Barking Up the Tree: Barklice

The sighting of a web usually indicates the presence of one of the many species of spiders living in Wakulla County. While some spiders do not use webs to trap their meals, most do in one of several distinctive forms.

The petite strands are closely monitored by the patient arachnid. When a careless insect blunders into the trap, the spider reacts quickly to secure the nutritional resource.

From a tactical standpoint, the webs are positioned to maximize the prospect of capturing a prey. Occasionally a web will be seen which does not meet the logical criteria for seizing a meal.

Barklice are one of the lesser known native insects which use a web system to festoon tree trunks and branches with no intent on capturing anything. Many entomologists believe the webs are a form of protection from predators which would quickly consume the soft bodied nymphs and adults.

A member of the Psocoptera insect order, it is distantly related to parasitic lice (Phthirapters) which have plagued humanity and other creatures with blood for many millennia.

These small insects which mature to about half an inch in size are also related to a species known as booklice. With a preference for bookbinding paste, these insects can be a problem for anyone who values old tomes. 

While the appearance of a barklice population on a tree might be startling to an observer, the insects are not harmful and require no control messures.

Fortunately, the much larger barklice consume lichens and algae found on tree bark. Live oaks and cabbage palms are a favorite local hangout for this bug as these trees offer food and protection.

Their lifecycle begins in spring when mature females which have survived the winter begin laying eggs. They are laid individually or in groups and are covered with debris for the short incubation. 

As the weather warms from March to June, the barklice population slowly builds. The hatchlings quickly progress through several instars or distinctive life stages before reaching adulthood.

As summer progresses into autumn, the populations continues to build. Females fly to uncolonized sites nearby to leave more eggs and produce more nymphs.

Reaching a critical population mass, this is usually the time when these harmless insects are suddenly noticed by homeowners. Sometimes the casual observer will notice a new dark mass on the surface of a tree.

The gregarious nymphs numbering in the hundreds will form a shifting shape as they graze while tightly packed on the bark’s upper level of detritus. If suddenly approached they will scatter, only to reassemble when the perceived threat ends.

With the appearance of a tiny drill team, they will sometimes march in single file to new dining sites on the tree. After arriving, they again form an irregular splotch.

When they produce a web, it will cover multiple square yards of a tree’s trunk and sometime the lower branches. The silky material is produced by a gland in the mouth of the barklice.

The shimmering white sleeve will last as long as these insects occupy it.  None of the barklice’s activity does any harm to the tree so controls are not necessary.

As autumn fades to winter these insects’ numbers drop dramatically. They fall prey to cold weather and predators preparing for winter’s privations.

Fortunately, none of the approximately 5,500 member of this worldwide insect order are considered threatened. Fossil records indicate they have been around almost 300 million years, so even the winter of 2020/21 will likely be only a brief interlude in their activities

About the author
Les Harrison

Les Harrison is a longtime resident of north Florida, having attended public schools in three counties. He has a Bachelor Degree from the University of Florida in Journalism and a Master’s of Science from Auburn University in Agricultural Economics. He is the author of more than 2000 newspaper and magazine stories and journal articles. During his career, he held positions in private, government and educational (university level) sectors. He holds the title of Extension Agent Emeritus. He can be reached at harrison.gl@gmail.com.

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