Wednesday, October 14, 2015

Lacewing Eggs

Green lacewing larvae, a.k.a. aphid lion - REK
Barb's "tiny something"
This story began with a chance finding of a tiny "something." Barb was working with Lisa Bakerink salvaging swamp milkweed along South Creek before  the concrete was removed to improve storm water drainage. They were joined by Cody Stice from the Department of Public Works who came out on his own time to help. He spotted some tiny threads on the milkweed leaves and Barb brought a leaf fragment home for me to see.  I required a magnifier to see the specimen that was bent into a curve from the ride home but she said they were all were originally sticking straight 90 degrees off the edge, horizontal to the ground.  After a few wrong guesses I sent the picture to Chris Barnhart who identified it as a lacewing egg.

Green Lacewing species - Jon Rapp
Green lacewings (Chrysopa sp.) are beautiful and delicate creatures that are the gardeners favorite.  They and their larvae are frequently predators of garden pests such as small caterpillars, mealybugs, psyllids, thrips, mites, whiteflies, and aphids.

Lacewing Eggs - John Meyer
Chrysoperia pupa - nbair.resv
The female produces single eggs, each on a silk strand off a leaf edge which presumably reduces predation.  In a few days a larva emerges, eating everything it finds including any unfortunate siblings.  It will munch its way through three progressively larger instar stages before pupating in a loose silk cocoon.  Adults overwinter in leaf litter.

Aphid lion contemplating dinner - REK
The larvae would probably not be considered beautiful by even their mothers.  Also known as aphid lions, they resemble a prehistoric alligator with a bad haircut and any student would guess they are predators based on their fierce pointed jaws.  They grab their prey and inject a paralyzing venom before sucking out their juices, leaving behind the empty skin as they grab the next victim.  I filmed this video to document their appetite for aphids.  Three rapid sequence photographs below show an aphid going from happy to sucked dry.

Grabbing a quick bite
First taste of a fat morsel.......
..... now shriveled down to nothing.
Many companies offer lacewing larvae in bulk to populate your garden as a treatment for aphids.  However they will eat anything they get in their pincers including butterfly caterpillars that we might treasure.  As an example:
"A 2007 Monarch Lab study determined that C. rufilabris larvae depleted 35 eggs from milkweed in 24 hours, seemingly unaffected by the monarch’s toxicity."
So are lacewing larvae good or bad?  Almost any time you hear that question the answer is "It depends."

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