Bad at Goodbyes

Rough Transcript

Intro 00:05

Welcome to Bad at Goodbyes.

On today’s show we consider the Palma Stick Grasshopper

Species Information 02:05

Palma Stick Grasshopper are among the largest in the world, with males as large as 3.5 inches long and females reaching lengths up to 5 inches long. Their cylindrical bodies resemble twigs or sticks, which lends them their common name.

Their coloration is a mottled blend of brown, gray, and green, which also camouflages them in the vegetation of their habitat. It is pretty uncanny, I encourage listeners to look up images of the Palma Stick Grasshopper, the camouflage is super effective.

Their strong exoskeleton, a kind of segmented protective armor, is covered in sensitive hairs for detecting sound vibrations and air currents, alerting the grasshopper to the rustle of leaves by a predator or the calls of other insects.

Their body is divided into three main sections: the head, thorax, and abdomen. 

The head is relatively small and round, seamlessly blending into the thorax. A pair of compound eyes protrude from the upper sides of its head, allowing for nearly 360 degree vision. Between the eyes is a pair of very long spire-like antennae which are covered in thousands of tiny sensory receptors to detect chemical cues in the air, like the pheromones released by potential mates, and for identifying suitable food sources and detecting predators. At the bottom front of the head is the grasshopper’s mouthparts, which to my layperson’s eye look like a pair of lips, and pretty kissable lips at that. But there’s a lot more going here than looking cute.

Palma Stick Grasshopper mouths have four main parts the Mandibles, Maxillae, Labrum and Labium

The mandibles are paired, strong, sharp scissor-like structures, one on each side of the mouth. Each mandible is attached to the head by a multi-flex joint, allowing for precise manipulation of food and opening and closing horizontally (unilke our jaws which move vertically). The inner edges of the mandibles have sharp incisors for cutting and tearing the shoots and leaves that the herbivorous grasshopper eats. The molar region, located further back, has a ridged surface for crushing and grinding the plant material.

The maxillae are paired structures located behind the mandibles that aid in holding and tearing food and guiding food toward the mouth. The Maxillae palps are like mini-antenna equipped with taste receptors. The maxillae work in tandem with the mandibles; while the mandibles perform the primary cutting and grinding, the maxillae hold the food steady, and taste it for flavor and viability.

And then Labrum and labium can be thought of as the top and bottom of the grasshopper’s mouth. They both help guide food into the mouth and the labium can close upward, preventing food from falling out when chewing. Labial palps, like the maxillary palps are two tiny curve appendages used for tasting.

The Palma Stick Grasshopper is a very specialized feeder, consuming only three total species of plant. Less than a quarter of its diet is split between the Canary Island Pine and the Canary Island Broom. And then the remaining three-quarters plus, consists of the new leaves and tender shoots of the Canary Island Spurge.

It’s worth noting that the Canary Island Spurge contains a toxic sap. But the Palma Stick Grasshopper has evolved a tolerance to these toxins, allowing it to consume this otherwise unpalatable food source.

It eats poison with its scissor-mouth, so like: Don’t kiss the grasshopper.

So that’s the head, onward to the thorax, the middle section of the grasshopper’s body. All six legs, three on each side, grow from the thorax. The forelegs and midlegs are short-ish and thin, and the hind legs are thicker, longer and powerful. Those are the jumping legs though the Palma Stick Grasshopper’s jumping ability is limited compared to other grasshopper species due to their large body size. And unlike many grasshopper species, the Palma Stick do not have wings, so though they can jump short distances, their primary mode of transportation is walking and climbing.

Okay, that’s the head, thorax, and now lastly, the abdomen. The abdomen is the widest and longest section of the body and contains the digestive, respiratory and reproductive systems. In female Palma Stick, the abdomen is notably larger, holding the large number of eggs they produce and the ovipositor, a specialized structure used for laying those eggs. Palma Stick Grasshopper are sexually dimorphic, meaning there are distinct physical differences between females and males beyond just the reproductive organs. In this case it is size. Females are generally roughly twice the size of the males.

Female Palma Stick Grasshopper sound to attract mates. The grasshopper has a tiny, hard plate connected to the side of its thorax by a flexible membrane. When it contracts this section of its thorax, the plate rotates, bumping against a ridge on its underside, creating a clicking sound. When the grasshopper relaxes its thorax the plate spins back creating another click. In repetition it creates a rhythmic mating call to attract males.

It sounds like this.

[Palma Stick Grasshopper clicking sounds]

Males will follow the song and if receptive, the female will allow the male to mount her back and initiate copulation. During mating, the male transfers a sperm packet, or spermatophore, to the female’s reproductive tract.

After mating, the female Palma Stick Grasshopper lays her eggs in the soil beneath the Canary Island Spurge. She carefully selects a suitable location, often near the base of the plant, where the eggs will be protected and the emerging nymphs will have access to their food source. The eggs are encased in a protective frothy substance that helps to maintain moisture and safeguard them from predators and environmental fluctuations. 

Embryonic development within the buried eggs can take up to several months and then once the nymphs hatch, they emerge from the soil and begin feeding on the spurge leaves. As they develop they undergo a series of molts, shedding their exoskeleton as they grow. It’s estimated that they undergo around six molts before reaching adulthood. Each molt represents a significant step in their development, allowing them to increase in size until they reach adulthood and are ready to reproduce themselves. This process takes about two years.

————

In the dream grasshopper

Hides behind the branch, my lover

Dresses for the day

In the dream.

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Adult Palma Stick Grasshopper have not been observed exhibiting robust social behavior and are generally solitary outside of mating. They are primarily diurnal, meaning they are most active during the daytime. And they are ectothermic, meaning they rely on external sources of heat, like the sun, to regulate their body temperature. So they spend the warm daylight hours foraging and feeding and then at night, they shelter among the foliage, reducing their exposure to predators and conserving warmth.

They exhibit a kind of shyness, and a deliberate, slow pace; they rely on their camouflage and subtle movements to avoid detection by predators. And detection by scientific observers. Grasshopper expert and entomologist Heriberto López who has studied the Palma Stick extensively writes

Quote:

”this species … moves very slowly, [and] rotates around the branch on which it stands when it perceives some near activity, interposing the branch between itself and the subject of the movement; In this way it hides from the sight of any stranger. In order to increase the success of detecting specimens, we used two observers per plant at the same time, which allows detecting the individuals that moved, hiding of one of the observers”

So Dr. Lopez’s field team would go in pairs, and one observer would wait quietly near a Canary Island Spurge plant and the other would make a bunch of noise on the other side. And the quiet observer could then more easily see the grasshopper and do field counts as it turned to hide from the noisy scientist.

The Palma Stick Grasshopper, is native to the island of La Palma, one of the westernmost islands in the Spanish Canary Archipelago, located off the northwestern coast of Africa.

The Canary Islands were formed through volcanic activity over millions of years. The islands are the result of a hotspot, a plume of hot magma rising from deep within the Earth’s mantle, building up layers of lava on the ocean floor, eventually emerging above sea level to create the islands. This process began 70 million years ago and the island of La Palma began to emerge above the ocean’s surface about 2 million years ago.

So like the island, layer of cooled lava, upon layer of cooled lava, over and over for 68 million years, like impossible paper mache, builds up from the ocean floor, finally crests the ocean waves. And then because we live on a miraculous earth, life, plant and animal life blossoms there and evolve particular adaptations to this unlikely landscape.

The Palma Stick specifically is found only in roughly 12 square miles, on the southwestern edge of La Palma. This is an arid scrubland biome, characterized by sparse vegetation, volcanic rock formations, and dry, dusty slopes, with expanses of lava fields, cinder cones, severe coastline cliffs and black sand beaches. Plant life is primarily drought-tolerant shrubs and succulents, with scattered patches of grasses and herbs.

This is a climate with warm, dry summers and mild, marginally wetter winters. Summer temperatures will reach highs in the 90s, while winter lows rarely dip below 50. The annual rainfall is relatively low, averaging between 12-16 inches, with most of that precipitation occurring during the winter months.

The Palma Stick Grasshopper shares its island home with Canary Island White Butterfly, Laurel Pigeon, Sweet Tabaiba, Ladybug, Thymelaea, Wild Madder, Canary Big-eared Bat, Common Kestrel, Canary Island Gecko, Canary Island pine, Incense Plant, Blue Chaffinch, West Canary Lizard, Cory’s Shearwater, Canary Island Sorrel, Dragonfly, Loggerhead Sea Turtle, Honey Bee, East Canary Skink, African Blue Tit, Red Admiral Butterfly, Canary (from which the islands get their name), of course Canary Island Spurge, and many many more. 

Habitat loss and fragmentation pose the most significant challenge to the grasshopper’s survival. Its dependence on the Canary Island Spurge makes it highly vulnerable to changes in the ecosystem. Historically, land clearance for development or agriculture have significantly reduced the availability of suitable habitat, drastically reducing and fragmenting the grasshopper population.

Today, continued development, illegal logging in order to expand grazing areas, and overgrazing by introduced domestic species, further threaten the grasshopper’s scrubland. Introduced invasive plant species also pose a risk of outcompeting the Canary Island Spurge, reducing available food and shelter for the grasshopper.

Relatedly, human induced climate change is altering both temperature and rainfall patterns, impacting both the Palma Stick and the Spurge plant it relies upon.

The Palma Stick Grasshopper is legally protected, included as “Endangered” in both the Spanish National and the Canary Regional official lists of threatened species and most of the population is in protected natural areas, the Tamanca Protected Landscape, and the Cumbre Vieja Reserve.

Nevertheless the Palma Stick Grasshopper has been considered critically endangered on the IUCN Red List since 2012 and their population is currently in decline.

Our most recent counts estimate that less than 200 Palma Stick Grasshopper remain in the wild.

Citations 22:59

Sound recordings by Heriberto López from the Orthoptera Species File Online – http://orthoptera.archive.speciesfile.org/Common/basic/Taxa.aspx?TaxonNameID=1116906 

American Museum of Natural History – https://www.amnh.org/learn-teach/curriculum-collections/biodiversity-counts/arthropod-identification/arthropod-morphology/front-view-of-an-insect-grasshopper-head 

Bulletin of Entomological Research, Volume 97, Issue 2 – https://doi.org/10.1017/S0007485307004828 

Conservation Genetics vol 8, issue 3 – https://doi.org/10.1007/s10592-006-9199-5 

Group of Entomological Research from Tenerife – https://www.speciesconservation.org/case-studies-projects/la-palma-stick-grasshopper/10202 

IUCN – https://www.iucnredlist.org/species/15038553/175765678

Journal of Zoology. Volume 275 issue 1– https://doi.org/10.1111/j.1469-7998.2007.00394.x 

Museo Nacional de Ciencias Naturales of Spain – https://digital.csic.es/handle/10261/174040 

Wikipedia – https://en.wikipedia.org/wiki/Pamphagidae

Music 24:28

Pledge 29:04

I honor the lifeforce of the Palma Stick Grasshopper. I will carry its human name in my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species.

And so, in the name of the Palma Stick Grasshopper I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant or animal kin or their habitat, by individuals, corporations, and governments.

I pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.