Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
7/30/01
Contacts:
Donald Lewis, Extension Entomology, (515) 294-1101,
drlewis@iastate.edu
Del Marks, Continuing Education and Communication Services,
(515) 294-9807, dmarks@iastate.edu
Yard and Garden Column for the Week Beginning Aug. 3
Insects of Lace
By Donald R. Lewis
Extension Entomologist
Iowa State University Extension
When two things have similar or similar sounding names, the usual outcome is confusion or misunderstanding. So it is with many insect names that look or sound the same. There are more than one million known species of insects but a much, much smaller number of available common names. So it is that one generic name is applied to several unique species, or that many different insects end up with similar names.
A case in point is insects that look like lace. Many insects have parts, usually the wings, that resemble lace. Either the lines inside the wings (veins) or elaborately sculptured ridges on the body surface look like miniature versions of the familiar, open-woven fabric made of thread or yarn and used for doilies and curtains. Two common insects in particular, the lacewings and the lace bugs, fit this description. Keeping them apart in spite of their similar names is important to appreciating their varying functions in the ecosystem.
Good guys first
Lacewings may be familiar to you because of their occasional appearance around the back porch light. When they are not being pulled off track like a "moth drawn to a flame" they are common in fields, gardens and landscapes. The most common species are called green lacewings because of their pastel green color and clear, membranous wings crisscrossed with numerous green veins and cross-veins. The soft, elongate body is about three-fourths of an inch long, and the wings extend past the tip of the abdomen. One common species has large beady eyes that look like shiny drops of gold.
Other lacewings are brown in color, slightly smaller, but otherwise similar in appearance. Appropriately, these are called brown lacewings. Brown lacewings are not as common in crops or gardens as are green lacewings.
Lacewing larvae are nothing like the fragile adults just described. They are elongate, slender and mottled gray with tufted tubercles along the sides of the abdomen. Further, they are ferocious, cold-blooded predators in the garden and landscape. They follow after aphids and other small insects until they overtake them and then, using enlarged sickle-shaped mandibles at the front of the head, they puncture the prey and suck out the internal fluids.
Predators such as lacewing larvae are good for the garden. These larvae are beneficial natural enemies that attack aphids and other potential pests reduce the size of the population and subsequently the amount of plant damage that occurs. This, in turn, can reduce our need to use insecticides.
Lacewing larvae grow to about three-eighths of an inch in length before they spin a silken cocoon and transform to the adult stage. Development from egg to adult takes about a month and several generations occur each summer.
Green lacewings are available for sale from commercial sources. Eggs can be purchased for release in the garden to augment the existing populations of these beneficial predators.
Lace bugs: Tree feeding pests
The name lace bug sounds similar to lacewing but almost everything about these two insects is different. Lace bugs are plant feeders that feed on sap from the leaves of trees. They are commonly found on the leaves of hackberry, sycamore and oak trees. Lace bug growth and development occurs throughout the summer though it is typical to notice the damage and the adults in August and September.
Lace bugs feed on the underside of the leaves. They pierce the leaf with their sucking mouthparts and cause characteristic pale yellow, scorched or "bleached" discoloration on the upper leaf surfaces. The underside of heavily infested leaves becomes speckled with small, black, shiny "varnish spots" (excrement).
Lace bug adults have attractive wings that are beautifully sculptured with an intricate pattern that resembles lace. The wings and thorax are flat on top and appear white. The wings extend out over the sides of the black body. Adults are approximately 3/8-inch long. The nymphs are black, spiny and pointed at both ends.
Lace bug damage varies greatly from year to year, presumably in response to variations in natural controls (such as lacewings) and the weather. Severe feeding may cause premature leaf drop, but otherwise healthy trees appear to be unaffected.
Severe damage is usually not noticed until mid to late summer. Treating late in the summer is of little or no benefit to the infested tree. Most damage is done by the nymphs in mid-summer. Spraying will not return green color to the already-damaged leaves.
Though treatment does not help the tree, there may be adequate nuisance created by lace bugs dropping from infested trees to warrant control attempts. Though the lace bugs are harmless to people, pets, structures, and landscape plants there may be a desire to treat to alleviate the annoyance.
ml: isugarden
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