Fungus Gnat on Butternut.

Mark Bower found some butternuts at the base of the hillside but we have never found the tree.  Butternuts are also called white walnuts, Juglans cinerea, a reference to the color of their wood.  They grow in the Eastern United States, and we are at the very western edge of their range.    They tend to grow in small numbers along water and well drained slopes and the only one we have found in the past was a blow down across a trail.  We decided to plant some of the nuts along the creek.  Since they don't tolerate shade well, a barren riparian border should be perfect.

Fungus gnat larva with mycelia, walnut husk fly larva and unknown brown pupa cases.

These butternuts had been down a while and their husks were starting to blacken.  While inspecting one of them,  I found some tiny 2-3mm hair-like strands that I mistook for fungal mycelia until under magnification I saw that they moved as seen in this video.  I showed them to Chris Barnhart and he identified them as "fungal" all right, but actually the larvae of the fungus gnat.


Technically walnuts are not nuts but are classified as a drupe because of the fleshy covering on a hard pit or stone.  Other flowering plants classified as drupe producers include the almond, cherry, apricot, peach, nectarine, plum and our beloved coffee.   Like our common black walnuts, the product we treasure is not the flesh but the nut inside.  As the flesh breaks down, fungal hyphae frequently contribute to the disintegration, providing a home for the fungus gnat.

Sciarcidae - 2mm long + antennae

Like so many interesting tiny critters we find, this larva is a fungus gnat, destined to Google obscurity by its predominate links to "How do you get rid of fungus gnat larvae?" when I am trying to find more about its interesting lifestyle in soil and rotting debris.  Most are a few millimeters long and get no respect, like fungi and the things that eat them.  Without them we would be miles deep in dead and dying plants and trees!  Wikipedia to the rescue!

Most fungus gnats occur as larvae feeding on fungi in the soil, emerging as adults to walk around and weakly fly on occasion.  They carry mushroom spores and are incidental pollinators.  A few species of larva are predatory, killing small invertebrates with an acid fluid (mostly oxalic acid) secreted by labial glands.

The gnats occasional bother us larger bipeds by flying in our faces and they may be confused with bathroom flies.  Numbers of them in your house may indicate over watering of house plants.  As you might expect, there are a number of toxins developed for their elimination in greenhouses.

Most organisms tolerate winter by either freezing (with the help of antifreeze chemicals they produce) or avoiding it.  Some fungus gnats produce antifreeze proteins but Excechia nugatoria  has it both ways.  The head and thorax are protected by the production of (your new word of the day) noncolligative antifreeze proteins (NAPs) while the abdomen freezes, thus reducing evaporative water loss.  How cool is that!

Fungus gnat larval procession

Finally, here is a video from Thailand of a procession of larvae forming a column.  This is a rare occurrence but when found the people keep the larva at the head of the column as the "King Worm" for good luck (theirs, not the larva's).