphs and adults. As nymphs mature to full size, they develop wings. Wings are light colored at first and quite wrinkled. Very young adults are almost white in color but assuming their darker pattern of color. Adults are “reluctant” to fly but this is the primary means of dispersal {refer to Figure 4 at the bottom of the article on Barklice (Archipsocus sp.)}.

Behavior

The term "lice" as part of the common name of these tree dwellers is quite misleading as these insects are neither parasitic nor louse-like in appearance. Upon being informed of the identification of this insect, the typical response of a gardener is a widening of the eyes and other momentary indications of being aghast! Our Galveston County Extension Horticulture Agent advises us to precede the identification with a notation of  “Congratulations, you have beneficial insects in your landscape!”

When disturbed, Cerastipsocus venosus exhibits the fascinating behavior of moving en masse, somewhat like a flock of sheep or herd of cattle. They may also temporarily scatter when suddenly disturbed, only rejoin again as a “herd.” Not surprisingly, they are also known as "bark cattle" or “tree cattle.” Barklice are most often noticed on smooth-barked shrubs and trees such as crape myrtle and on oaks although they occur on a variety of hardwood ornamental plants (we have seen them on Bradford pear).

Beneficial Status

You may wonder why barklice are being included as beneficial insects. As scavengers, they perform a valuable function in consuming excess accumulations of fungi, algae, dead bark and other materials that occur on tree trunks and large limbs–in effect, they function as “Bark Maids” to help clean the bark of undesirable inhabitants. Barklice do not eat leaves or the bark of the tree, nor do they damage the tree by boring into the bark.

No control measures are recommended for these insects. Treatment is not recommended as the barklice are providing a beneficial service by helping Mother Nature to keep the bark clean and tidy!

Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.

 

This web site is maintained by Master Gardener Laura Bellmore, under the direction of William M. Johnson, Ph.D., County Extension Agent-Horticulture & Master Gardener Program Coordinator.

All digital photographs are the property of  the Galveston County Master Gardener Association, Inc. (GCMGA) © 2002-2006 GCMGA - All Rights Reserved.