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During the last week or so numerous reports of home invasions by lady beetles have surfaced with a modicum of confusion about what these creatures are. Misleading headlines like “Ladybug lookalike invading area homes” surfaced. For starters, let’s untangle the moniker thing. The beetles invading homes in many parts of the country during this season belong to a family of beetles called the Coccinellidae. These beetles go by many names – ladybugs, lady beetles, lady bird beetles – and are among the most common beetles in the US. All of these names refer to members of the coccinellid clan, a clade some 5,000 species strong worldwide. The term “ladybug lookalikes” really doesn’t make too much sense as ladybugs and lady beetles are different names for the same group of insects.    

Lady beetles, also known as ladybugs and lady bird beetles, are members of a clan more than 5,000 species strong. Many species are important predators helping to reduce pest populations in gardens, landscapes, and crops. The Multicolored Asian Lady beetle, Harmonia axyridis, is a common home invader in autumn throughout much of North America. It seeks overwintering sites in human-made structures. In natural settings, large aggregations form on rocky outcroppings of mountains where they survive winter’s ire. Harmonia was very abundant in parts of the DMV this year, which caused quite a stir with the public.

The petite invaders recently seen on homes, schools, and office buildings throughout the DMV and in many parts of the country are multicolored Asian lady beetles (a.k.a. Halloween lady beetle) seeking winter refuge. Harmonia axyridis is a prodigious killer of aphids and other nasty pests in our gardens. In one grove of shrubs, I witnessed the annihilation of a booming aphid population. The dazzling lady beetle adults and their alligator-like spawn so completely attacked their prey that I could not find a single living aphid a couple of weeks after Harmonia discovered the aphid patch. Harmonia adults have been reported to consume more than 250 aphids each day, and a single larva may eat more than 1,200 during its development. In addition to eating large numbers of aphids, they devour other pests including adelgids, scales insects, and psyllids.

The alligator-like larva of Harmonia may consume more than 1200 aphids during its development.

Like many predators, they also eat each other. In fact, Harmonia has been implicated in declines of indigenous lady beetle populations on oceanic islands where it has been introduced. As early as 1916, deliberate attempts were made to introduce Harmonia axyridis into the United States from their aboriginal home in Asia, to control aphids. We are not exactly sure how or when this lady beetle established, but by the mid-1980s, it was firmly entrenched in the southern United States. By 1993, it was reported in several Mid-Atlantic States, including Maryland. It is now distributed from Florida to Washington State. Reports of people being “bitten” by ladybugs abound and I confess that I have gotten a small nip from Harmonia every now and then. A recent study discovered that these tiny awesome predators, especially smaller native species of lady beetles, do indeed bite humans and in some cases drink mammalian blood under laboratory conditions. Yikes! Before you duck and cover your jugglers, take solace in the knowledge that Harmonia exhibited no tendency to drink blood.

There are a couple of cautions you might heed as you deal with home-invading lady beetles. When handled or disturbed, lady beetles can release a smelly, bitter secretion that may leave a faint yellow stain on your skin, wall, or curtain. The secretion is a witches’ brew of alkaloids and methoxypyrazines, potent feeding deterrents for would-be predators of lady beetles. There have been reports of pets, particularly dogs, eating lady beetles and becoming ill, so please remind Fido that these are not cicadas and don’t let him eat lady beetles.

Why are there so many lady beetles and what is the fascination with them invading our homes? Remember, these are predators and like many of the other members of their guild, when prey populations increase, populations of predators often follow. With abundant rainfall and lush plant growth providing food for aphids and other juicy prey this spring and summer, it appears that lady beetles had great success finding food, which elevated their survival and reproduction.

Are these lady beetles simply nosey or are we next on the menu now that the aphids are gone? As winter approaches, Harmonia seek protected locations such as crevices and cracks in rocky cliffs and outcroppings to escape the ravages of winter. Throughout the cities and suburbs of the DMV rocky cliffs are scarce, but homes and buildings are plentiful. Like the brown marmorated stink bug we met in previous episodes, this is the time that Harmonia fly to human-made structures and attempt to find refuge. Any cracks around windows, breaks in stone foundations, unscreened vents in the attic, or gaps in facer boards can allow entry into your home. Once inside the beetles settle-in and become dormant for the winter. Many will dehydrate or starve to death indoors, but on warm days in the late winter and early spring survivors may become active and find their way to sunny windows, where they attempt to escape. To prevent lady beetles and other invaders from entering your home, repair screens on your windows and vents, caulk your foundation, seal air conditioners, and eliminate points of entry to your home. Not only will this keep invaders out, but it will also help keep warm air in and reduce your heating costs. If you find the beetles are a problem indoors, carefully sweep or vacuum them up and release them in a protected spot outdoors such as a tool shed or wood pile.

One of the real delights of the season is to visit nearby summits such as the rocky crags of Old Rag Mountain in Virginia or Sugarloaf Mountain in Maryland to witness legions of multicolored Asian ladybeetles gathering on the sunny cliffs for one last bask in the sun before turning in for the winter. But you better hurry. The arrival of the multicolored Asian lady beetle is a sure sign that Old Man Winter is just around the corner.

Acknowledgements

Bug of the Week thanks Kevin Ambrose whose recent account of Harmonia in the Washington Post provided the inspiration for this episode. The interesting study by Sam Ramsey and John Losey entitled “Why is Harmonia axyridis the culprit in coccinellid biting incidents? “, “The chemical ecology of Harmonia axyridis” by John J. Sloggett, Alexandra Magro, François J. Verheggen, Jean-Louis Hemptinne, William D. Hutchison, and Eric W. Riddick, and “Multicolored Asian Lady Beetle” by Joe Boggs and Susan Jones were consulted to prepare this article.

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Autumn is the perfect season to explore Appalachian hiking trails and enjoy spectacular changes in foliage color as deciduous trees prepare to drop their leaves in preparation of winter’s chill. On a recent adventure to Savage River State Forest in Garrett County, Maryland, the westernmost county in the Free State, Fagus grandifolia, American beech, displayed its full glory sporting leaves of russet and gold. As I walked trails lined with these forest monarchs, I was surprised to see the usually unblemished smooth gray beech bark covered with cascades of fluffy white wax. Flocculant wax on leaves or bark is usually a bad sign, as it signals an infestation of some type of noxious sucking insect pest. Yes, this was indeed the case for our friends the American beech, who are in a mortal battle with an invasive insect pest from Europe called beech bark scale and a cabal of invasive fungal pathogens in the genus Neonectria. Together these aggressive pests cause a slowly developing but often lethal disease known as Beech Bark Disease, or BBD.

Beech bark scale belongs to a family of sucking insects called Eriococcidae. This rascal was identified as a pest of European beech trees in the mid-1800’s and was introduced into Nova Scotia in the 1890’s. Since then, it has spread throughout the range of American beech trees in eastern North America. Both adult and juvenile (nymph) beech bark scale insects insert tiny sucking mouthparts into nutritious cells beneath the outer bark of the tree. These stylets pierce and kill underlying cells. As thousands of scales feed, tissues beneath the bark die and bark cracks form. This allows the spores of Neonectria to enter the tree, multiply, and produce eruptive bark cankers, further spreading the fungus. The combined injury caused by thousands of scale insects bursting cells and fungi killing tissues beneath the bark eventually girdle the tree, resulting in a spiraling cycle of death that may take several years to kill their host.

White fluffy wax on the trunk of American beech trees is a good indication of an infestation of beech bark scale. Beneath the wax, tiny nymphs dormant throughout late fall and winter will resume feeding and develop into adults in the warmth of spring and summer next year. As thousands of adults and nymphs feed through the bark, their wounds allow fungal pathogens to enter, multiply, and produce a disease called beech bark disease (BBD). Over the span of several years, BBD can be lethal to infected trees.

In a strange evolutionary twist that we have seen in other insects like beech blight aphids and some scale insects, beech bark scales are parthenogenic, meaning female scale insects skip the business of romance and reproduce without the service of males. These nasty girls rule! Inside their fluffy bundles of wax, nymphs pass the winter months and resume development when spring returns. Wingless adults are present in June and July and new batches of eggs are deposited that will later hatch into mobile nymphs called crawlers. Ok, if adults are wingless how is it that they have spread from Nova Scotia in the 1890’s to western Maryland between 2010 and 2015? Tiny crawlers hatch from eggs and become windborne where they join aerial plankton capable of traveling untold distances on currents of wind. These tiny vagabonds may also crawl onto the feet of birds and be transported from one tree to another as birds migrate and stopover on trees along their route. Some evidence points to human-assisted travel as campers move vehicles around the country with nearly invisibly tiny vagabonds hitching a ride.

Is there any good news for our imperiled beech trees? Yes! Very cold temperatures around 30 degrees below zero Fahrenheit that occur in parts of the range of American beech can be lethal to overwintering scale insects. But in a warming world, this may not be all that helpful. Variation in susceptibility of beech trees to infestations provides hope that some trees carry genes conferring resistance to the scale insect and that resistant cultivars of beech can be bred. Lady beetles, including the twice stabbed lady beetle (gotta love that name), feed on adult and immature beech bark scales, and several insecticides are effective in killing these noxious pests. Insecticides can certainly help for specimen trees in managed landscapes but this tactic is not a solution for the vast stands of beech trees in natural settings. Perhaps Mother Nature has another trick up her sleeve to help quell this invader from overseas. Let’s hope so, but in the meantime take a moment to visit and enjoy American beech trees, remarkable sovereigns of the forest.

Acknowledgements

We thank Dr. Shrewsbury for spotting several beech trees in Savage River State Park. Several enlightening references were used to prepare this episode. They include “Beech bark disease in North America: Over a century of research revisited” by Jonathan A. Calea, Mariann T. Garrison-Johnston, Stephen A. Tealec and John D. Castello, “ Beech Bark Disease” by Esther Kibbe and Enrico Bonello, and “Characterization of mating type genes in heterothallic Neonectria species, with emphasis on N. coccinea, N. ditissima, and N. faginata” by Cameron M. Stauder, Jeff R. Garnas, Eric W. Morrison and Catalina Salgado-Salazar.

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Autumn is a perilous time for many beneficial insects as they strive to collect food reserves to help them survive the approaching winter. In last week’s episode we watched honeybees taking advantage of an unusual source of food, honeydew produced by spotted lanternflies. Premier late season nectar sources for honeybees and many other beneficial insects are native goldenrods, brilliant members of the aster family widely distributed in North America. Rich in nectar and pollen, they help sustain many bees, wasps, and beetles preparing for winter. A few weeks ago, while visiting a favorite patch of goldenrod, I happened across a couple of very cute flies sporting orange and black bodies and feathery hind legs. These belong to a clan of parasitic flies known as tachinids. Some tachinids attack caterpillars, including the nefarious gypsy moth caterpillar, but feather-legged flies have a penchant for members of the “true bug” clan, insects with sucking mouthparts and immature stages called nymphs. Included in this clan are some very bad performers including the brown marmorated stink bug.

Goldenrods are super attractors for many beneficial insects, including feather-legged flies. Flies deposit eggs on many true bugs, like this hapless native leaffooted bug. Eggs hatch and fly larvae bore into the host to develop. With development complete they exit, drop to the ground and pupate in the soil. Adults emerge from the soil to feed, mate, and find new bugs to parasitize. They are known to attack invasive pests, including the nefarious brown marmorated stink bug.

As with many other tachinids, female Tricopoda flies seek hosts on which to deposit their eggs. Stink bugs, squash bugs, leaffooted bugs, and other true bugs are on the hit list. Upon hatching from the egg, tiny fly larvae drill their way through their egg shell and then through the outer skin of their buggy host. Inside their host they develop on the bug’s nutrient rich tissues. Once larval development is complete, maggots bore their way out of the host and drop to the soil below. A pupa forms within the skin of the final stage of the maggot and from this puparium the adult fly emerges ready to find food and a mate. As you might guess, hosts usually succumb to this parasitic invasion.

But how do these smallish flies find their hosts? Insects communicate in a variety of ways using sight, sound, and volatile chemicals to find and join other members of their species. Chemicals used for communication by members of the same species are called pheromones. In a series of fascinating studies, Jeff Aldrich and his colleagues discovered how these parasitic flies locate their victims. Many species of true bugs produce pheromones that serve as assembly calls for purposes of mating or defense. Tachinids use these aggregation pheromones for their own mischievous purpose, to find hosts that will serve as food for their parasitic offspring. While this tale may seem a little dark, the good news here is that native Trichopoda flies have joined other allies, including wheel bugs, garden spiders, robber flies, mantises, and wasps to stymie the shenanigans of invasive pests including the brown marmorated stink bug.      

Acknowledgements

The intriguing references “The biology of Trichopoda pennipes Fab. (Diptera, Tachinidae), a parasite of the common squash bug by Harlan Worthley, “Bug pheromones (Hemiptera, Heteroptera) and tachinid fly host-finding” by Jeff Aldrich, Ashot Khrimian, Aijun Zhang, and Peter Sherer, and “Parasitism of the Invasive Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Pentatomidae), by the Native Parasitoid, Trichopoda pennipes (Diptera: Tachinidae)” by Neelendra K. Joshi, Timothy W. Leslie, and David J. Biddinger were used to prepare this episode.

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Back in September we visited spotted lanternflies as they continued their spread across the eastern United States. In the intervening weeks, several counties in Maryland, West Virginia, New York, New Jersey, and Massachusetts have reported new breeding populations of lanternflies. Recently, we visited infestations in Maryland and Virginia and were astounded not only by the sheer numbers of lanternflies but also by the gushing volumes of honeydew produced by adult lanternflies feeding on the bark of trees. On a bright sunny day in northern Virginia while admiring a throng of these rascally pests in a stand of Ailanthus trees, we were showered by a steady rain of lanternfly honeydew.

Phloem sap is a rich source of carbohydrates for many types of sucking insects, including spotted lanternflies. Large quantities of sap are processed to extract nutrients and the excess fluid is excreted as a liquid waste called honeydew. With hundreds or thousands of lanternflies feeding and expelling honeydew, one can experience rain on a sunny day while standing beneath an infested tree.

While honeydew sometimes refers to a tasty brand of doughnuts or delicious type of melon, in ento-speak honeydew is the sugar-rich liquid waste of sucking insects like aphids, scales, and lanternflies that squirts from their anus. Honeydew is derived from a vascular tissue of plants called phloem which many sucking insects consume. Earlier this year we met another sucking insect, the cicada, that feeds on a different vascular tissue called xylem. Cicadas process great volumes of xylem fluid and excrete copious amounts of watery liquid waste, creating a gentle shower beneath trees on which they congregate and feed. Previously, we reviewed the serious economic threat spotted lanternflies pose to grape growers, orchardists, and the general public, whose lanternfly-infested trees could be fouled by lanternfly honeydew. Economic losses associated with lanternflies in Pennsylvania are currently estimated to exceed more than 50 million dollars annually and are expected to only increase as lanternflies spread.

 As we stood in a gentle honeydew shower, we were chagrined by the diversity and number of stinging insects taking advantage of the sugary bounty provided by lanternflies. Paper wasps, yellowjackets, and hornets greedily collected and often battled over droplets of honeydew. Some even waited near the rear-end of lanternflies, apparently for fresh deliveries. One happy visitor to the honeydew bonanza was our friend the industrious honey bee. As the day warmed and lanternflies amped up honeydew production, growing numbers of honey bees were recruited to this rich sugar source. This may be some good news for our beleaguered bee friends. There is growing concern that honey bees face a dearth of nectar and pollen food sources, especially late in the growing season in temperate regions of our land.  Perhaps honeydew produced by spotted lanternflies can serve as a novel carbohydrate source for our struggling bees. Wouldn’t it be nice if spotted lanternfly, an invasive pest, provided some lemonade and not just lemons in its new home here in the US?   

Honeydew excreted by spotted lanternfly creates a nuisance around infested trees when stinging wasps and bees gather to collect this sweet source of food. But does this honeydew serve as a useful food resource for honey bees?

Acknowledgements

Bug of the Week thanks Sally, Tim, and Mark for providing inspiration for this episode. Special thanks to the great crew of entomologists at Penn State and Virginia Tech working to quell the spotted lanternfly invasion.  The interesting articles “Scientists Examine Potential Economic Impact of Spotted Lanternfly in Pennsylvania” by Amy Duke, and “Native habitat mitigates feast–famine conditions faced by honey bees in an agricultural landscape” by Adam G. Dolezal, Ashley L. St. Clair, Ge Zhang, Amy L. Toth, and Matthew E. O’Neal were consulted in preparation for this episode.

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Last week we visited fall field crickets, whose autumnal home invasions provide cheerful chirps useful in estimating temperatures without a thermometer. Over the past few weeks several inquiries have arrived about a different kind of home invader, spiders. Our home has been graced by smallish wolf spiders dashing across the bedroom floor, cruising the bathroom, slipping in the sink, and audaciously reclining on the bed. What’s up with this?

Wolf spiders are among the most important invertebrate predators providing the ecosystem service of biological control by devouring caterpillars, leaf hoppers, lace bugs, and just about anything else they can sink their fangs into. As generalist predators, they eat a broad range of prey and are vitally important in putting a beat-down on insect pests not only in agricultural ecosystems, but also in residential gardens and landscapes. During this growing season as I tended my flower beds and vegetable gardens, as in previous years, I was amazed and pleased at the abundance of wolf spiders dashing through the mulch and hiding beneath stones. As summer wore on, female wolf spiders were regularly seen toting their dazzling white egg cases slung beneath their abdomen. By late summer and early autumn after these eggs hatched, busy mothers toted scores of tiny spiderlings upon their backs, safe from hungry jaws of other ground-dwelling predators.

Big hairy tarantulas can be spooky, as can the wolf spider with its ghoulish fangs devouring hapless prey. Over the last few weeks wolf spiders have invaded my home. Small spiderlings provide morning surprises on the bathroom floor, in the sink, and sometimes on furniture. But these wolf spiders are not to be feared. They are highly beneficial predators of many pests in our gardens and landscapes. Consider catching them in a cup, glass, or other container and freeing them outside away from the house where they will help eliminates pests in your landscape next growing season.

I often liken these voracious invertebrate predators to large meat-eaters like lions, apex predators sitting high atop food webs. To me, wolf spiders are the clear sign of complex and functional garden food webs. An inquisitive neighbor recently asked “Ok, if there is a smorgasbord of excellent food items outside, why do spiders come inside in autumn?” Great question, because my home probably has a bug or two but nothing compared to my garden. A possible explanation lies here. Our resident spider expert explained that as autumn wanes, the bounty of spider prey declines dramatically outdoors as insects and other invertebrates hide in hibernal redoubts or migrate to warmer latitudes. With declining sources of food, these wandering hunters are forced to travel farther to find a meal. Their search may bring them to homes and other structures where faulty door-sweeps, caulking, or weather-stripping allow them to enter and deliver spooky morning surprises.

Spider invasions might be terror for arachnophobes, but for bug geeks close encounters of an arachnid kind provide an opportunity to hone one’s spider catching skills. Here’s what we do. Using a drinking glass or, better yet, a dedicated green plastic spider-catching cup, we chase down and corral these rascals. Often, we simply use a hand to usher the spider into the cup, but if touching spiders is not your thing, a tissue or piece of paper may help you guide them into their holding cell. Once captured and admired, they are released outdoors to fulfill their spidery roles of hunting pests in the garden. Of course, closing gaps with caulk and weather-stripping and replacing faulty door sweeps will not only help exclude spiders, but with Old Man Winter just around the corner, these easy home improvements will also help keep those heating bills down.

Happy Halloween from Bug of the Week!  

Acknowledgements

We thank spider-loving Ashley and the inquisitive crew of the Weather Channel for providing inspiration for this episode. Dr. Jeff Shultz provided interesting insights into these home invasions, and the fascinating review “Spiders as biological control agents” by Susan Reichert and Tim Lockley provided background information.

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In previous episodes we visited rather unsavory home invaders like stink bugs and camel crickets. This week let’s meet a most entertaining and downright amusing visitor, the fall field cricket. Several weeks ago, chirps from the basement heralded the annual invasion of field crickets to my home. Last week at 4:35 am I was awakened by the loud earnest chirping of a field cricket somewhere in the basement. With my sleep seriously disturbed and my cell-phone on the nightstand, I seized the opportunity to see how well chirps of this diminutive troubadour tracked ambient temperature. Here’s how it works. As you know, insects are cold blooded. Their body temperature is more or less the same as the environment that surrounds them unless the insect is basking in the sun or using muscles to elevate its temperature like the dobsonfly we met in a previous episode. Many years ago, a noted entomologist, Richard Alexander, demonstrated a simple relationship between ambient temperature and the how often a cricket chirped. Simply count the number of chirps in 15 seconds, add 37, and you will approximate the ambient temperature in degrees Fahrenheit. With sleep impossible, cell phone in hand, stopwatch enabled, I sampled my cricket’s chirps several times at 15 second intervals over the next few minutes. The average number of chirps per 15 seconds was 40. So, this little guy (only males chirp) reported my household temperature to be 40 + 37, or roughly 77 degrees. A quick check of the household digital thermostat revealed a temperature of 74 degrees. So, the cricket’s estimate was but a few chirps away from being spot on.  

This little field cricket demonstrates his skill at helping humans estimate ambient temperatures. Counting the number of chirps in 15 seconds and adding 37 provides an estimate of ambient temperature. Let’s see how well this works.

Although some might think so, helping humans figure out ambient temperature is unlikely the reason why crickets chirp. A few years ago, I tracked two male crickets, one of which was missing a hind leg, and a rather portly female. Never one to stand in the way of romance, I captured the trio and placed them in a small terrarium. Within moments the smaller male, the five-legged fellow named Pete, challenged his cohabitant, Bud, to a duel that resulted in boisterous chirping, snapping of jaws, and grappling with forelegs. The more aggressive Bud soon vanquished his challenger and Pete retreated to a quiet corner of the terrarium. Crickets battle for food and mates and chirping is a part of this. For centuries Chinese gamblers have wagered high stakes on the outcome of cricket fights.  An interesting trick used by the cricket handlers to resuscitate losers of bouts is to shake the defeated warriors and toss them in the air several times. This dramatically reduces the recovery time and allows the small combatants to return to the arena in minutes rather than the regular convalescent period of hours or days. A study published in Nature scientific journal confirmed the success of this therapy in helping defeated crickets regain their fighting spirit. Rather than interrupt Nature’s course, I allowed Pete to sulk in the corner. Shortly after his victory, Bud initiated a series of soft chirps and his efforts were soon rewarded by a visit from the robust female, Wendy.  

What useful information is carried in the male cricket’s song other than the typical male plea for female attention? A fascinating study by two Finnish scientists of the Mediterranean field cricket, Gryllus bimaculatus, found a link between the male cricket’s song and his immune response. Troubadours with a highly attractive song also had superior immune systems. If the ability to ward off diseases due to superior immune function is passed along to progeny, then females that choose a mate with an enhanced immune system may ensure better survival of their offspring. By demonstrating his superior immune system with a song, the male cricket may win the lady.  

One last thought about the cricket and his song relates to Old Man Winter, who is just around the corner. Of course, once winter’s chill arrives in a few weeks and temperatures plummet, crickets will not be chirping at all. Rather than depending on crickets to let you know how cold it is outside, time will be better spent inside pondering crickets and their songs over a mug of steaming hot chocolate. 

Acknowledgements

The following articles were used in preparation for this Bug of the Week: ‘Courtship song and immune function in the field cricket Gryllus bimaculatus” by Markus Rantala and Raine Kortet, “Aggressiveness recovers much faster in male crickets forced to fly after a defeat” by Hans A. Hofmann and Paul A. Stevenson, and “Seasonal and daily chirping cycles in the northern spring and fall field crickets Gryllus veletis and Gryllus pennsylvanicus” by Richard Alexander and Gerald Meral.

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American sycamore is a magnificent native tree often found growing along streams and rivers. Although it thrives in rich, moist soils, its ability to survive stressful environmental conditions such as poor soils, drought, heat, and pollution has earned sycamore a valued place in cities and residential landscapes worldwide. Here in the DMV by the middle of summer and reliably by the month of October, some sycamores just look sick. Their leaves have turned from verdant green to anemic yellow. This is not just the work of Mother Nature signaling the tree to prepare for winter. Since late spring, many sycamores have had the life sucked out of them by thousands of tiny sap-sucking insects called sycamore lace bugs. We met relatives of the sycamore lace bug in a previous episode of Bug of the Week called “And may all your azaleas be white.”

One leafy subject I examined this week had more than 200 lace bug eggs, nymphs, and adults on the undersides of several of its leaves. Beautiful but pernicious is the adult lace bug. Delicate outermost wings with numerous lacey veins give this bug its common name. And these wings are not just adornment. They can be tilted like a shield to ward off attacks by would-be predators like lacewing larvae or ladybugs. As autumn ends, adult lace bugs find protected places beneath bark or debris on the ground to spend the winter. In spring shortly after new leaves are formed, they return to the foliage and attach small black barrel-shaped eggs onto the leaf’s surface. The highly fecund female can lay more than 200 eggs during the course of her lifetime. Tiny black nymphs festooned with rows of spines hatch from these eggs. Like their parents, lace bug nymphs have a beak used to rupture cells and withdraw nutritious liquid contents. The combined feeding of nymphs and adults results in many tiny white stipples visible on the upper leaf surface. The lower surface of the leaf is a mess of nymphs and adults, shed skins, eggs inserted into leaves, and dark fecal spots – the spoils of the ongoing feast. As numbers of lace bugs grow and successive generations feed on leaves, stipples increase and sometimes coalesce in a way that makes the entire leaf appear yellow or bronze.

White stipples on the upper leaf surface of sycamores may reveal adult sycamore lace bugs on the lower surface. Look for barrel-shaped eggs, spiny nymphs, shed skins, beautiful adults, and nasty tar-like fecal deposits left behind by lace bugs as they feed. Dense infestations may accelerate discoloration and early abscission of sycamore leaves.

Lace bug development is temperature dependent and, as the world warms and our cities grow hotter, lace bugs may be able to complete more generations each year. If lace bugs and their damage are too great, the sycamore may simply drop its leaves and bring a premature end to the lace bug’s shenanigans. Other factors such as lack of nutrients or water may also cause sycamore leaves to turn yellow and fall, but one sure way to rule lace bugs out or in is to turn the leaves over and inspect them for the telltale signs of a lace bug infestation – lace bugs at all life stages, shed skins, and their fecal deposits. We often lament the fact that so many pests of our forests and gardens, like emerald ash borer, brown marmorated stink bug, and spotted lanternfly, arrived in North America from foreign lands. In the game of global economic tit for tat, our native sycamore lace bug is another example of a pest we have shared with other neighbors around the world, including more than three dozen nations in North America, Europe, Asia, and Oceana, where sycamores are widely planted and now regularly attacked by this insect. 

Acknowledgements

We thank Veronica Robinson and John Neal for providing the inspiration for this episode. The interesting references “Corythucha ciliata (sycamore lace bug)” at the CABI website https://www.cabi.org/isc/datasheet/16264#tosummaryOfInvasiveness, and “Managing Insects and Mites on Woody Plants: an IPM Approach” by John Davidson and Michael Raupp, were used as references for this episode.

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