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 “Oh, no! Something else is attacking our oak trees! What’s covering the limbs with a fine sheen of silk? Will they sting? Will they kill the tree?”
With our seasonal experience with buck moth caterpillars, this is an understandable reaction to anything strange associated with New Orleans’ beloved live oak trees. In this case, however, the culprits are very tiny, non-descript, harmless barklice (Archipsocus nomas), or psocids (members of the insect Order Psocoptera). As these little fellows go about their lives, they weave a very tight web close to the surface of their host tree. They are most common in New Orleans on oak and hackberry trees. Barklice are so small that one has to get nose-to-nose to the web to observe them. They range about on the bark searching for algae, fungi, pollen grains, and the like to feed upon. They do absolutely no harm to the tree and will in no way harm people or their pets - they are not “lice” that will attack your skin.
So why are there so many now? Many residents have never noticed them before. They have always been with us and their main benefit to humankind to date has been that they have functioned as great specimens for local high school kids who have to collect so many orders of insects for their biology classes! The answer to their population increase may well be tied to the same phenomenon that has inundated us with buck moth caterpillars. We can only presume that it is a cyclical rise in numbers that is dependent on proper weather conditions. We have experienced a series of very mild winters. Many species of animals and plants are controlled by the cold winter months. When the harsh weather arrives, it normally kills oodles of individuals that attempt to overwinter. These species compensate for this by having a very high reproductive rate, either producing more than one clutch of eggs per season or laying lots of eggs when they do. The selective advantage comes when, although many die, some survive. You can imagine that a critter that lays ten thousand eggs has a greater chance of having surviving off-spring than one that lays ten eggs.
Our recent mild winters have allowed many more than normal individuals of barklice to survive and breed, so the population is quite high.
The buck moths have made us very aware of animals that live on the bark and limbs of our trees. There is, however, a complete ecosystem that we should understand. There are beetles that prey on other insects, wasps that parasitize harmful caterpillars, tiny invertebrates that serve as the bottom of the food chain for who knows what. Before you become disturbed about new discoveries, and certainly before you start spraying poisons, ask yourself the question: “I wonder what they do in nature?”
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