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In previous years we visited eastern tent caterpillars when they appeared on native black cherry trees in the last week of March or first week of April. Guess what; following the warmest January and February in the last 150 years in Washington, DC, these impatient tent makers began to hatch last week just up the road from DC in nearby College Park, Maryland. Under “normal” climatic conditions, this would pose no real concern for caterpillars, but this year trouble may be brewing. While the hatch of caterpillars is underway, some black cherry trees which normally provide leaves to sustain eastern tent caterpillars, have yet to heed Mother Nature’s wake-up call. Fascinating studies of eastern tent caterpillars in Washington, DC, demonstrated that warm winter temperatures induced earlier hatching of caterpillars, which resulted in reduced survival of caterpillars due to starvation – suicidal emergence.

Watch as an eastern tent caterpillar emerges from its egg. It will join dozens of siblings that have already hatched on the surface of an egg mass deposited by its mother last year on a black cherry tree. But will this early arrival spell doom by starvation for the caterpillars on a tree yet to produce tender buds and leaves to sustain caterpillar growth? Scientists fear that climate change may result in harmful seasonal mismatches between herbivores, pollinators, and plants on which they depend.

Scientists found that early starvation put a serious beat-down on survival of hatchlings. These studies also demonstrated that eastern tent caterpillars from different regions vary in their ability to survive periods of starvation. Populations of resilient eastern tent caterpillars from Georgia were able to survive starvation for periods that were 30 % longer than tent caterpillars from DC. As climate change continues to create havoc for long-evolved relationships between plants and insects, and with chilly rains and freezing nights forecast over the next two weeks, will wild cherries wait for warmer temperatures to break bud and expand their leaves? And if foliation is delayed, what will it mean for our cherry-loving tent caterpillars? Only time will tell.

Acknowledgements

The enlightening article, “Warming affects hatching time and early season survival of eastern tent caterpillars” by Mariana Abarca and John T. Lill provided inspiration and insights for this episode. To learn a bit more about eastern tent caterpillars, how to remove them and how to enjoy them, please visit this episode of Bug of the Week – Food for caterpillars, food for birds: Cherry trees and Eastern tent caterpillars, Malacosoma americanum.

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In a previous episode we learned of trouble in the greenhouse brought on by tiny thrips wreaking havoc on white swamp lilies. This week we return to the greenhouse where yet another sucking insect is pestering our growers. Mealybugs are a clan of mostly tropical and semitropical sucking insects that often outbreak on plants in greenhouses, interiorscapes, and homes wherever indoor plants are grown. One common offender is the citrus mealybug. Originally native to Asia, the citrus mealybug has been recorded in the United States since 1879 and is now found in Asia, North, South, and Central America, Europe, and Oceana. They are major pests of fruits such as citrus, grapefruit, and bananas but are known to dine on plants from more than 60 plant families. Yikes!

Like aphids, soft scales, bark scales, whiteflies, and lanternflies we met in previous episodes, mealybugs insert sucking mouthparts into phloem vessels and imbibe sap. This robs plants of vital nutrients which results in yellow foliage, distorted leaves and buds, premature leaf drop, and plant death. As with other phloem feeders, all that sucking and processing of liquid food results in the excretion of vast amounts of sweet sticky honeydew. Recall that honeydew is the substrate for the growth of unsightly sooty mold which disfigures foliage, blossoms, and fruit. This sugar-rich liquid attracts ants and stinging insects. Cold winter temperatures prevent citrus mealybugs from surviving in most states here in the US, but in the warmth of Florida and California they complete several generations annually and indoors they can survive and reproduce year-round. With females able to produce up to 600 eggs, it’s easy to see how populations can explode seemingly overnight.  Female mealybugs are flightless, so infestations often begin when previously infested plants arrive in a greenhouse or home. Tiny mealybug nymphs ride air currents to move from one plant to another.

Watch as an adult mealybug destroyer moves across an infested leaf and gobbles up small mealybug nymphs along the way. On another leaf, the wax covered larva of a mealybug destroyer searches for prey and when it finds one, it settles in for a juicy mealybug meal topped off with a little wax.

But all is not lost for our grower and the greenhouse plants under his care. Citrus mealybug has a powerful foe, the mealybug destroyer which has been released in the greenhouse. Native to Australia, this small lady beetle was imported to southern California by pioneering entomologist Albert Koebele in the late 1800’s to help control citrus mealybug, which threatened California’s burgeoning citrus industry.  This classical biological control success story has been repeated in other countries around the globe and the mealybug destroyer is now found the Americas, Europe, Africa, and Oceana. While adults certainly have a lady beetle mien, their youngsters don’t appear very beetle-like at all. Immature stages of this tiny terror are cloaked in white wax and appear much more like mealybugs than beetle larvae. Scientists believe this may be a clever ruse to fool potential predators such as ants that protect honeydew-producing insects like mealybugs. By resembling their prey, larval mealybug destroyers may escape the fierce jaws of ants defending mealybugs. Both adults and larvae of the destroyer have a keen appetite not only for citrus scale but for other pestiferous scale insects as well. They can be purchased commercially and are part of the natural enemy arsenal used to put a beat-down on mealybugs around the world.

Acknowledgements  

We thank Nancy Harding and Sam Bahr for sharing their mealybugs and mealybug destroyers which inspired this episode. To learn more about mealybugs and the mealybug destroyer please click on links at these uber-informative websites at the University of California IPM websites:

https://ipm.ucanr.edu/PMG/PESTNOTES/pn74174.html 

https://ipm.ucanr.edu/natural-enemies/mealybug-destroyer/

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Digging through the mailbag, I came across an inquiry from a budding nine-year-old naturalist who discovered an unusually large beetle larva that had expired on her driveway. The grub was none other than the back-walking larva of a turf pest known as the green June beetle. Like other larvae of the scarab beetle clan, green June beetle grubs use three pairs of legs on their thorax for short distance feeding sorties. But when it’s time to get up and really go, they move out of the soil and use a very bizarre form of locomotion – “walking” on their back. These wiggly critters have a series of stout hairs on the upper surface of their back. To move quickly above ground, the grub rolls on its back and with peristaltic motions it wriggles across the surface of the earth or a driveway. Dorsal hairs contact the substrate and provide ample traction for surprisingly rapid movement. The unfortunate star of this week’s episode likely emerged from turfgrass adjacent to an expansive driveway on an unusually warm December day. As temperatures plummeted from afternoon highs near sixty to post sunset lows in the thirties, the back-walker apparently was stranded and unable to regain the relative warmth of the soil. When our third-grader discovered the grub the following evening, with temperatures still below freezing, the larva had suffered the same ill fate as the Scott party in Antarctica. 

Using a backstroke even Michael Phelps would admire, a green June beetle larva races across my patio.

Most green June beetle grubs choose a slightly different path to follow. After feeding for several months near the surface of the earth, grubs, which may be an inch and a half long, burrow deeper underground to escape winter’s bitter cold. In spring as temperatures warm, larvae return to the upper stratum of the soil to resume feeding and complete development. Most of the damage caused by grubs results as they move to the surface of the soil to feed. Their burrows can be the diameter of your thumb and small mounds of soil often surround the burrows. The soil disruption caused by burrowing beetles creates problems on golf courses and in lawns. Soils with organic mulches and farm fields that receive applications of manure are highly attractive to the egg-laying females and may be loaded with grubs. 

On hot summer mornings, adult green June beetles zoom over the surface of lawns as they search for mates and sites to deposit eggs. While many beetles spread their hard outer wings to fly, green June beetles simply lift their hardened outer wings and extend membranous hind wings used for flight. The flight patterns and buzzing sounds of green June beetle adults are strongly reminiscent of large bumble bees. Perhaps, these behaviors are a clever way to ward off would-be predators that learned not to mess with large buzzing, stinging insects. Once a female locates a favorable spot, she burrows several inches into the earth, makes a large sticky ball of soil and proteinaceous goop (technical term), and deposits eggs in it. Eggs hatch in a few days into small C-shaped white grubs. During the day, white grubs rest in a burrow underground but at night they move to the surface of the earth to eat decaying organic matter. With some regularity in late summer and autumn, these rather large white grubs wind up on my patio or in the carport and perform their strange back-walking routine. 

Watch as green June beetles take flight, first at full speed and then slowed by 95%. See the unusual position of the wings where hard outer wings remain closed and membranous hind wings are extended outward and used for flight.

Unlike their more destructive relatives, Japanese beetles, Asiatic garden beetles, and Oriental beetles, green June beetles are not serious pests of roses, lindens, or other landscape plants. Their primary foods are thin-skinned fruits such as berries and grapes. I have also observed several adults congregating on a wounded tree to slurp fermenting exudates. Fresh fruit and fermenting beverages sound just fine on a warm summer’s day. Maybe these green June beetles are just a bit smarter than we think. 

Acknowledgements 

We thank nature-lover Eloise for sharing her beetle grub that was the inspiration for this episode. Much of the information for this Bug of the Week came from Daniel Potter’s excellent reference book “Destructive Turfgrass Pests” and the interesting article “Mimicry of Hymenoptera by Beetles with Unconventional Flight” by R.E. Silberglied and T. Eisner.

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This week we dip into the mailbag to see how ill-fated wasps can help create fascinating pottery when they select poor locations to build their nurseries. While performing an annual tune-up of a woodburning stove, an inquisitive homeowner discovered a strange foreign object in the bowels of the firebox. His first thought was that this might be a piece of cast iron slag or creosote accretion. Upon closer examination, he astutely identified the mass as a mud dauber nest that had been “fired” by the heat of his stove. With some remorse, he reflected on how many trips the mother wasp must have made up and down the fifteen-foot stovepipe to construct the nest, only to have her youngsters roasted alive in a stove. Well, to learn a little bit more about industrious mud daubers, let’s revisit an episode from 2017 about one of my favorite wasps, the black and yellow mud dauber.

“On a steamy day in Maryland, nothing beats a trip to one of our mighty rivers, the Potomac or Shenandoah. After a fierce hike on a scorching day, I stopped by the Shenandoah at Harper’s Ferry to cool my hot feet. Along the riverbank dozens of mud daubers discovered what must have been the perfect formulation of clay, minerals, and water to construct pottery homes for their young. In an amazing display of harmonized movements, mouthparts and legs of mud daubers formed spheres of glistening mud and airlifted mud balls to nearby human-made structures. Corners of window frames and doorjambs were perfect locations out of the rain to build pottery homes for their young. Nest construction by Sceliphron caementarium centers on creating a series of hollow mud chambers, provisioning each chamber with food, depositing an egg in each chamber, and sealing the mud tubes with a cap of mud to keep out weather, but more critically parasitoids and predators intent on making a meal of mud dauber larvae.

Watch as mud daubers use clever jaws and legs to shape mud into perfect balls ready to be airlifted to the nest construction site.

Just what are the provisions for babes of black and yellow mud daubers? Spiders, lots of them. Individual cells of mud daubers may contain as many as 25 spiders to serve as food for a single wasp larvae. Several species of web spinning and hunting spiders have been discovered in nests of mud daubers. One might think that spiders are pretty risky food for baby wasps but mother has a way to disarm these fanged prey. Female mud daubers deliver a venomous paralytic sting to the nerve center of the spider, rendering it immobile and harmless. These spiders are the ‘undead’. Sealed in clay coffins, spiders will be consumed alive one-by-one by the developing wasp larva. When the last spidery zombie in the chamber is consumed, the wasp larva pupates and later emerges as an adult ready to find a mate, build mud nests, and capture spiders for young of her own. Unlike the venom of hornets, yellowjackets or honey bees that is meant to inflict pain on vertebrates intent on robbing nests or hives, the venom of mud daubers is designed to paralyze prey and the sting of these docile wasps is reported to be mild by comparison, much like the sting of solitary bees we met in a previous episode.

The primary concern raised by these beautiful spider hunters is the aesthetic disfigurement of buildings where clay nests stuck on walls, doorjambs, eaves, and window frames can be very abundant. In an interesting twist to this mud dauber story, workers cleaning up a nuclear waste facility apparently found wasps gathering radioactive soil to build their nests and many of their creations were “fairly highly contaminated” with radioactive isotopes. Just imagine giant mutated wasps glowing in the dark, capturing small pets instead of spiders to provision their nests – sounds like reasonable grist for another B grade sci-fi movie about insects!” While the firing of a mud dauber nest might seem somewhat tragic, there is a reasonable chance that this nest was occupied in years past and that the larval chambers were empty. Mud daubers do not reuse former nests so maybe no carnage was involved. As our human friend concluded, he may simply be the proud owner of a “goofy conversation piece.”

Acknowledgements

Thanks to Andy Smith for sharing his story and images that inspired this episode. Paula Shrewsbury provided a great photograph of the black and yellow mud dauber. The wonderful Featured Creature Sheet “Common name: black and yellow mud dauber, scientific name: Sceliphron caementarium (Drury, 1773) (Insecta: Hymenoptera: Sphecidae)” by Erin Powell and Lisa Taylor, and “Radioactive wasp nests at Hanford reservation” by the Associated Press were used to prepare this story.

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Got a call a few weeks ago about white swamp lilies feeling the blues from a greenhouse grower. White swamp lilies, Crinum powellii album, are a spectacular member of the amaryllis clan known for their extremely fragrant white blossoms, which give them their common name.  While it can be planted outdoors in plant hardiness zones 6 – 11, at the northern edge of its range freezing temperatures cause dieback of above ground foliage. The white swamp lilies in question here also suffered above ground dieback of foliage, but resided in a campus greenhouse where temperatures were a balmy 65 degrees Fahrenheit or so. Ruling out the possibility of cold intolerance, a justifiably frustrated grower wondered why the sickly yellow and brown leaf color and decline of the lilies was happening. At first glance, silvery streaks and discolored patches of morbid leaf tissue necessitated a closer look. A peek through the 20X hand lens revealed a horde of tiny thrips cavorting, feasting, and despoiling the plant. A tentative identification of the culprit suggested this was the banded greenhouse thrips, a pest found outdoors in pantropical regions and in greenhouses around the world where it dines on a wide variety of vegetables, fruits, and ornamental plants, including lilies.

Thrips are strange little insects with an unusual name that is both singular and plural. Ten of these creatures are thrips, but a single individual is also a thrips. In addition to a strange name, they have equally strange and formidable mouthparts. A dagger like jaw punctures epidermal and parenchyma cells of the leaf and another set of mouthparts slurp up nutritious cell contents. Thrips feeding causes discolored areas of leaf tissue and sometimes silver streaks on the surface of a leaf. The immature stages of thrips, called larvae, are translucent and often yellow or whitish in color. They cannot fly and molt several times before transforming into winged adults capable of flight. Depending on the species, adults can be yellow to dark brown in color, as is the case with the fiends on our swamp lilies. Their tiny wings, lined with featherlike hairs, are the source of their Latin name, Thysanoptera, which means “feather wing”. 

This white swamp lily is really in the hurt locker with leaves yellowing and crumpling in a death wilt. Zooming in on a leaf, we see silver streaking and a row of tiny black adult thrips dining near a leaf vein. Herds of larval thrips, many wearing a black fecal droplet on their rear end, feed on leaf tissue. Watch the digestive tract of a thrips larva pulse and quiver as it imbibes liquids from a leaf. Nearby, an adult thrips seems more intent on grooming its antennae rather than dining on a leaf.

Female thrips can lay scores of eggs. Indoors where plants are warm and dry during winter months, thrips may complete multiple generations over the course of several weeks. In addition to damage caused as they feed, thrips leave behind little gifts in the form of black fecal deposits. These small treasures litter the surface of the leaf and collect on surfaces below the plant. A vigorous washing with a spray of water may dislodge some of the thrips and provide a modicum of relief. However, many species embed their eggs in the leaf tissue and these are unlikely to be dislodged by a spray. Many insecticides are available to kill thrips. One active ingredient that can be purchased by homeowners and professionals alike is spinosad. Derived from the soil inhabiting bacterium, Saccharopolyspora spinosa, spinosad is approved for use not only on greenhouse plants but also in the production of certified organic vegetables.

Ah, but a more natural and perhaps more entertaining way to manage them is to release hungry predators with a taste for thrips. Greenhouse growers manage these rascals by releasing predatory mites or minute pirate bugs that attack and eat thrips in a strategy called biological control. Another biological control tactic that has proven effective is to treat thrips with entomopathogenic (insect killing) nematodes. These tiny roundworms can be purchased and sprayed on the plant and underlying soil to kill developing thrips. The nematodes invade the body of the thrips and release a lethal bacterium. However, when plants are heavily infested with thrips, sometimes the best strategy is to say goodbye to the old ones, and “gift” yourself a new one.   

Acknowledgements

We thank Sam Bahr for discovering the thrips featured in this episode and Juang Chong, Dan Gilrein, Felipe Soto-Adames, Matt Bertone, Mark Hoddle, Frank Hale, and Stanton Gill for helping with the identity of this rascal. The fact-filled fact sheet by Ronald F.L. Mau and Jayma L. Martin was used to prepare this story.

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Discover the Signs of Mice in the Attic of Your Home and How to Prevent Infestations Once and for All

Are you dealing with a mice infestation in your attic? Catseye Pest Control helps homeowners remove mice from their homes, clean up the mess, and prevent future rodent infestations. 

Mice and other rodents invade more than 20 million American homes ever year, typically in search of warmth, shelter, and food. These fast-moving, destructive critters can squeeze through openings as tiny as a dime, making it easy for them to enter and exit homes.

They eat 15 to 20 times a day, can jump and climb with ease, making it easy for them to get into all kinds of trouble. Mice can invade every part of your home, but one of their favorite places to set up house is the attic.

Once inside, mice can cause significant destruction.

The Damage Mice Can Do to Attics

Mice may be tiny, but they create huge amounts of damage relatively quickly. In fact, mice and other rodents create millions of dollars of damageto homes and businesses every year.

Some of the destruction caused by these pests in attics includes torn and damaged insulation as they gnaw through it and make their nests inside. Insulation may also become contaminated with feces and urine.

Constant gnawing can also destroy parts of the structure in addition to valuables stored in the attic. Worse, mice are known to chew on just about anything — even electrical wires. Left unchecked, small nibbles can lead toelectrical shorts and possible fires.

These rodents also reproduce quickly. A single female can have a dozen babies every three weeks, turning a small problem into a huge infestation.

Mice are also known to make their way throughout homes, rather than staying in the attic. They can quickly and easily move into the walls and the crawlspace, widening the scope of their destruction.

Mice Rarely Stay in the Attic

Left undisturbed, mice will feel safe to move in permanently and roam throughout the structure.

In addition to building nests to have their young, they will inevitably spread out. They may move into walls, crawlspaces, basements, and other rooms — anywhere dark, quiet, and out of the way.

In the process, they will spread germs and possibly diseases while creating damage throughout more areas of the home.

Signs You Have a Mouse (or Mice) in the Attic

Like all rodents and other wildlife nuisances, mice in the attic leave telltale signs of their presence. If you suspect there is a mouse (or likely, mice) in your home, it’s critical to call for professional assistance. Although there are do-it-yourself efforts available, not properly handling the situation can lead to a bigger infestation if all of the critters are not removed.

 It can also lead to the spread of virus-containing particles — like Hantavirus, which can be spread through urine, droppings, or saliva-covered matter that is improperly moved or disposed of.

Some of the main signs of mice in the attic include odd noises, such as scratching or scampering overhead or behind walls. Mice tend to be more active at night, so keep an ear out in the evening, overnight, and early morning.

Look for rub and gnaw markson wood panels, furniture, and flooring. Nests made of insulation, paper, or cloth are common in attics, crawlspaces, walls, and basements infested with mice.Droppings will often be found near nests or areas with food.

Additionally, you might start smelling odors, including musky smells or urine.

Removal and Treatment

Knowing what to look for is half the battle. Developing a plan to remove invaders and keep them out is equally essential.

Catseye has a comprehensive mouse control program to eliminate the infestation. It also includes steps to clean and disinfect the mess they leave behind, and it offers permanent solutions to prevent future issues.

The faster you respond, the better. Because mice reproduce so quickly and can nest in out of the way areas, total elimination can be challenging. Working with experts in the field can help you regain control quickly.

Exclusion Systems Offer a Permanent Solution

To prevent mice from returning to the attic, and other parts of the home, it’s essential to identify how they are entering and seal off those entry points.

Catseye’s expert technicians can help with the process and recommend a permanent barrier. Cat-Guard Exclusion Systems work to provide complete, chemical-free defense for various zones of the home. Each all-natural, rigid barrier shields the home, guaranteeing permanent prevention for mice and nuisance wildlife.

• Upper Cat-Guard protects everything from the top of the first-floor windows to the peak of the roof.
• Lower Cat-Guard shields the home from the first-floor windows to ground level.
• Trench-Guard seals off low-clearance and subterranean areas like basements, decks, crawlspaces, and sheds.

Trust Catseye with Your Mouse Removal, Treatment, and Prevention Needs

Mice (and their droppings) can transmit serious diseases. Additionally, these small but persistent pests can do significant damage that won’t likely remain contained to the attic. Eventually, they will spread out to crawlspaces and other areas of the home.

Catseye has decades of experience and a commitment to not only meet but exceed your expectations, starting with our free, detailed inspection. Contact us today to schedule an appointment or to learn more.

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On a warm early winter day, while tidying up a screened porch, I happened upon a lovely cellar spider taking a stroll with its shadow along piece of misplaced lumber. Somehow, that old classic by Al Jolson, Billy Rose, and Dave Dreyer got stuck in my mind and wound up in the title of this episode, but here’s the rest of the story. Just beneath a nearby workbench rested a motley collection of exsanguinated arthropods including a field cricket, ground beetle, weevil, small millipede, and tiny wasp tangled in silk. Telltale white droplets of excrement beneath a loose silken web marked this as the graveyard of victims of a cellar spider. A few years ago, in late autumn with the holiday season fast approaching and family and friends soon to visit, the Bug Guy received orders to prepare the spare bedroom in the basement for overnight guests. Part of the assignment was to inspect windows and remove any arthropods living or dead that might terrorize visitors who do not share affection for animals lacking fur and possessing more than four legs. Near the corner of one dimly lit window, I discovered a diverse collection of tiny insect carcasses and didn’t have to look far to see a gangly and beautiful cellar spider hiding in the upper corner of the window.

With the late autumn sunlight at just the right angle, a cellar spider takes a stroll with its shadow along a piece of lumber near my workbench. High on an interior wall with her egg case snugly tucked beneath her body, a mother cellar spider rests. While she spends most of her time building webs, catching prey, or just chilling out, watch what happens when she is disturbed by a bug geek. Rock on spider, rock on! Rocking the web is believed to be an anti-predator behavior in cellar spiders and many of their kin.

Cellar spiders are found throughout much of the world in temperate and tropical regions. Millions of years ago cellars were noticeably absent from the planet but caves and dank tree hollows were aplenty and cellar spiders found these habitats perfect for building their loose webs for snaring prey. In the Land Down Under and in some other parts of the world, cellar spiders go by the name of daddy-long-legs, a moniker associated with another arachnid, opilionids, which we met in a previous episode.  I have handled cellar spiders and never been bitten and if this rare event did happen, the spider’s bite is reported to be harmless to humans. However, the cellar spider can bring down formidable spiders including Australian redbacks, kin to our black widow.

Mating is a curious affair in many spiders including Pholcus. Male cellar spiders deposit a droplet of sperm onto a small web, and then gather the droplet and store it in an appendage called the pedipalp. He then deposits the sperm into a cleft in the female’s abdomen where the sperm will be stored until the females uses the little wigglers to fertilize her eggs. Female cellar spiders are not necessarily “you and only you” kinds of gals and will often mate with more than one fella. In the spider mating game, it turns out that sperm from the last mating are the ones most likely to fertilize eggs. So, to ensure that he will be the proud father of spiderlings, the male removes sperm placed by his betrothed’s last suitor before he makes his deposit. What a guy. After all this drama, the female lays eggs and encases them in a thin cloak of silk. The egg bundle is toted about in their mother’s jaws to reduce the likelihood of being discovered and eaten by tiny predators. Like wolf spiders we met in a previous episode, tiny spiderlings also hitch a ride with mom for a short period of time after hatching.  If some winter cleaning is on your to-do list, before you attack those corners in the basement with vacuum or duster, take a moment to observe and maybe even enjoy these helpful predators. Or not.    

Acknowledgements

Bug of the Week thanks Dr. Jeffery Shultz for identifying the spider featured in this episode, Dr. Nancy Breisch, and the Bartley Raupp’s for providing inspiration and guidance for spider stories. Great references used to prepare this episode include “Daddy-long-legs Spider” by Dr. Mike Gray, and “Pholcus phalangioides” by Anna Ferrick.

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In a previous episode we met strange gall-forming psyllids making their homes on leaves of the sacred ʻŌhiʻa tree, Metrosideros polymorpha. Once again, we escape the chilly confines of the DMV and return to the big island of Hawai’i to visit another intriguing family of insects, picture-winged flies, Drosophilidae. The Hawaiian archipelago formed and continues to grow as tectonic plates beneath the Pacific Ocean pass over a volcanic “hot spot.” This movement of the earth’s crust spawns enormous land masses that eventually emerge from the sea, the islands of Hawaii. For millions of years, this ongoing process has created new land, pristine habitat awaiting the arrival of plants and animals in what has been called an “evolutionary laboratory.” At some point in time eons ago, ancestral picture-winged flies, voyagers by an unknown conveyance, arrived on the islands and initiated a process of evolutionary adaptation exploiting the bountiful resources and diverse climatic regimes found in this tropical paradise. This unending process has resulted in almost 700 named species of drosophilids inhabiting the Hawaiian Islands, with another 300 or more yet to be described.

At the Hawai’i Tropical Bioreserve and Garden just north of Hilo, strange cannonball trees produce fragrant flowers along the length of their trunk. After visitations by pollinators, they rain to the ground and provide a rich source of nutrients for decomposers. Picture-winged flies swarm over the rotting blossoms and rest on vegetation before depositing eggs in the organic stew. Maggots like this one slithering across a leaf are important recyclers of organic matter. Hawaii’s diversity of plants, habitats, and isolation help generate roughly a quarter of all known drosophilid species worldwide.

While visiting the spectacular Tropical Bioreserve and Garden on Hawai’i, we had the opportunity to get up close and personal with one of the many species of drosophilids on the island. Along a forested path in the garden grows a remarkable, bizarre cannonball tree, Couroupita guianensis. This native of Central and South America is often found in botanical gardens around the world by virtue of its stunning blossoms and cannonball-shaped fruit. Trunks of the cannonball tree are festooned with extremely fragrant blossoms and woody round fruits, a stunning presentation of flowers and fruit. When blossoms complete their task of attracting pollinators, they tumble to earth and create a thick slimy carpet of decaying organic matter beneath the cannonball tree, a perfect nursery for developing larvae of drosophilid flies. As I crouched in the stinky goo to photograph some maggots, drosophilid flies swarmed around the vegetation beneath the tree. My efforts were rewarded when I discovered fly larvae slithering across the surfaces of decaying blossoms. Lucky me.

Ah, but all is not rosy for the drosophilid flies in Hawai’i. It turns out that the invasive western yellow jacket we met a few weeks ago finds drosophilids delectable. This predatory rascal is responsible for population collapses of many species of picture-winged flies since the yellow jacket arrived in the Hawaiian Islands. Let’s hope its presence doesn’t seriously disrupt the course of evolution of picture-winged flies and other creatures in this unique evolutionary laboratory.    Hawaiian

Acknowledgements

We thank Dan Gruner for stimulating discussions about the ecology of Hawaiian flora and fauna and Paula Shrewsbury for images used in this episode. The great articles “Sexual Selection and Speciation in Hawaiian Drosophila” by Christine R. B. Boake and “Hawaiian Drosophila as an Evolutionary Model Clade: Days of Future Past” by Patrick O’Grady and Rob DeSalle were used as references for this episode. We also thank the wonderful staff of the Hawai’i Tropical Bioreserve and Garden for creating a great location to observe and enjoy picture-winged flies and tropical plants.

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Last week we met a handsome wasp inspecting galleries in wooden posts at the visitor center in Volcano National Park on the big island of Hawai’i. The keyhole wasp, Pachodynerus nasidens, belongs to a subfamily of cosmopolitan vespid wasps called the Eumeninae, commonly called potter and mason wasps. As we learned last week, keyhole wasps use galleries abandoned by other insects or human-made tubes and hollows as nurseries to raise their brood. Now let’s travel a few thousand miles east back to the DMV to visit another member of the Eumeninae.

Several years ago, an eagle-eyed Master Gardener made an inquiry regarding black and white wasps poking around her mason bee colony. My gardener friend wondered about the identity and intent of these winged wonders. Were these wasps nefarious ruffians out to eat mason bee babies and pillage their pollen cakes? You may recall meeting hard working mason bees in a previous episode of Bug of the Week and seeing photographs of hollow cardboard tubes and holes drilled in wood used to accommodate these industrious early season pollinators. Mason bees are not the only members of the bee and wasp clan that have evolved to take advantage of vacant galleries in wood. These hollow chambers excavated by wood-boring bees like carpenter bees and round-headed beetle borers are used by several species of mason wasps as nurseries to raise their brood.

As adults, mason wasps provide two important ecosystem services, one of pollination as they seek nectar and pollen as sources of food, and another as biological control of plant-eating caterpillars. Unlike the larvae of mason bees that consume pollen cakes supplied by their mothers, mason wasps consume living but paralyzed caterpillars. Prior to the hunt for caterpillar prey, the female mason wasp deposits her egg in the chamber where caterpillars will be stored. She then hunts for prey on flowers, foliage, vegetables, and fruit. Like potter wasps we met in a previous episode of Bug of the Week, female mason wasps use a potent venom to paralyze their pray. Sometimes as many as 19 caterpillars are captured, paralyzed, and used to provision the cell where an egg awaits. Once a sufficient number of prey has been captured, the chamber is sealed with a plug of mud or sand particles. In a remarkable display of gender control, the female wasp is able to lay either a male or a female egg. Due to the shorter developmental time of the male offspring, male eggs are usually placed near the opening of the gallery. Female eggs are placed deeper within the gallery. In this way faster developing males avoid trying to climb over, around, or bore through their sisters on the way out of the nursery.

Mountain mint looks like a super food for mason wasps as they carbo-load in preparation to search for caterpillars. Watch as this female sips nectar from several blossoms before the hunt. Natural holes made in wood by other insects and human-made holes drilled in logs for mason bees make great nurseries for mason wasps. A little tickle with a wisp of wood brings a female out of her nursery. A quick look around reveals nothing amiss and back she goes into the gallery to resume her work. To my surprise, a weep-hole made in the vinyl frame of my living room window makes a great nursery for a mason wasp. After provisioning galleries with paralyzed caterpillars to feed their young, mothers gather balls of mud which will be used to seal the nursery chambers. Using jaws and patience, a female makes a beautiful mudball. With the mudball complete and cradled beneath her legs, she flies back to her nursery. It takes several loads of mud to seal the gallery completely. Here a mother puts the final touches on her handiwork. A solid coat of mud plaster helps prevent enemies from attacking and killing her developing brood. 

So, when you see these magnificent black and white wasps hovering around mason bee colonies, fear not, these are highly beneficial mason wasps looking for an empty apartment as a nursery to raise their brood. They are part of Mother Nature’s hit squad helping to reduce damage caused by caterpillars in our gardens and landscapes. You can make them part of your pest management team by providing them with critical nectar and pollen sources such as gorgeous native mountain mint and spotted horse mint.

Acknowledgements

The wonderful references “Trap nesting wasps and bees: Life histories, nests, and associates” by Karl Krombein and “The Cocooning Habit of the Wasp Monobia quadridens” by Phil Rau were consulted to prepare this episode.  

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Over the past several weeks we meet gorgeous peripatetic butterflies, monarchs and Gulf fritillaries, that somehow found their way to the Hawaiian Islands. Last week fierce western yellowjackets of the vespid clan took center stage as they murdered invasive cockroaches at Volcano National Park. This week we return to the site of erupting Kilauea for a quick stop at the visitor center to meet another member of the vespid clan, keyhole wasps that arrived in the islands by ship in the early 1900’s. Exterior wooden posts at the visitor center bear many holes made by humans and unidentified wood-boring insect. These abandoned galleries now provide a wonderful set of condominiums in paradise for fetching keyhole wasps.

Keyhole wasps are so named for their habit of using empty galleries in wood made by other insects and human-made voids such as keyholes or electrical sockets as nesting sites. They sometimes also nest in abandoned nests of other wasps like mud daubers, or empty silken cases of caterpillars. After thoroughly inspecting, cleaning, and accepting a nest site, the female wasp captures and paralyzes several caterpillars. These living dead are stuffed into the gallery. Mother wasp lays eggs within the gallery and seals the chamber with mud. The fresh meat of paralyzed caterpillars serves as larder for her young as they hatch from eggs and develop. For the hapless caterpillars, what a way to go!

 

Keyhole wasps use holes in wood made by humans and wood-boring insects as nurseries for their young. One little lady inspects a potential nest site and decides it isn’t quite right. An industrious female nearby prepares the nursery by removing trash left behind by former occupants. Once the perfect gallery is cleaned and ready for occupation, it’s off to find and paralyze delectable caterpillars to feed her youngsters. Caterpillars returned to the nursery provide fresh nutritious food for developing wasp larvae that hatch from eggs deposited in the gallery by their fierce mother.

But you don’t have to travel to the Hawaiian Islands to observe these splendid hunters. Keyhole wasps are indigenous to Central and South America and have been found in Mexico, Texas, Virginia, and Florida. They have also made their way to several Islands in the Atlantic and Pacific as well as the continent of Australia. Their arrival in Australia caused a bit of a stir at the Brisbane airport, where keyhole wasps decided that pitots on airplanes created excellent galleries in which to build nests for raising their young. Know what a pitot is? Me neither, but I have learned that these are small hollow tubes on the nose cone of an aircraft used to measure the airspeed of the plane. Keyhole wasps nesting in these tubes plugged them with mud which resulted in “serious safety incidents” as information on airspeeds “critical for landings, takeoffs, and flight became unreliable.” Yikes! By modifying habitats near the airport to disfavor nest-building by wasps, providing alternate nest sites, covering pitots between flights, and inspecting pitots regularly, problems created by these opportunistic invaders have been quelled Down Under. Although keyhole wasps are not yet common in the DMV, a close relative called the four-toothed mason wasp makes its home in the DMV. We will learn a bit more about this interesting caterpillar hunter in next week’s episode.  

Acknowledgements

Fascinating references used to create this episode include “Inventive nesting behaviour in the keyhole wasp Pachodynerus nasidens Latreille (Hymenoptera: Vespidae) in Australia, and the risk to aviation safety” by Alan P. N. House, Jackson G. Ring, and Phillip P. Shaw, and “The Genus Pachodynerus in North America (Hymenoptera: Vespidae: Eumeninae)” by James M. Carpenter.  We thank Drs. Nancy Breisch and Al Greene for assistance in identifying the keyhole wasp, Dr. Paula Shrewsbury for discovering and photographing wasps, and Dr. Dan Gruner for interesting discussions of invasive species in the Hawaiian Islands.

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