Bugs in Orange and Black, Part II: A spooky southern predator heads north in a warming world – Florida predatory stink bug, Euthyrhynchus floridanus

 

Bedecked in their finest colors of orange and black, Florida predatory stink bugs are now more common in the DMV and other northern states as our world warms.

 

Are utility companies employing Florida predatory stink bugs to do jobs once performed by humans? Image: Craig J. Regelbrugge

Last year was the fifth hottest year in recorded history. This year followed suite with June, July, and August of 2023 being the hottest months ever recorded globally according to the European Union Climate Change Service. Here at home in the United States, if you feel like your town was toastier than normal, you are probably correct as almost 10,000 cities and towns tied or broke daily heat records this year according to the National Weather Service. One of the interesting and ecologically disturbing consequences of climate change is the expansion of the ranges of warm-weather insects to cooler regions where short growing seasons and chilly winter temperatures formerly barred their survival. Last week we met nefarious, collard-crunching harlequin bugs. It should come as no surprise that in addition to plant-eating pests, other insects including beneficial ones have shifted their range. The Florida predatory stink bug is one such beneficial insect that has followed suite and now appears regularly in locations previously thermally off-limits to them.

Florida predatory stink bugs, historically from southern regions, now make regular incursions as far north as New Hampshire and the Dakotas as lethal cold winter temperatures become less frequent. More than a decade ago, in 2012, which was at that time the hottest year on record, Bug of the Week posted an episode noting the unusual discovery of the Florida predatory stink bug sunbathing on the trunk of an elm tree at the University of Maryland. Isolated reports of Florida predatory stink bugs in Maryland date back even earlier than 2012. Last autumn adult Florida predatory stink bugs were seen with regularity in the DMV. Following the second warmest winter ever recorded in the region, it came as no surprise that these fierce predators were back in force in 2023 and numerous reports of this predator surfaced in the DMV.

Last autumn, spooky orange and black Florida predatory stink bugs were spotted on trees and buildings here in the DMV. Were these beneficial denizens of the Deep South able to handle the ‘winter that didn’t happen in 2022/2023’ in this region? Surely looks like it, as developing nymphs and adults were seen throughout our region this summer and autumn. It appears that nymphs of the Florida predatory stink bug have a baffling desire to interpret the dials and readouts on electric utility meters. In a warming world, it looks like they may be here to stay. Video by Michael Raupp and Craig J. Regelbrugge

Color variations in Florida predatory stink bugs range from greenish to black backgrounds bearing orange to reddish spots.  Image: Sarah Zastrow

The Florida predatory stink bug is native to tropical and semi-tropical regions ranging from Peru to the United States. Like its cousin the spined soldier bug we met in a previous episode, the Florida predatory stink bug is a generalist. Using a powerful beak to impale and immobilize its prey, it then sucks nutritious body fluids from the victim to sustain growth, development, and reproduction. In addition to consuming caterpillars and leaf beetles in backyard vegetable gardens, both nymphs and adults of the Florida predatory stink bug put a beat-down on important crop pests including brown marmorated stink bugs and kudzu bugs. As record high temperatures continue to build and growing seasons extend in both spring and fall, keep an eye out for these beautiful beneficial predators that are becoming more common here in the DMV and in locations further north.

Acknowledgements

We thank Craig J. Regelbrugge and Sarah Zastrow for sharing images of Florida predatory stink bugs that inspired this episode. The interesting articles “Florida predatory stink bug (unofficial common name), Euthyrhynchus floridanus (Linnaeus) (Insecta: Hemiptera: Pentatomidae)” by Frank W. Mead and David B. Richman, and “Feeding Responses of Euthyrhynchus floridanus (Heteroptera: Pentatomidae) to Megacopta cribraria (Heteroptera: Plataspidae) with Spodoptera frugiperda and Anticarsia gemmatalis (Lepidoptera: Noctuidae) Larvae as Alternative Prey” by Julio Medal,  Andrew Santa Cruz, and Trevor Smith were consulted for this episode. Records from the Maryland Biodiversity Project helped inform discoveries of this predatory stink bug in the DMV.

Bugs in Orange and Black, Part 1: Nightmare for collards when harlequin bugs arrive - Murgantia histrionica

 

Orange and black harlequin bugs are a nightmare for cole crops.

 

In keeping with the fast-approaching Halloween holiday, the next few weeks we will visit bugs dressed in the Halloween colors of orange and black. Some will be spooky and noxious and others will be helpful and heroic. This week we go spooky and meet the ravager of radishes, killer of kale, and butcher of Brussels sprouts known as the harlequin bug. On a trip to a local community garden, a distraught gardener spoke to me about his withering kale crop. As I strolled around the garden, I spied kale, radishes, and cabbages stunted, discolored, and so severely misshapen that their only remaining use was to grace a compost heap. Upon closer inspection, I discovered legions of orange and black bugs and ranks of minute eggs two and three abreast on leaves. These rascals were harlequin bugs and their spawn. These common pests from the south are kin to several other true bugs we’ve met in previous episodes of Bug of the Week including squash bugs, boxelder bugs, red-shouldered bugs, brown marmorated stink bugs, and wheel bugs. What makes this bug a “true bug” is its gradual metamorphosis including egg, nymph, and adult life stages, sucking mouthparts, and wings partially membranous and partially leathery.

Distinctive barrel shaped eggs colored black and white are an excellent clue that harlequin bugs are about.

Harlequin bugs spend the winter earthbound, hiding in debris left behind from last year’s crops. With the return of spring and the rampant sprouting of wild mustard plants and early season cole crops in gardens, the survivors have a renewed source of food. Cuisine favored by harlequin bugs includes common weeds in the mustard family such as yellow rocket, black mustard, and peppergrass, and several cultivated crops like broccoli, Brussels sprouts, turnip, kale, horseradish, radish, and cabbage. Harlequin bugs also eat plants in the nightshade family such as eggplant. After feeding for several days, females deposit eggs on the surface of the leaf. The eggs hatch into brightly colored nymphs with powerful beaks used to probe tender tissues of the plant and extract nutrients. All of this probing and poking destroys cells and vascular tissues and robs the plant of nutrients needed for growth and development. After five nymphal stages, the bug transforms into an adult that continues to wage war on cabbage and other plants. In southern climes several generations can occur each year, while in the north only one or two generations have time to develop.

These tiny white barrels with black rings are eggs of harlequin bugs. After hatching, small wingless orange and black nymphs search leaves and eventually probe stems and foliage with beaks to remove nutrients. Prior to feeding, winged adults may do a little grooming before settling down to feed with their cronies. After a season of harlequin bug terror, kale and other cole crops may be a mess.

The most striking feature of these bugs is, without question, their remarkable coloration. In previous episodes we learned that bright colors of monarch butterflies and milkweed bugs served as a warning to would-be predators that these insects packed a potent chemical punch. The same is true for harlequin bugs. In a series of clever studies, Drs. Aliabadi, Renwick, and Whitman demonstrated that several species of predatory birds found harlequin bugs distasteful. Harlequin bugs remove noxious compounds called mustard oils from cabbage and other related plants in the mustard family. These noxious chemicals are stored in the body of the harlequin bug to give predators a nasty surprise if they choose to attack. After a few attempts to eat these spicy bugs, birds likely learn to seek more delectable meals elsewhere. The bright coloration provides a reminder of what they should not attempt to eat.

Feeding by wingless harlequin bug nymphs severely damages vegetables like cabbage, kale, broccoli, and other members of the mustard family.

Gardeners have a challenge to keep the buggers at bay and hours can be spent removing adults and nymphs by hand. Another approach to foiling their plans is to plant a trap crop of cabbage or kale very early or very late in the season. In spring as survivors move to the early planted greens, wage war on the concentrated encampment of bugs to reduce the number left to plague crops later in the year. In fall, after most of your vegetables have been harvested, leave just a few cabbages behind to attract any harlequins lingering about. The bugs concentrate on the cabbages and can be annihilated, which reduces the number of bugs moving to the ground to spend the winter. Removing plant debris at the end of the growing season and thermally composting it may further limit the number of tricksters surviving the winter in or near your garden. Harlequin bugs complete many generations in the tropics and Deep South and part of the reason we may be having more problems with these buggers locally resides in our generally warmer winters. A clever recent study found that when winter’s chill dips into the low teens and single digits, mortality of overwintering harlequin bugs increases dramatically. Perhaps true winter will return at the end of 2023 and in the New Year to bring some relief from these orange and black ghouls of the garden.

References

Two great reference books, “Insects of Farm, Garden, and Orchard” by Davidson and Lyon, Wiley Press, and “Garden Insects of North America: The Ultimate Guide to Backyard Bugs” by Cranshaw and Shetlar were used as sources of information for this Bug of the Week. Information on the chemical defenses of harlequin bugs was found in the article “Sequestration of Glucosinolates by Harlequin Bug Murgantia histrionica” by Aliabadi, Renwick, and Whitman, and the interesting article “Supercooling Points of Murgantia histrionica (Hemiptera: Pentatomidae) and Field Mortality in the Mid-Atlantic United States Following Lethal Low Temperatures” by A. S. DiMeglio, A. K. Wallingford, D. C. Weber, T. P. Kuhar, and D. Mullins was also used in preparation of this episode. To learn more about harlequin bugs and their management, please visit the following website: https://extension.umd.edu/resource/harlequin-bug-vegetables

Danger in the wildflowers for bees: Ambush bugs, Phymata spp.

 

Powerful raptorial forelegs enable ambush bugs to snare prey several times larger than themselves. Mottled shades of white and brown allow the hunter to blend with the blossom on which it hides.

 

Sundrenched waning days of summer are often the times when many meadow flowers put on their finest show. Nectar laden blossoms are magnets to dozens of pollinators including bees, wasps, flies, and beetles.  Little do they know that lurking among the inflorescences are deadly masters of disguise. As the name implies, ambush bugs do not make their living by actively chasing and pouncing on prey like six-spotted green tiger beetles or fierce jumping spiders. While speed and power serve some predators well, they are not the only wiles employed by six-legged hunters. Sometimes stealth and deception work just as effectively when it comes to catching dinner. Just ask the praying mantis. Ambush bugs employ an irregular body outline and beautiful patchwork of white and brown or yellow and brown that enables them to blend with colorful blossoms and the light and dark patterns of a flower head.

To find an ambush bug, look for a bee behaving strangely un-bee-like. Hanging motionless upside down beneath a blossom is pretty un-bee-like. A closer examination of the goldenrod flower above the honeybee revealed a rough ambush bug that dropped its prey when disturbed by a giant hand. In another meadow, stealth, camouflage, and an inescapable death-grip enabled an ambush bug to capture a bumble bee several times larger than itself. Strange and beautiful are these crafty hunters.

A perfidious kiss of the ambush bug paralyzes a paper wasp and seals its fate. Liquified tissues of the wasp will be drawn into the digestive tract of the ambush bug through its beak.

These sly killers sit and wait motionless for hours until an unsuspecting victim lands nearby to collect pollen or sip nectar. With a flick of its greatly enlarged raptorial front legs, the ambush bug snares prey that are often several times larger than itself. Ambush bugs are so adept at capturing honeybees that some beekeepers consider them a pest. With the victim in its grasp, the ambush bug inserts its beak into the prey and injects paralytic saliva. Digestive enzymes break down the tissues of the immobilized victim and its liquefied remains are sucked through the beak into the gullet of the ambush bug. Yum! If you want to observe these masters of disguise, find a patch of goldenrod or boneset and look for bumble bees or honey bees dangling motionless beneath flower heads. Carefully examine the unfortunate bee and see if it has been snared by one of these camouflaged assassins.

Acknowledgements

We thank Gordon for discovering the ambush bug that served as an inspiration for this story. An Introduction to the Study of Insects by Borer, De Long, and Triplehorn was used as a reference for this Bug of the Week. To learn more about ambush bugs please visit the following website: http://www.uky.edu/Ag/CritterFiles/casefile/insects/bugs/assassin/assassin.htm#ambush