On the northwest corner of Montezuma Mesa, Marshal Hedin and I are easing down a steep stairway, scorched by the noonday sun. A biology professor at San Diego State, Hedin specializes in arachnids. He’s already described to me several of his favorites: the jumping spiders of the Southwest deserts, the bolas spider, the peacock spiders of Australia. Spiders fascinate Hedin, a 20-year biodiversity researcher. He wants to know how venoms or webs or geographic distributions evolve. The most curious arachnid for him — and San Diego-centric — is the trapdoor spider. Lucky us, they’re on campus.
While descending handrailed stairs, we’re searching for the trapdoor’s burrows, six-inch tubes dug into the ground within the hillside chaparral.“There’s one,” he says. “See it?” His normal gentle matter-of-factness is suddenly keyed-up.
I don’t see it. I’m looking for the spider, not its home. That home, sunk ten inches into the ground and made of silk and dirt, is gated by a trapdoor the size of a nickel. At night, while holding the door slightly ajar, the spider senses vibrations from bugs crawling by, pops the lid open, grabs the prey with its four fat front legs, fangs the catch, and tunnels it down its tubular dungeon for a meal. The rude seizure happens in under a second. (So shows a YouTube video.)
Hedin reaches down and flips open a trapdoor, and we behold a comical scene. The spider, finding no prey but the point of a pocket knife, immediately pincers the door on its underside and pulls it shut. It’s pissed. I glimpse this agitated arachnid, whose color is that of a cockroach’s chitin. I recoil at its hairy legs — shades of tarantula.
This is the only live burrow we come across; the precipitous incline houses a dozen or more abandoned burrows, one of which Hedin digs out and gives to me. He calls it “an engineering marvel.” The silk tube is like a finger of a glove, the material diaphanously thin but sturdy as soft leather.
Ascending the stairs, we see more desiccated burrows, left behind for reasons he’s trying to understand. One clue: these spiders are among the least mobile of all arachnids. The females live and die in situ. The males who feel the mating urge during October rain lumber all over the paved campus, looking for dates.
Even though the county is rich in spiders, especially in the coastal sage scrubland on bases Pendleton and Miramar, the trapdoor is “incredibly stressed.” Hedin says that with this spider, “we’re seeing evidence of either abundance, decline, or complete population extinction.” In the Los Angeles basin, he notes, museum records show they once thrived. The cause of their current diminishment? “We can’t say it’s climate change per se. But it’s a cumulative effect of fragmentation and overall habitat degradation.”
Hedin says that others in Southern California are seeing similar declines. Fragmentation is driving the decay. Spiders are divided, via the human sprawl, into “little pockets,” backyards and canyons becoming makeshift habitats. “As those pockets become smaller, populations just blink out.”
Another common stressor is fire. Insects and spiders may escape the flames but, often, not the heat. As fire sweeps by, they are baked in their hovels and nests.
Studying the stressors that lead to declines in population and number of species (in the world, there are 34,000 spiders identified, 144 in the county), local entomologists and naturalists are crying foul over a multitude of factors: human incursion, planetary heating, loss of habitat richness, shifts in predator orders, pesticides, and an international transmigration of invasive insects (think ants, borers, beetles, mites) that devour native insects or upset the ecological balance for them. All these things stew in the environmental pot, especially in the Pacific trade crossroads of San Diego.
What happens when the bees, butterflies, and beetles who pollinate 75 percent of our food crops, which are also the crops animals eat, become critically endangered? Answer: we start hand-pollinating as the Chinese have begun to do, enlisting laborers to do the flower-by-flower work of the bugs. Or else we find something else to eat.
The lay of the local bug
For eleven years, Dr. Geoffrey Morse and his insect biology class at the University of San Diego have surveyed the entomological diversity of a small sloped area behind the Science and Technology building on campus. They trap, identify, and calculate the bug presence. Eleven years ago, he says, “We got more insects than we could deal with. The last four years, we don’t have enough to make a whole class out of it.”
Why the downturn? A seven-year drought is one cause, and last winter’s rain didn’t restock the numbers. If dry years outpace wet, Morse says, declining plant and insect communities accelerate each other’s fall. “When temperatures increase, that adds another stress. So: bring in water stress, bring in food stress, bring in heat stress. We have insects adapted to a maritime climate. It never gets that hot here, it never gets that cold here. If you change that, the risk is, you close the door to natives and you open the door to nonnatives.”
To quantify the loss of arthropods in our midst is to face several barriers. Michael Wall, head of entomology at the San Diego Natural History Museum, tells me the first problem is that so many insects “are really, really small, dust-sized, in fact.” Creatures like midges and mites, devilish parasites less than 1 millimeter in size, are observable only under a microscope. Most bugs range from 1 to 10 millimeters, with the largest portion on the low end. (Studies in North Carolina and Pennsylvania determined that in a five-inch layer of one acre of farmland topsoil, there are between 124 million and 435 million animals, the majority being mites.)
The second problem is that because of this tininess, it’s the larger, colorful, space-invading bugs — monarchs and swallowtails, the intricate webs of spiders — that capture our attention and, thus, remind us of their fecundity.
But even our interaction with the showy insects is diminishing. One empirical way we know this is the “windshield phenomena,” the number of splats your car’s windshield collects driving to El Centro. A recent German survey, cited in The New York Times, is alarming: “The overall abundance of flying insects in German nature reserves... decreased by 75 percent over just 27 years.” (Anecdotal evidence from the scientists and naturalists I interviewed is roughly the same as the German measure. In addition, anyone can watch streetlamps and neon signs for what used to be a flurry of moths, flies, and mosquitoes. It’s their absence you’ll see, as if the circus has left town.)
Third, as Wall describes in his sunny third-floor office looking out on the park’s massive Moreton Bay fig tree, “We don’t have a good understanding of what the local stressors are on insects.” One reason: the collection at the Nat, for a century the “keeper of our region’s ecological record,” reflects the particular interests of previous curators. In short, over-focus on butterflies and under-focus on “systemized plots” of the non-showy bugs, those insects often too small to pin to a mat. The result: few broadly defined databases or baselines of the arthropods are extant. These “standardized protocols” will, Wall hopes, fill out that sizable absence.
A fourth barrier to understanding species shifts is a kind of Kafkaesque portrayal of insect decline itself. Because we have so many invasive bugs, these marauders obliterate some native species and ramp their own numbers up, exponentially. In a sense, it’s a trade-off, pound for pound, which recasts our traditional biomass. Though it’s difficult to measure biomass, we know that for plants that require insect pollination and for certain vertebrates that require a known food supply, the alteration can be devastating.
Wall has an example. The nonnative crawfish (introduced by anglers as bait) now populate standing pools in many local canyons. They feast on larvae, particularly those of the native dragonfly. Those larvae, fledged as dragonflies, eat the mosquito larvae, which are native as well. It’s not good that the invasive crawfish eats the predator who eats the mosquito babies. That mosquito-dining dragonfly is our friend, an essential devourer, devoured by a nonessential devourer. Entomologists at the University of California Riverside have found that when the middlemen dragonflies are gone, the mosquito population proliferates like junk mail.
Whither the Quino checkerspot butterfly?
Looking for butterflies is among the most rewarding experiences naturalists can have. It can also be among the most depressing. Take the monarch, whose great orange-and-black migratory parade gets them noted and counted. When their numbers, fluttering en masse across the continental United States, shift from few to fewer to oh-no, the sky is truly falling.
David MacNeal, the author of Bugged: The Insects Who Rule the World and the People Obsessed with Them, documents that 20 years ago, one billion monarchs migrated annually from Texas to Minnesota. Today the count is 56.5 million. That’s a 94.35 percent loss.
Sadly, such figures are relative. We’d be thrilled to have 56.5 million of one or all of our county’s threatened butterflies. To survey an endangered example, I’m headed into the San Diego National Wildlife Refuge with U.S. Fish and Wildlife Service biologist John Martin. The encyclopedic Martin, tan-uniformed with leather anti-snake-bite leggings, oversees the flora and fauna of this 12,300-acre set-aside east of Sweetwater reservoir. Climbing up and down steep grades at a turtle’s pace in a wizened truck, we’re cab-jostling to a spot where the Quino checkerspot butterflies congregate, mate, lay their larvae, and after three weeks of frolic, die.
The Quino, once prevalent in Southern California, was thought extinct 30 years ago, then showed up one day in the refuge. Where had it been? It neither migrated nor hid, Martin explains. It was dormant. The butterfly, with its tile-like pattern of orange and white black-bordered squares, was only “appearing to disappear.”
The Quino’s eggs are lain in a larval host called Plantago erecta. It’s a dwarf plant of blue-green color that Quino caterpillars eat. In most rainy seasons, the caterpillar digests enough Plantago to pupate, become a chrysalis, and emerge as a butterfly. In years without much rain, which curtail the Plantago’s life, the caterpillars crawl inside a nearby bush for what’s termed diapause or quiescent sleep: They wait until the next season, or longer, before completing their evolutionary orders.
As if to ratchet down my expectation, Martin says, “I guarantee you we won’t see any Quino. Not in this season.” Before the recent drought, he saw the Quino, abundant in “double figures.” Then, in the rainless years, probing half-a-dozen prime spots, he saw none. For seven years. “I panicked.”
On one of the Quino’s promontories, we step on rocks to avoid breaking the “crypto-biotic crust.” All around us spikes another bug eraser: invasive nonnative grasses. These push out, or limit, the Plantago erecta, a change, Martin notes, that will “convert coastal sage scrub to nonnative grassland,” a food source butterflies can neither propagate in nor eat. Thus, his marked worry and their vulnerability. In a generation, the Quino’s habitats have decreased by 75 percent and its numbers by 95 percent. It’s been federally endangered since 1997.
Add to that the missing-in-action Hermes copper butterfly, its apricot color stippled by black dots, a species endemic to San Diego county. Martin says they fluttered freely in these hills for more than 100 years until most were roasted in the 2003 and the 2007 fires. A candidate for federal listing, they’re not all gone, but they will require a long time to re-colonize.
After two hours of squatting and chatting and imagining what’s not here, at least in dry September, we leave the hilltop, espying waves of suburban development on distant mesas.
The protection racket
The “bug,” speaking strictly, is a Hemiptera insect. To its order belong creatures with “piercing and sucking mouthparts,” so says the Oxford English Dictionary. All insects and spiders reside in the phylum Arthropoda, which accounts for four-fifths of animal life. The Golden State has the greatest arthropodan biodiversity in America, and San Diego county, the greatest arthropodan biodiversity in the state.
Despite this hoopla, significant insect declines amid significant biodiversity amid significant bug invasions is a complex local story — numbers drop and numbers rise, only to confuse us with eerie fluctuations and real disappearances. To that, add the fact that declines are less noticeable when there are so many different insects. Then, when the legions of invasives arrive and bore into our awareness, species hegemony goes topsy-turvy.
The strength of the environmental movement — to save the endangered by saving their habitats — is also its weakness. While California has beefy laws to protect species and habitats, the Nat’s Michael Wall says, “in my view, the state is very focused on listed species.” We are not, in monitoring our biodiversity, insect-centric. Not yet. The question the Federal Endangered Species Act of 1973, which includes fish, insects, birds, reptiles, and mammals, and which has been amended and expanded on the federal and state levels many times, boils down to this: How does the juggernaut of development — urban, suburban, trolley expansion, amusement park, mini-mall — impact listed species?
Today, on the California list, we have 188 species, a number which includes one grasshopper, four bees, five beetles, and 18 butterflies. Ants, wasps, moths, and crickets are not threatened, not because their numbers are high but because we don’t know their numbers. Bugs are the hardest animals to count, Wall says. “We don’t truly know what’s rare and what’s not rare when it comes to insect diversity.” That cloud of imprecision also “does not capture what the impact on the ecosystem is.”
What, he asks, is the value of insects? Wall says the government labels value from an “ecosystem services perspective.” In other words, we measure what insects “do to improve the quality of our life.” How do we marshal and emphasize value and critically link insects and habitats in a complex and interdependent ecosystem?
An ecosystem supersedes any single abundant or endangered species. Such a system is primarily its habitat, say, the entire coastal sage scrubland, in which vulnerable and threatened species can exist and flourish. The near extinction of the California condor is a great example. The bird, critically endangered since 1967 and extinct in the wild in 1987, has been saved via captive breeding. Pairs have been set loose in California and other southwestern states; U.S. Fish and Wildlife says that 446 now exist in the wild and in captivity. Without questioning the salvific effort, how do we gauge the importance of this vulture, with its ten-foot wingspan and voracious appetite, to the ecosystem in which it was once the king of the scavengers?
For insects, Wall comes at this question of value through a back door. Using the protections already in place for listed species, it is possible, he says, that the bugs on which fish, reptile, bird, and mammal species must feed will, if added as ecosystem partners, need the same status as any other essential species. The goal is to sustain a new ecological balance for what’s left — after declines and invasions become the norm. The least Bell’s vireo, an endangered California bird, is an insectivore, dwelling in riparian habitats. Saving the least Bell’s vireo has to include saving its diet of bugs and the bug’s diet of plants.
Now for the complexity. San Diego’s best known, worst invader is the Argentine ant. Homicidal foragers, these ants have colonized the Southwest — not only goose-stepping through our kitchens like North Koreans but cannibalizing most ant species along their route. One scientist tells me that Point Loma these days is one giant Argentine ant colony. They have removed the coastal horned lizard’s food supply, the larger harvester ants. The lizard, which when threatened shoots streams of blood from its eyes, is dwindling fast. But it’s not yet listed as threatened. Call its slow vanishing collateral species damage.
At the University of San Diego, Geoffrey Morse describes how Argentine ants push out aphids and scale insects, which attach themselves to plants for life. The Argentine land grab ruins things for other herbivores, bugs that feed on plants but don’t attach. “These ants scare off other insects,” he says, “as well as potential pollinators,” by stealing the nectar of flowers from the bees. To date, no predator can check the Argentine, though insecticides do. The problem there: such sprays end up killing every arthropod — more collateral damage.
Tracy Ellis, an entomologist with the county’s department of agriculture, weights and measures, tells me that every 60 to 90 days, a new foreign bug disrupts the $1.3 billion local horticulture industry. The most worrisome arrivals are fruit flies — followed by the Varroa mite (a slayer of bee pupa), the goldspotted oak borer (a killer of trees), and the red imported fire ant (venomous to humans). Ellis and her team punch back with inspections, quarantines, and sprays. She says the more invasive plants we have, the more they act as hosts for nonnative bugs. The hunt for, and eradication of, invasive pests is a huge undertaking in an agricultural state such as ours. Border communities can become stepping stones, spreading voluminous pest populations to the citrus orchards of Southern California and the vegetable kingdom of the Central Valley.
Above the San Pasqual Valley, from an overlook worthy of the California Impressionists, lies John Burr’s 30 acres of avocado groves. From behind his office’s leather-trimmed desk, Burr both lauds and worries over the avocado tree. Originally from Michoacán, Mexico, the trees find halcyon conditions southeast of Escondido. “They like water,” he tells me, “but they don’t like wet feet.” Well-drained soil, cool temperatures on average (though the valley is warming year over year), an ample growing season (slow and sunny), and low-volume sprinklers (not cheap) make for some happy Hass.
Until the 1990s, these groves knew no pests. Then, boom, from Mexican wood imports, came the persea mite, which gorges on the leaves’ chlorophyll. And from Vietnamese furniture, thrip, which feeds on the baby avocado and silvers the skin of the ripening fruit, a blemish, devaluing its worth. Burr says that “unchecked, the persea mite alone would have defoliated the grove.”
Suddenly, tree and crop are besieged, the insect dynamic is realigned, and growers rush in savvy entomologists (the UC Riverside docs are the most renowned) who bullseye the little buggers. Burr employs helicopter pilots to nape the groves with a “miticide of very low mammalian toxicity.” He also encourages a native (though beleaguered) mite, the Eusebius, to ramp up its predation of the invasives, mite against mite.
During the last drought, another pest arrived — the shot-hole borer, a wood-reaming Pacific Islander beetle. It nearly eradicated the willows in the Tijuana Valley, though the trees have come back. Heading north, the peripatetic borer found the avocado. Into the trunk it drills and packs a fungus as food for its young. Enough fungus plugs up the water-conductive tissues of the trees, and they die. Injecting pesticides into their congregations is the most reliable management tool.
Avocado as well as almond and citrus growers are learning how to apply and regulate a new, industry-wide “predacious complex,” a realignment of our local bug symbiosis. In the rancho days, these bad bugs did not exist. Not until sellers accustomed consumers to a predacious complex of their own — an import-export marketplace for avocados in which year-round availability of the fruit comes with the price of their carpetbagging pests.
The entomological and environmental communities can only approximate which and how many arthropods live among us, and this largely via anecdotal evidence. The move from anecdotal to hard science, however, is snowballing.
One of President Obama’s climate initiatives, working with the Department of Defense, has been to measure the flora and fauna of America’s public lands and to learn how deep the climate crisis actually is. It surprises people that the Department of Defense is the leader in protecting endangered species. But where better than on military bases? Despite combat training, soldiers have a relatively small footprint on federal land. Hundreds of thousands of acres of California, held by the government for generations, mostly post-World War II, retain swaths of native richness.
Which is why I’m with a civilian employee, Jim Asmus, a wildlife biologist with Environmental Security at the Marine Corps Base, Camp Pendleton. Asmus and the San Diego Natural History Museum are finishing a five-year baseline study, measuring species abundance and diversity in five vegetation communities. One project is to map coastal sage scrubland as insect habitats.
We’re about a half-mile east of I-5, on Stuart Mesa. To the east we see some of the base infrastructure — the commissary and the cheap-gas station — as well as the Santa Margarita river and salt flats, which, when wet, stir with brine shrimp. To the west lies the Pacific Ocean, whose shoreline sand dunes comprise local nesting grounds for the federally endangered California least tern and the threatened Western snowy plover, both insect gorgers. The bird whose turf we’re standing in is the California coastal gnatcatcher, another threatened species.
Asmus’s acumen beggars belief. He identifies most species we encounter by their Latin binomials. To capture insects, he sets out a charm of bee bowls, dayglo cups that visually lure flying bugs into soapy water; he disperses three-by-five “ant cards” flecked with bits of granola; he digs a hole for a pitfall trap into which wanderers tumble; and he uses a net on a staff to “beat and sweep” bushes when he espies a lot of crawling or hovering activity. In a two-hour survey, the goal is to catch a passel, identify them at his desk, and accrue data that will be more than an approximate observation of the Camp’s habitats. From his and others’ work, future researchers can measure the ongoing presence, abundance, and decline of one robust corner of San Diego arthropods.
He can’t say what’s in abundance or decline, though we do see the lilt and flit of honey bees and a few native bees, pollinators for the pumpkin patches in Carlsbad and other nearby squash. A female bee is collecting pollen from a coastal goldenbush. She will carry sacs of the high-protein material to her nest and make a bee bread in which she lays her eggs and in which the larvae incubate. As she flies from flower to flower, she pollinates, moving pollen from the male organ to the female organ of the plants. Asmus is an advocate for California native bees. He says that with the terrifying phenomenon of colony collapse disorder, it may be that solitary-dwelling native bees will, as food-crop pollinators, get the job done. “What hasn’t occurred is a measurable decline in the yield of crops. Part of the explanation has to be that native bees are picking up the slack.”
The point of the Pendleton survey is to baseline insect diversity and populations. Within a generation, we should know who’s surviving which climate stressors, and who’s not, as well as to what degree and why. Just in the scrubland of this Marine Corps base, 120 species of spiders have been found. That doesn’t mean their numbers are large. But at least they’re present.
Putting it another way, Asmus says: “Marine Corps training is compatible with natural resource and endangered species management.” Besides serving as a combat training site, Camp Pendleton has a new identity as a “nature reserve.”
Later, I get a photo of the day’s catch: “a black spider wasp, an unidentified orange wasp, two Lasioglossum bees in the lower left, and a small bee fly in the upper right.” The tiny sample reveals some species richness, fairly good for a hot, dry day.