Month: March 2023

Last week we escaped the chilly mid-Atlantic to visit the smiley-faced spiny orbweaver in the Everglades of Florida. This week we return to warmth of southern Florida to learn about the largest grasshopper in North America, the eastern lubber grasshopper. With spring off to a fast start in much of the eastern United States, it’s not surprising that eggs deposited in the soil by female lubbers last year have already begun to hatch. What is surprising is the affinity these tiny newborn grasshoppers have for the side of my tent as they warmed themselves in the morning sunlight after a chilly night in the Everglades. Hard to beat an early morning visit from a dozen or so pretty grasshoppers. Nearby, slightly older lubbers were busy defoliating leaves of hairy beggar ticks. Their gregarious behavior and striking coloration of brilliant yellow, orange, or red lines and patches on a jet-black background make them hard to miss.

Tiny lubber grasshoppers warm themselves on the sunny side of my tent while slightly older nymphs dine on leaves of beggar tick nearby. As nymphs age and molt, color patterns may change and wing buds appear just behind the head. As adults, whether it’s a romantic interlude in the sunshine or a stroll along the boardwalk to gawk at humans, heavily armored and chemically defended eastern lubber grasshoppers seem to fear no one.

One would think that these brightly colored creatures that will grow to be one of the largest insects in the United States would evade humans and be wary of enemies, or perhaps employ camouflage to avoid the beaks and jaws of hungry predators. But, oh no, these critters boldly walk, dine, and mate in full sight. How do they do it? What special powers do lubber grasshoppers possess to move about a dangerous landscape with impunity? Let’s revisit some of the remarkable defenses of lubber grasshoppers we described in a previous episode. First, we’ll take a look at some defensive morphologies and behaviors of lubbers. The body of lubbers is protected by sturdy plates of chitin, body armor that can withstand attacks of many smaller predators. As they molt and grow larger, lubber legs are festooned with rows of strong spines capable of piercing human and, presumably, reptilian flesh (but don’t try this for yourself). In addition to spiny legs, the powerful jaws of the lubber could deliver a nasty bite to predators.

The Latin epithet, microptera, found in the species name of this critter literally means “small wing.” Indeed, wings of the lubber are so small they are no longer functional for flight. This locust moves through the world on legs rather than wings. However, the hind wing of the lubber nonetheless serves a very important function. Its brilliant scarlet color serves as a warning to visually astute predators. Those with lubber experience learn that messing with lubbers will result in punishing chemical warfare. The first line of chemical defense, one regularly employed by many insects, is vomit. Across the insect realm from caterpillars to grasshoppers, regurgitation of disgusting gut contents is often employed as a defense when predators attack. As kids we learned that grasshoppers would ‘puke tobacco juice’ (technical terms) onto our fingers and hands when we grabbed them. In addition to staining skin, tobacco juice was kind of stinky. Clever studies revealed that lubbers often dine on plants whose leaves are loaded with bitter secondary plant chemicals. That may be why the vomit of lubbers is repellent to invertebrate predators such as ants.

If this array of defensives tactics is not enough, lubbers have one more trick – repellent froth. When under attack, eastern lubber locusts produce noxious, frothy, foam from a breathing port called a spiracle on the side of their body. This foam is a veritable witch’s brew of aromatic and irritating chemicals that hiss and bubble upon release. Body armor, spines, and chemical weapons help these ancient giants of the grasshopper kingdom survive and thrive in an ever-changing world.     

Acknowledgements

Delightful references including “Large size as an antipredator defense in an insect” by Douglas Whitman and Shawn Vincent, “Secret weapons” by Thomas Eisner, Maria Eisner, and Melody Siegler, and “For the love of insects” by Thomas Eisner formed the factual basis for this week’s episode. Thanks to Dr. Shrewsbury for wrangling and photographing lubber locusts and to the remarkable Big Cypress Nature Preserve and Audubon Corkscrew Swamp Sanctuary for providing inspiration and thespians for this week’s episode.

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After two months of record warmth in the DMV, Mother Nature decided that a late winter chill-down is in order for the greater Washington-metropolitan area. With blossoms of cherries and magnolias in peril and insect activity still in a state of languor, it’s time for a road trip to warmer parts of our nation. First stop, Big Cypress National Preserve in the beautiful, buggy Everglades. While walking along a gator-infested bayou and trying not to disturb any large, sunbathing reptilians, our adventurous party of four almost collided with a magnificent orb web constructed across a swampy trail. At the center of the orb a ghostly face with two black eyes, a broad toothy grin, and a halo of scarlet spines smiled at us. This small but scary spider was the ghoulishly gorgeous spiny orbweaver. Locally known as the Florida crab spider, this species ranges from Florida to Argentina in North, Central, and South America. As is the case with many spiders, at 10 – 13 mm in width, females are much larger than their puny mates, which may be only 2 – 3 mm wide.

Webs of the spiny orbweaver are a masterpiece of functional beauty. Strong non-sticky radial lines support concentric circles of sticky prey-snaring strands. At the center of the web, females rest in an open area of non-sticky lines awaiting arrival of prey. When a fly, beetle, or small moth is snared by a viscous strand of silk, the female plucks radial strands with her forelegs to vibrate attendant sticky strands, which further ensnare her hapless victim. Small prey may be carried by to the center of the web where they are consumed, while larger prey are bitten and paralyzed, then wrapped in silk to await a visit from the fangs of the hungry spider. Yikes!

This ten-foot gator isn’t the only one smiling in the Everglades on a beautiful sunny day. Nearby, a spiny orbweaver has constructed its web. Adorned with scarlet spines and a ghoulish grin, a female boldly awaits a hapless victim to be ensnared by her web. White tufts of silk produced by the spider hang from several radial strands. These tufts may alert birds to the presence of the web and reduce destructive collisions that result in lost time and materials if a bird wrecks the web. These successful predators make their webs not only in the wild but in urban habitats near high rise condos as well.  Gator image by Paula Shrewsbury, PhD.

As you watch the video of the spider in its web, notice the white tufts of silk that adorn several of the radial lines of the web. What purpose do they serve? Well, many of us have experienced the disturbing thud of a bird hitting a large glass window. One way to reduce these unfortunate and sometimes lethal crashes is to paint patterns or attach stencils of birds on the window to alert our avian friends of an impending collision. Scientists believe that the white tufts on the orb weaver’s web may serve the same purpose. Highly visible gossamer tufts make the web more conspicuous and warn birds to steer clear of the delicate strands. While the web poses little peril to a bird, destruction of the web means precious time and material must be spent by the spider to reconstruct its food-snaring trap. With their malevolent smiles and thorny spines to confound predators and web adornments to ward off birds, spiny orbweavers thrive in the great river of grass known as the Everglades.

Acknowledgements

Bug of the Week thanks Jim, Anne, and Paula for spotting the spiny orbweaver and providing inspiration and images for this episode. Two great references “Spiny orb weaver spider, Gasteracantha cancriformis (Linnaeus)” by G. B. Edwards and “Biological and behavioral notes on Gasteracantha cancriformis (Arachnida: Araneidae)” by M. H. Muma were used to prepare this episode.

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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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