Saturday, April 26, 2014

Lace Bugs

On the Bull Mills botany field trip last Saturday, led by Justin Thomas* someone noticed some tiny spots on the underside of buckeye leaves on one tree.  With a hand lens we could make out tiny winged insects but no further details.  Occasional buckeyes along the drive had similar infestations although there was not apparent damage to the leaves at present.

I showed enlarged macro photographs to Dr. Chris Barnhart who identified them as lace bugs.  I began thumbing through page after page of lace bug pictures in - there are over 2,000 species world wide - with no luck.  Finally in a moment of biological brilliance, I Googled "buckeye lace bug" and immediately found identical pictures of our insect ... a "buckeye lace bug."  Who knew!?

Lace bugs are tiny insects (2–10 millimetres or 0.08–0.39 inches) in the family Tingidae.  They are Hemiptera, defined by their specialized mouth parts used for sucking out plant juices.  Our buckeye lace bugs measured 3.5 mm in length.

Dense collection of lace bugs
The buckeye lace bug, Corythucha aesculi is a North American native which co-evolved with the native buckeyes.   It was first reported on yellow buckeyes by William Stehr in 1938, appropriately enough in Ohio.  They overwinter under the bark of oaks and other trees, emerging after a few warm days to swarm on the emerging buckeye buds.  They will feed on the same leaves through their life cycle, raising their offspring and eventually their grandchildren on the same tree.

Copulation occurs soon after emerging and a few days later they begin laying their eggs on the underside of leaves.  Stehr found that the females produced an average of 178 eggs apiece.  There are two broods a year, the spring group being more successful as the leaves are healthier and juicier and there are fewer predators around.  The summer brood will produce the adults that overwinter under nearby bark of other trees as the buckeye bark doesn't provide adequate shelter.  How they find a host tree the next year is unknown.
From  the original paper by William Stehr
Unless they are on the only buckeye in your yard, they don't cause significant problems in nature.  As usual, the thousands of eggs will produce hundreds of early instars, most of which won't survive.  Many will feed birds and a wide variety of insects, especially ladybugs.  And the cycle goes on.  Lets hear it for the humble, odd looking, often overlooked lace bug.  The world would be a less interesting place without them.

*  Justin Thomas and his wife Dana are experienced field botanists and together form the Institute of Botanical Training which provides field-based botanical services and comprehensive workshops for persons seeking on-the-job plant identification skills.

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