Lacewings at Light, and their eggs

2013 January 9

When I left the garage ceiling light on and the door open on the morning of May 19, 2012, the single most common species drawn to the light was lacewings. There were a few dozen of them, all over the ceiling.

If I had doubted that they were common before, I have no doubts now. They really appear to be dominating the aphid-eating niche, I find way more lacewings than lady beetles these days.

Which is why it wasn’t a complete surprise when, on July 2, 2012, Sandy told me I needed to check out the interesting eggs that she’d found laid on the ceiling of our little pickup truck (which had been parked in the driveway with the windows partly open for a couple of days).

They were a long row of nearly fluorescent-green eggs, each about a millimeter long and spaced a couple of centimeters apart, that seemed to be hovering in mid-air about a centimeter below the truck ceiling. If we look very closely, it is just possible to make out the thin filament that the egg is hanging from.

This filament is characteristic of lacewing eggs. The reason for it appears to be this: Lacewing larvae like to eat aphids, so the adults normally[1] try to lay their eggs near aphid colonies. But, aphid colonies are often guarded by ants, who essentially herd and “milk” them for the honeydew that they secrete. The ants will kill and eat any other insects or eggs that they find near the aphids, and lacewing eggs would be completely defenseless against the ants. So, the lacewings have evolved these filament stalks, minimizing the chance that the ants will actually stumble across the eggs. Or, if they do hit the filament, not realize that there is an egg at the end of it, and so ignore it. Presumably, once they hatch out, the resulting larvae are agile enough to dodge the ants (or, once they get big enough, maybe even eat the ants first, like their relatives the antlions).

Which seems to me to be a very elegant, efficient solution to what otherwise would be a terrible problem for the lacewings. And may be one of the reasons why they are more successful than the lady beetles, at least locally.

One last thing: Lacewings overwinter as adults. As evidence of this, here is a picture of one on the outside of our kitchen window on November 11, 2012 (which is very, very late in the year for most of our local insects to be flying about!)

So, all those lacewings that came to the light in the spring had been hiding out as adults all winter somewhere. The question is, where?

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[1] I don’t think our truck is infested with aphids, but as noted, we have a lot of lacewings around these days. Some are bound to get confused and lay their eggs in untenable places from time to time.

One Response leave one →
  1. Eryca permalink
    May 9, 2013

    they are so cool i have one

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