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| 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."
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| Woolly aphids on a log - Mark Bower |
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| 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."
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| 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.
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| 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..
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Woolly aphids- Courtney Reece
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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.