A ladybug for most seasons

 

It was a typical misty morning in Golden Gate Park when entomologist Kristen Vollrath spotted a fluffy white insect ambling about on a concrete barrier behind the California Academy of Sciences. She scooped up the unidentified insect and brought it down to the entomology department where it was given the nickname “popcorn” due to its puffed appearance.

At first we thought popcorn might be a mealybug, a plant pest belonging to the family Pseudoccocidae. But popcorn was no mealybug! By the end of the week, the fluffy little nubbin transformed into it’s adult form and revealed its true identity: a ladybird beetle related to the red and black-spotted “ladybugs” we commonly see in the garden.

But how were we fooled so easily? It turns out that Popcorn was a special species of ladybird beetle (Cryptolaemus montrouzieri), whose larvae masquerade as the mealybugs they prey on, a form of “aggressive mimicry” that allows them to get close to their prey before gobbling them up. Commonly known as mealybug destroyers, these humble yet murderous little beetles were brought to California from their native home in Australia for a very specific and heroic purpose: to save the citrus!

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“You’re welcome”. Mealybug destroyer (Cryptolaemus montrouzieri) adult

If you were a citrus grower in 1860’s California, you would have had a lot of bugs to contend with. And I do mean bugs! True bugs to be exact, the order of insects that have what entomologists call “piercing or sucking” mouthparts. Don’t laugh! These specialized mouthparts allow true bugs to pierce plant tissues with their tiny beak-like rostrum and suck up the juices. Aphids are a well-known true bug that, along with many other plant-feeding true bugs, can cause all sorts of garden mayhem, including foliage wilt, leaf drop, and the stunted growth or even death of the plant.

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Aphid feeding on a plant. See the pointy mouthparts?

In the late 1860’s the California citrus industry was facing an economic crisis brought about, not by aphids, but by an invasive species of true bug from Australia, the cottony cushion scale (Icerya purchasi). Insecticides had little effect on these puffballs, and growers, at their wits end, resorted to pulling up infested trees and burning them.

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“But I’m just a lil’ poof”

Luckily there were a couple entomologists around to save the day! Albert Koebele, under the appointment of noted federal entomologist Charles Valentine Riley, had recently been transferred from his position in Washington D.C. to Alameda, California where he was studying insecticide effectiveness as well as local insect pests. He soon set his sights on fighting the cottony cushion scale scourge.

Curiously, citrus trees in Australia were largely unaffected by the cottony cushion scale even though the insect was native to the region. Riley noted this and reasoned that there must be natural predators of the cottony cushion scale in Australia that kept their numbers at a reasonable level.

And so in 1888 Riley sent Koebele on a mission to Australia to investigate potential cottony cushion scale predators that could be brought back to California. In addition to a species of parasitic fly, Koebele returned with a species of ladybird beetle called the vedalia beetle (Rodolia cardinalis).

Vedalia beetle

“My appetite will save the day!” Vedalia beetle (Rodolia cardinalis)

Koebele initially released the vedalia beetles on a tented orange tree infested with cottony cushion scale insects. In a few months the beetles had multiplied prolifically and devoured their prey. When the tent was opened the beetles spread to nearby trees and soon the entire orchard was free of the cottony cushion scale! As word of the amazing results spread, citrus growers from throughout the state came to gather the vedalia beetles and release them into their orchards. They spread rapidly and by 1890 California was almost entirely free of the cottony cushion scale and all of it’s gosh-darned cottony-ness.

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Happy orange tree

This idea – using nature to fight nature – is known as biological control or biocontrol, and this instance is regarded as the first successful implementation of it in the world. It can be very tricky, and, as usual, The Simpsons provides the best illustration of poorly thought out biocontrol.

In this case, however, Koebele used his entomologist know-how to implement a truly elegant solution and was seen as a local hero for growers in the state.

But his work was not over.

Several years after the cottony cushion scale had established itself in California, the citrus mealybug (Planococcus citri), another species of true bug with a deceptively cute name, was accidentally introduced from Asia around the world where it made itself quite the agricultural pest.

Mealybugs (family Pseudoccocidae), sometimes known as scale insects, are wingless as juveniles, have soft exoskeletons, and are coated in a waxy layer of protection that gives them their popcorn or puffed rice-like appearance. Males eventually change as they age, growing wings and losing their ability to feed and looking somewhat like gnats, whereas adult females retain their juvenile appearance and attach themselves to the plant where they secrete a powdery wax layer used for protection while they suck the plant juices. The female deposits masses of eggs on plants. The masses, known as ovisacs, are covered in fluffy, cottony layers of wax filaments. Juveniles feed on plant sap, which further damages them.

Citrus mealybug

Citrus Mealybug (larva or adult female)

Although citrus mealybugs attack a wide range of crops as well as wild and ornamental plants, the damage they do to citrus, like causing oranges to become lumpy and discolored and possibly fall off the tree, was a nightmare for growers in California. In 1891, they pressured Riley to send Koebele back to Australia to gather more predators that could combat the growing number of mealybugs. He ended up bringing back another species of ladybird beetle, except this one was a truly cunning beast. It came to be known as THE MEALYBUG DESTROYER…aka our little popcorn!

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mealybug destroyer munchies

The mealybug destroyer (Cryptolaemus montrouzieri), like the name implies, have a voracious appetite for mealybugs. To aid them in this venture, they employ a treacherous trick, which scientist’s refer to as “aggressive mimicry.” As juveniles, mealybug destroyers look very similar to mealybugs, a real-life case of a “wolf in sheep’s clothing” that allows them to get close to their prey while appearing harmless.

Cryptolaemus montrouzieri larva

Mealybug destroyer Larva

Adult mealybug destroyers are predominantly brown and have no spots, unlike many of the often brightly-colored ladybird beetles (Family Coccinellidae). Female mealybug destroyers lay their eggs among the cottony egg-sack of adult female mealybugs. The larvae, whose waxy coating makes them superficially resemble mealybugs, feed on mealybug eggs and larvae. It takes almost another month for the beetles to go through their pupal stage and become adults, at which point they continue eating mealybugs as well as laying hundreds of eggs among mealybug larvae for the rest of their 2-month lifespan.

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A (very accurate) depiction of a juvenile mealybug destroyer sneaking up on it’s prey. Cartoon by Rachel Diaz-Bastin.

As hoped, the mealybug destroyers devastated the citrus mealybug populations in citrus groves. But sadly these little chaps from down under got too chilly anytime it dipped much below 50 degrees ferenheit and (just like Springfield’s ill-fated gorillas), were unable to survive the winter in most areas. As a result, techniques for mass-rearing the beetle were developed for its release into groves where they could do their job during the warmer months.

In the Midwest, the mealybug destroyer is actually still used to protect ornamental plants from various species of mealybugs in greenhouses, where they stay nice and toasty year-round. They are also used for pest control in the warm wonderland at the San Francisco Conservatory of flowers in Golden Gate Park.

But, just like Kristen, you can sometimes find them out and about in coastal areas like San Francisco, where the fog provides a blanket that allows them to live much longer and fight their tiny battles in the wild, far away from their native homeland.

 

 

Thank you to Flickr creative commons folks for allowing the use of your wonderful images!:

https://www.flickr.com/photos/treegrow/

https://www.flickr.com/photos/35142635@N05/

 

 

 

 

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Tigers in the Night

Like a psychedelic flutter of love, a unicorn picnic, or a traveling band of kitten actors, butterflies spread happiness wherever they go. But as far as insects in the order Lepidoptera go, butterflies are just the tip of a very big iceberg. And perhaps – dare I say it – what’s hidden underneath is even more amazing.

Lepidoperans – also known as butterflies and moths – are an extremely large and diverse group of insects, with nearly 180,000 described species. “Lepis” means “scale” in latin, and “pteron” means “wing”. At the microscopic level, it’s easy to see how they got those fancy names:

Boloria (Clossiana) euphrosyne

Pearl-bordered fritillary butterfly (Boloria euphrosyne), wing close-up. (Photo by Gilles San Martin)

Those scaley-looking things on this butterfly wing are, in fact, scales! More accurately, they are modified hairs, but we call them scales anyway, and lepidopterans are covered in them. These tiny structures overlap slightly like shingles on a very colorful house, and are what give butterflies and moths their diversity of colors and patterns.

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Sunset Moth (Chrysiridia rhipheus), wing scales. (Photo by Macroscopic Solutions)

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Sunset Moth (Chrysiridia rhipheus), wing scales. (Photo by Macroscopic Solutions)

Many of these colors and patterns are familiar – like the striking orange and black of a monarch, or the iridescent blue of a morpho butterfly lilting through the rainforest. They are familiar because, for the most part, butterflies are up and about when we are.

Although some moths are active during the daytime, the majority of moths are hidden from our normal waking life. But wait until the twillight, or until the stars come out. Check your porch light, or better yet, grab a white sheet, a lamp, and a beer, and you can see the myriad moths that make up the underside of the Lepidoptera iceberg.

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Mangina argus, subfamily Arctiinae, Nepal. (Photo by Rachel Diaz-Bastin)

Mangina argus, from Southeast Asia, is a particularly lovely member of the nightime set. This species has two noteworthy distinctions: 1) It may possibly have the funniest genus name ever. And 2) It has striking pink and silver markings reminiscent of a butterfly. Except that it isn’t. It’s a moth.

Moths make up roughly 80% of all known Lepidoptera (that’s almost 160,000 known species, compared to roughly 17,500 butterflies). Most of them are cryptic, but some of them are colorful. The beauty of moths lies in their incredible diversity. Don’t try to pin them down! (Unless you are starting a moth collection of course…)

Utethesia bella

Utethesia bella, subfamily Arctiinae, Florida. (Photo by Rachel Diaz-Bastin)

There are more species of moth in the United States than birds in the entire world, and more moths in Texas alone than there are species of mammal in the entire world. Take that, pandas!
In terms of charisma, the pandas of the moth world might be those in the subfamily Arctiinae, commonly known as tiger moths. They are an incredibly diverse group, with 11,000 species found all over the world. Like the beautiful day-flying Bella moth pictured above, their playful, often beautifully geometric patterns seem like something out of a surrealist’s dreamworld. Or a Joan Miro painting.
Chionaema spp.

Chionaema sp., subfamily Arctiinae, Assam. (Photo by Rachel Diaz-Bastin)

Chionaema perornata

Chionaema perornata, subfamily Arctiinae, Assam. (Photo by Rachel Diaz-Bastin)

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Chionaema sp., subfamily Arctiinae, Assam. (Photo by Rachel Diaz-Bastin)

For potential predators, however, tiger moths look less like a dreamy painting, and more like an unwise snack. Their bright, bold colors – otherwise known as aposematic coloration – advertise that their bodies are infused with poisonous chemicals, such as cardiac glycosides and pyrrolizidine alkaloids, aquired from plants in their environment.
Like other creatures with warning coloration, such as poison dart frogs, coral snakes, Niki Manaj, and flamboyant cuttlefish, tiger moths have a certain dangerous beauty.
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Halysidota masoni, subfamily Arctiinae, Cuernavaca, Mexico. (Photo by Rachel Diaz-Bastin)

Automolis harteri

Automolis harteri, subfamily Arctiinae, Brazil. (Photo by Rachel Diaz-Bastin)

A particularly lovely species is Anaxita decorata. Commonly known as the decorated beauty, it graces Central American evenings like a flying sunset, with bold silver stripes in a wash of vermillion and gold.
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Anaxita decorata, subfamily Arctiinae, Oaxaca, Mexico. (Photo by Rachel Diaz-Bastin)

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Anaxita decorata, subfamily Arctiinae, Oaxaca, Mexico. (Photo by Rachel Diaz-Bastin)

The bright warning colors of tiger moths may serve as protection from daytime predators. But what happens when the lights go out? And bats get the munchies?

Automolis critheis, subfamily Arctiinae, Panama.

Automolis critheis, subfamily Arctiinae, Panama. (Photo by Rachel Diaz-Bastin)

Well, many species of tiger moth have found a way to warn predators at night too – not with sight – but with sound. These species can produce ultrasonic clicks that warn approaching bats that they are distasteful. One species (that is actually tasty), Bertholdia trigona, can produce clicks at such a high rate (up to 4,500 per second), that that it can even jam bat echolocation, resulting in up to tenfold decrease in bat capture efficiency.
Haploa clymene

Haploa clymene, subfamily Arctiinae, Virginia. (Photo by Rachel Diaz-Bastin)

Haploa contigua

Haploa contigua, subfamily Arctiinae, Wisconsin. (Photo by Rachel Diaz-Bastin)

Whether vibrant like tiger moths or so cryptic they blend into the trees, moths truly are among the most intriguing insects. If you want to explore the hidden netherworld of moths for yourself, you are in luck! They are super easy to observe. All you need to do is go outside at dusk or later and set out a white sheet and a light, then sit back and shout, “come to me my moth-y friends muahahahahaha!” Learning to identify them is fascinating, and with National Moth Week coming up in July (yes you read that right, National Moth Week!), anyone can join in the fun.

Halysidota intensa

Halysidota intensa, subfamily Arctiinae, Peru. (Photo by Rachel Diaz-Bastin)