Flying Lint

Woolly aphid - Mark Bower

The last few days we have been seeing tiny white fluff drifting through the air.  Watching closely you can see it gradually change altitude or direction.  These are woolly aphids, members of the Eriosomatinae subfamily.  In flight they have been likened to "flying mice" and are given nicknames like "angel flies," "fluff bugs,""fairy flies,"and "ash bugs."  My favorite is "flying lint."

Woolly aphids on a log - Mark Bower

Ready for take-off - Mark Bower

Mark Bower introduced me to them years ago when he found a log with clusters of tiny 2 mm light blue winged insects.  Looking closely they even appeared to be covered in powder.  He nailed the diagnosis of woolly aphids before I could even get back to my computer.

Woolly aphids (WA) are members of
Eriosomatinae subfamily, a branch of the aphid family, Aphididae.  According to Wikipedia:

"Woolly aphids are sucking insects that live on plant sap and produce a filamentous waxy white covering which resembles cotton or wool. The adults are winged and move to new locations where they lay egg masses. The nymphs often form large cottony masses on twigs, for protection from predators."

Naked WA - REK

I caught this one by hand and by the time I transferred it to a bug box, its wax had rubbed off and it couldn't take off, making it willing to pose.  This one was also 2mm long although it looked larger when it had all its wax.  You can see a video here of another one under the microscope as I wiped off some of its wax.

Some WA specialize on one variety of plants while others may lay eggs for their larvae on a different species than the ones adults feed upon.

Insect trash talk - Mark Bower

The woolly apple aphid is a major economic pest in orchards.  Like the cedar apple rust galls that depend on cedar and apple trees in close proximity to support their two year life cycle, the apple aphid requires elm trees for the egg and larval feeding phase while the adults attack apple trees.  Woolly aphids have a needle-like stylet mouth which they use to penetrate buds, bark, leaves and roots to suck up sap.  Many produce a sticky honeydew which then can support the growth of a sooty mold on the fruit.

Many woolly aphid species are accidentally introduced invasive species.  An example is the hackberry wooly aphid, Shivaphis celti, which was found in the south in the 1990's and is now also a problem in California.  Although it doesn't damage the tree significantly, it is a pest because its copious honeydew excretions create a sticky mess which in turn feeds a blackish sooty mold on leaves and anything under infested trees.. 

Woolly aphids- Courtney Reece

The reproductive cycle of these woolly aphids which use two host plant species is complex, as explained by this Bugtracks article.  Most species emerge as all females in the spring and reproduce by parthenogenesis (without mating between the male and female).  They give live birth (no eggs) several times in the spring and summer on the primary host plant.  Winged forms then fly to the secondary host plant, reproduce again and eventually give birth to winged males and females which fly off to a primary host plant and mate, starting the whole process.  If you think this confuses you, imagine being the aphid figuring out your family history.

Not all woolly aphids are warm fuzzy creatures.  The larvae of the woolly beach blight aphids gather together when disturbed and poke their posteriors in the air, an aphid version of "mooning."  It looks like dancing as seen in this video.  This is no hollow threat as they are shown under the microscope to stab predators with their stylet mouth parts that are usually reserved for penetrating wood to sip sap.  I guess if you usually drill into beach trees with your mouth, penetrating a predatory moth larva is a piece of cake.

The very complete source of information on aphids is aphidsonworldsplants.