Month: April 2022

On a rare 70-degree day two weeks ago, good fortune found me on a pleasant promenade that connects New Jersey Ave. and 4th Street south of the US Department of Transportation in Washington DC, a section of the city known as Navy Yard and which serves as the home of the Nationals baseball team. A beautiful water feature graces the promenade and this urban refuge is shaded by golden rain trees, Koelreuteria paniculata, beautiful ornamental trees widely planted in landscapes throughout North America and worldwide. These sturdy trees are favored in urban landscapes by virtue of their ability to withstand a variety of growing conditions and soil types. Their ornamental value comes from large clusters of bright yellow flowers displayed from summer into fall. In autumn the flowers produce interesting clusters of showy, papery seedpods. The seedpods are reddish-purple when developing and turn brown as they mature. Several ebony seeds are produced within each pod. Legions of seeds rain down to earth beneath the golden rain tree. Sturdy shells inhibit degradation of the pods in winter and a nutritional bounty remains in spring. 

Our southern and gulf-coast states are home to several native plants belonging to the golden rain tree family of plants, the Sapindaceae, commonly called soapberries. A striking insect called the red-shouldered bug, or golden rain tree bug, has evolved to use the seeds of soapberries as food. Golden rain tree bug is a “true” bug identified by its sucking mouthparts, young that are called nymphs, and half-leathery, half-membranous front wings. Jadera belongs to the clan of true bugs known as scentless plant bugs or Rhopalidae. We met other rhopalids in previous episodes including boxelder bugs and curious Niesthrea lousianica, the eater of mallows. Historically, red-shouldered bugs occupied neotropical realms in Central and South America, and in North America were found primarily in southern states including Florida, Texas, Arizona, and California, where they dined on native soapberries. 

On a promenade in Navy Yard, red-shouldered bugs scramble across the pavement and scale rain trees while playing the mating game. The guys seem to have a hard time keeping pace as females lead the way. Potential interlopers access their options and quickly move along. When it comes to dining, red-shouldered bugs are a chummy lot as they share meals of rain tree seeds.

The introduction of golden rain tree to our country in the 1700s provided an excellent opportunity for the red-shouldered bug to try Asian cuisine. Golden rain tree is now one of the favored foods of this bug throughout our country. During the past century, red-shouldered bugs have made a steady march northward, discovered in North Carolina in 1938, Virginia in 1987, and Maryland in 2002. Scientists believe that milder winters associated with climate change facilitated the range expansion of red-shouldered bugs into regions where chilly winter temperatures previously excluded them. As I walked the golden rain tree promenade, dozens of red-shouldered black bugs milled about on the ground feasting on fallen seeds, scrambling up trees, and basking on sidewalks. While hordes of bugs were a source of delight for me, so many bugs in one place night unnerve other visitors to the Yard. 

As the weather turns warm, these red and black beauties will mate, lay eggs, and feed on the bounty of the rain tree. Using their beak, nymphs and adults pierce the tough seed coat and probe the nutritious meat of the seed. Digestive enzymes pumped through the beak into the seed break down proteins, fats, and carbohydrates. Once liquefied, these nutrients are sucked back up the beak and into the gut of the bug where they are converted to proteins used for growth and reproduction or broken down to supply the energy for all the running about and mating that occupies the time of these bugs. These bugs have been known to enter buildings in autumn when the weather finally turns cold and bugs seek shelter. In the wild, shelter might be a fallen log, a pile of branches and leaves, or a rocky outcropping. In their new urban home, winter shelter for the red-shouldered bug might be one of the many dining establishments or agency buildings found in Navy Yard. Will they appear in other venues, maybe in center field at Nats Park with humans wearing red? Probably not, but only time will tell.

Sometimes the simplest tasks, like transporting a soapberry, get complicated when you’re a bug.

 Acknowledgements

 We thank members of the Pick lab, Jackie, and Others Coffee for providing the inspiration for this episode of Bug of the Week. “Jadera haematoloma, Another Insect on its Way North (Heteroptera: Rhopalidae)” by Richard L. Hoffman and Warren E. Steiner, and “Specialization of Jadera Species (Hemiptera: Rhopalidae) on the Seeds of Sapindaceae (Sapindales), and Coevolutionary Responses of Defense and Attack” by Scott P. Carroll and Jenella Loye, were consulted in creating this episode.

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Last week we visited industrious harvester ants in the Mojave Desert. While patrolling these arid lands, we met a plant guru and long-time resident of the Mojave who shared a tale of colorful caterpillars embedded in silken webs on a beautiful native shrub called desert almond, Prunus fasciculata. Desert almond was flora incognita to a Bug Guy from the East Coast, but our desert naturalist shared that fruits of desert almond are highly attractive to many resident birds and rodents and edible to humankind as well. Native Americans of the region, including those of the Cahuilla Nation, consider them a delicacy.

With a vague notion of what desert almond plants looked like and a strong desire to taste their curious fruits and see caterpillars, we set out across the boulder-strewn moonscape in search of caterpillars and almonds. In less than a mile, we stumbled across a sweet smelling, tightly branched shrub festooned with silken webs. As the late afternoon sun warmed their tents, dozens of beautiful western tent caterpillars snuggled together amidst the unseemly remains of pelletized former meals. Excrement of insects is politely known as frass. These leaf-munching tent-makers bore a striking resemblance to their cousins, eastern tent caterpillars, which we visited in previous episodes.  Western tent caterpillars, as their name suggests, occupy western regions of North America ranging from Alberta, Canada to the southern deserts of California and Arizona. Winter is spent as eggs deposited by the hundreds in a dark Styrofoam-like mass encircling a small branch. With the warmth of spring, eggs hatch and tiny caterpillars dine on tender leaves and build their characteristic webs. In addition to desert almond, western tent caterpillars dine on other members of the rose family, including cherries and apples, and also on alders, oaks, poplars, and willow. From their silken bivouac, larvae move along branches to the newly expanding leaves to feed. As larvae grow during spring, they enlarge their silken tents. Tents help caterpillars conserve heat as the writhing mass of caterpillars elevates the temperature inside the tent. Higher temperatures accelerate growth and development of caterpillars on chilly spring days. Their silken homes may also provide protection from predatory or parasitic insects.

The starkly beautiful Mojave Desert is home to a rich diversity of plants and animals. Desert almond shrubs, kin to our domestic almonds, cherries, plums, and peaches dot the landscape. Western tent caterpillars festoon branches of desert almonds with silken webs. A peek inside a tent reveals a messy scrum of wiggling larvae amidst strands of silk and pellets of excrement called frass. Outside the tent mature caterpillars cruise branches in search of fresh leaves.

Near the end of larval development, caterpillars go solo and forage on their own. With growth complete, caterpillars pupate within the confines of their tents or wander from plants seeking protected spots beneath logs, leaves, stones, or human-made structures to spin yellowish or white, silken cocoons. While the desert almonds we visited in the Mojave seemed not to be overwhelmed by western tent caterpillars, other species of tent caterpillars, including the forest tent caterpillar and eastern tent caterpillar, can be problematic when cyclic, outbreaking populations strip trees of foliage. In a previous episode, we provided some easy ways to deal with tent caterpillars when they get out of hand on trees and shrubs in residential landscapes.

Although our quest for western tent caterpillars was a success, the chance to dine on desert almonds was, well, a failure. We arrived in the desert just a bit too early in the season and desert almonds still in bloom had not yet produced fruit. Of course this provides a perfect excuse for a return visit to this remarkable realm.      

Acknowledgements

“Western Tent Caterpillar” by the USDA Forest Service and “Population fluctuations of the western tent caterpillar in southwestern British Columbia” by J. H. Myers were consulted in preparation of this episode. We thank Dr. Shrewsbury for spotting and wrangling western tent caterpillars and Robin and Max at the High Desert Eden for sharing their tent caterpillars with Bug of the Week.

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With weather still a bit dreary in the DMV, let’s travel to the Mojave Desert in southern California to warm up and meet some really cool desert denizens, harvester ants. In previous episodes we visited home-invading odorous house ants as they raided pantries in search of sweets and herded honeydew-squirting aphids on peony blossoms outdoors. Unlike many ants that carbo-load on nectar and honeydew, harvester ants thrive on long chain and complex carbohydrates, lipids, and proteins found in the seeds of plants. These ambitious foragers get their name by harvesting seeds that serve as the major source of food for their colony. Red harvester ants greet the day by sending patrollers from the hidden depths of the colony to inspect the area immediately around the colony and beyond to distances up to a 20-minute ant-walk away. The return of patrollers signals the colony to muster forager ants to begin the busy task of collecting seeds from nearby plants. These dauntless workers may spend up to an hour on their journeys and venture 20 meters from the colony to collect seeds and bring them back to subterranean granaries in their colony.

On a sandy road in the Mojave Desert, a colony of harvester ants works at a fevered pitch. Watch as they collect seeds for their granary and excavate sand to enlarge their subterranean home. Harvester ants play a key role in dispersing seeds of many plants in the high desert.

Seed harvesting is not entirely bad for desert plants as some seeds are lost along the way home during peregrinations of foragers. Some accounts tell of seeds sprouting in over-filled harvester ant galleries, giving rise to new desert plants. Either way, harvester ants are important seed dispersal agents for propagules of many different species of plants. In fact, some plants have taken this relationship to a higher level and produce seeds with elaiosomes, structures packed with lipids, proteins, vitamins, and other nutrients that are highly attractive to ants. This form of ant-assisted seed-dispersal is known as myrmecochory. Why would plants make an evolutionary investment to manufacture energy-rich dispersal structures for their seeds? Scientists provide evidence that seed-dispersal by ants may reduce competition between parental plants and their offspring or competition between their offspring and other species of plants. Dispersing seeds may also derail gluttonous seed-eaters like small mammals that might devour an entire crop of seeds concentrated beneath a parental plant. Also, ant colonies often occupy nutrient rich pockets of soil where plants can thrive. Convincing ants to carry their seeds to these favorable microhabitats is a clever move on the part of a plant.

Red harvester ants are known by many as the entertaining occupants of “ant farms” sold to children and schools. Ant farms are engaging and educational but, as some have learned firsthand, harvester ants can pack a memorable sting. On the famous and amusing Schmidt sting pain index, pain associated with the sting of red harvester ants is described as “Like using a drill to excavate your ingrown toenail.” Yikes! Having said this, I will share that as I photographed and recorded harvester ants for this episode, dozens of ants explored my hands, arms, and body without delivering a bite or sting. Lucky me, I guess.

Acknowledgements

We thank our hosts Robin and Max at the High Desert Eden for sharing their harvester ants, stars of this episode. Two remarkable references, “The Regulation of Foraging Activity in Red Harvester Ant Colonies” by Deborah M. Gordon, and “The Ants” by Bert Hölldobler and E. O. Wilson, were used to prepare this episode.

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Recently we met two very large orb-weaving spiders, the golden silk spider and the Jorō spider, one of which, the Jorō, seems poised to expand its range northward along the eastern seaboard. But guess what? We already have several other impressively large spiders that are native residents in the DMV. Recently I received a text message from a friend with an image of a beautiful large fishing spider snuggled in the folds of a bedroom drape. Whether the spider had been loafing indoors all winter or simply moved in during a brief warm spell remains a mystery. Nonetheless, this oversized arachnid certainly left a memorable impression on my friend.  

Fishing spiders, in the genus Dolomedes, are often found near or on water, but they also wander forests and suburban landscapes and make startling appearances in homes and outbuildings. On more than one occasion, fishing spiders have greeted me in the basement or when I opened the door of my tool shed. Fishing spiders do not build webs to capture prey. They actively hunt and consume a smorgasbord of aquatic and semiaquatic animals; vertebrates such as fish, tadpoles, and toads, and a wide variety of invertebrates, with damselflies, water striders, aquatic beetles, and midges commonly on the menu. As with many other species of spiders, they have the somewhat disturbing propensity to eat other members of their species including youngsters and, for the females, their suitors. Fishing spiders are patient, clever hunters. With hind legs anchored on shore and forelegs outstretched on the water, they capture prey on and just below the surface when hapless victims venture too near. Special non-wettable hairs on their legs allow fishing spiders to ride the surface tension of water, enabling them to run or sail across the surface of a pool or stream.  

High on the Massanutten Mountain of Virginia a bench sits near a gentle stream, home to remarkable numbers of large fishing spiders. While the Zen-like tranquility of this spidery sanctuary may appeal to arachnophiles, arachnophobes may choose to relax elsewhere.

Members of the pisaurid clan also go by the name of nursery web spiders, so called for their habit of building a small web to serve as a refuge for tiny spiderlings emerging from an egg sac. Accounts suggest that fishing spiders can deliver a bite of similar severity to the sting of a bee or wasp. My experience with fishing spiders is that they are quite docile and willing to pose politely for photographs. However, I am not recommending that you try handling one. What of my friend and her fishing spider? She grabbed her handy spider-catching-cup, scooped up the spider, and released it back to the wild, a happy ending for human and spider.     

Acknowledgements 

Bug of the Week thanks Diane for sharing her image of a home invading fishing spider and providing inspiration for this episode. The excellent article “Prey use of the fishing spider Dolomedes triton (Pisauridae, Araneae): an important predator of the neuston community” by Manfred Zimmermann and John R. Spence provided a detailed dietary account of a common, widely distributed fishing spider.  

To see a fishing spider capture a minnow, please click on the following link: https://www.youtube.com/watch?v=nEKRWEo1PSI

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