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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). |
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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.” |
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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. |
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FIGURE 4. Adults are about ¼ inch long and have shiny black wings, which are held in tent-like fashion over their abdomens. |
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Quick
Facts |
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Barklice (a general term given to a diverse group of soft-bodied insects in Family Psosidae) |
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| Size: | Slightly over ¼ inch |
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Decomposer/Recycler |
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Immature stages similar in appearance to adults (i.e.,
simple metamorphosis) |
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Beneficial
Stage(s): |
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Diet: |
Fungi, algae, dead bark, and other organic materials on tree trunks and large limbs |
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Occurrence:
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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.
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