Tag Archives: nature

The Scaly Crickets

by Joseph DeSisto

Among many new species named today, some of the most unusual were three new crickets from Southeast Asia (Tan et al. 2015). These crickets belong to the obscure and poorly-known family Mogoplistidae, cousins to the more recognizable (and audible) field crickets (Gryllidae). They look like field crickets too, except that their bodies are covered in scales.

A scaly cricket (Arachnocephalus vestitus). © Entomart.

A scaly cricket (Arachnocephalus vestitus). © Entomart.

When you touch a butterfly’s wings, you might notice a fine, powdery substance rubbing off on your fingers. The powder is made up of microscopic scales, which cover the wings of butterflies and moths. Scales give the wings their color, but they also provide insulation and protect the wings during flight. Perhaps most importantly, scales can fall off and make the wings slippery. This allows butterflies and moths to evade a careless hand as easily as a wet bar of soap.

The scientific name for butterflies and moths is Lepidoptera, which translates to “scaly wing” — scales are one of the most important features defining the group. However, many other groups of insects also have scales. Mosquitoes and silverfish have them, and so do scaly crickets.

The scales of a scaly cricket (Ornebius formosanus). Figure from Yang and Yen (2001), licensed under CC BY 2.0.

The scales of a scaly cricket (Ornebius formosanus). Figure from Yang and Yen (2001), licensed under CC BY 2.0.

Cricket scales, like those of butterflies and mosquitoes, are microscopic, powder-like, and easily shed. To really appreciate their beauty, a scanning electron microscope is needed. The first look came in 2001, when Yang and Yen published the first high-resolution images of cricket scales.

Aside from being scaly, scaly crickets aren’t all that unusual. They are adaptable, able to eat decaying plants as well as other insects, and they tend to live in moist sandy habitats. No scaly crickets are capable of flight, and females lack wings entirely, but the males do have small wings which they rub together to make chirping sounds (Love and Walker 1979). Click on the audio file below to listen to an amorous male scaly cricket (recorded by Thomas J. Walker).

Of the three new species, two were found in the Sakaerat Biosphere Reserve, in Thailand. This reserve consists mainly of high-altitude dry forest, with a few grasslands, and is home to many endangered species including tigers and giant black squirrels.

The third cricket is native to Pulau Ubin, an island off the coast of Singapore. Pulau Ubin is one of the last remaining wild areas in the already tiny country. Singapore’s government has been eager to develop portions of the island, but in recent years tourism has become more profitable. Fear of losing foreign visitors has encouraged officials to protect, rather than level, valuable habitat. For now, the status of the new scaly crickets appears secure, but in rapidly urbanizing Southeast Asia, nothing is certain.

A scaly cricket (Mogoplistes brunneus). © Entomart.

A scaly cricket (Mogoplistes brunneus). © Entomart.

Cited:

Love R.E. and T.J. Walker. 1979. Systematics and acoustic behavior of scaly crickets (Orthoptera: Gryllidae: Mogoplistinae) of eastern United States. Transactions of the American Entomological Society 105:

Tan M.K., P. Dawwrueng, and T. Artchawakom. 2015. Contribution to the taxonomy of scaly crickets (Orthoptera: Mogoplistidae: Mogoplistinae). Zootaxa 4032(4): 381-394.

Yang J. and F. Yen. 2001. Morphology and character evaluation of scales in scaly crickets (Orthoptera: Grylloidea: Mogoplistidae). Zoological Studies 40(3): 247-253.

Advertisements

Two New Species of Ant-Decapitating Fly

by Joseph DeSisto

An ant-decapitating fly. Photo by Scott Bauer, in public domain.

An ant-decapitating fly. Photo by Scott Bauer, in public domain.

Today saw the description of two new species of South American flies, both fire ant parasites that decapitate their victims. The two new species were discovered in Brazil and Argentina, associated with fire ant mounds in their native territory (Plowes et al. 2015).

Ant-decapitating flies, as might be expected, have unusual and macabre life histories. The adults are tiny, just a few millimeters in length, with the general appearance of fruit flies. Instead of hovering around rotten bananas, however, female ant-decapitating flies hang around ant mounds. When the time is right, a fly soars down to meet her victim, using a hooked, needle-like ovipositor to inject an egg into the ant’s head (Porter 1998).

With egg laid, her work is done. The fly departs, ant still intact and seemingly healthy.

A fly attacking a fire ant, hoping to lay its egg on the ant's head. Photo by Sanford Porter, in public domain.

A fly attacking a fire ant, hoping to lay its egg on the ant’s head. Photo by Sanford Porter, in public domain.

Not all is well, however. From the fly’s egg emerges a maggot that, as it grows, eats away at the inside of the ant’s head. At the same time, the maggot secretes chemicals that cause the ant to go mad, fleeing its colony and finding shelter in moist leaf litter. With its host almost spent, the maggot severs the ant’s head, and forms a cocoon or pupa inside the now-hollow shell. Some weeks later, a new fly emerges and takes off in search of a new ant for her offspring.

This all sounds very sinister, but it also could be very useful to humans. As it happens, many of these flies specialize in decapitating fire ants and, in enough numbers, can seriously impact fire ant colonies. Now that invasive fire ants are well-established in the southern U.S., the Department of Agriculture is looking to ant-decapitating flies to control the ants’ march north.

The remains of a fly's victim. Photo by Sanford Porter, in public domain.

The remains of a fly’s victim. Photo by Sanford Porter, in public domain.

Whether the two new species of ant-decapitating fly will be useful in controlling fire ants remains to be seen. Multiple fly species have already been introduced in states like Texas (Gilbert and Patrock 2002) and Alabama (Porter et al. 2011), where fire ants are a serious problem for agriculture and human health. In these states the flies have become established and already have a tangible impact on fire ant populations.

However, not all species fare equally well. In order to be useful in controlling fire ants, the flies must be able to adapt to the southern U.S. climate, as well as all the new predators they may not have faced in South America.

Plowes and colleagues (2015) suggest that many more unknown species of ant-decapitators live in remote regions of South America. Discovering new species may help scientists figure out which flies will be most successful at colonizing the U.S., and which species will have the biggest impact on fire ant populations.

Cited:

Gilbert L.E. and R.J.W. Patrock. 2002. Phorid flies for the biological suppression of imported fire ant in Texas: region specific challenges, recent advances and future prospects. Southwestern Entomologist Supplement 25: 7-17.

Plowes R.M., P.J. Folgarait, and L.E. Gilbert. 2015. Pseudacteon notocaudatus and Pseudacteon obtusitus (Diptera: Phoridae), two new species of fire ant parasitoids from South America. Zootaxa 4032(2): 215-220.

Porter S.D., L.F. Graham, S.J. Johnson, L.G. Thead, and J.A. Briano. 2011. The large decapitating fly Pseudacteon litoralis (Diptera: Phoridae): successfully established on fire ant populations in Alabama. Florida Entomologist 94(2): 208-213.

Porter S. D. 1998. Biology and behavior of Pseudacteon decapitating flies (Diptera: Phoridae) that parasitize Solenopsis fire ants (Hymenoptera: Formicidae). Florida Entomologist 81(3): 292-309.

Poisonous Frogs, Beetles, and Birds

by Joseph DeSisto

Meet the golden poison frog of Colombia’s coastal rain forests. This frog, one of nearly 200 species of poison frogs, is by far the most toxic. A single frog packs enough poison to kill 10,000 mice, or 10 or more humans (Myers et al. 1978).

The golden poison frog (Phyllobates terribilis). Photo by Brian Gratwicke, licensed under CC BY 2.0.

The golden poison frog (Phyllobates terribilis). Photo by Brian Gratwicke, licensed under CC BY 2.0.

For the golden poison frog and its close relatives in the genus Phyllobates, batrachotoxin is the weapon of choice. Batrachotoxin acts on the nervous system, opening up the membranes of nerve cells so they can no longer carry signals to and from the brain. Death comes from paralysis, which leads to heart failure.

The golden poison frog was only discovered in 1971 when scientists found them around an indigenous Colombian (Emberá Chocó) village (Myers et al. 1978). The Emberá use the frogs to lace poison darts, with which they hunt game in the surrounding forest. The frog-handlers were careful to cover their hands with leaves, with good reason. Scientists who touched the frog felt a strong burning sensation, and they stressed in their initial description that:

The new species is potentially dangerous to handle: One freshly caught frog may contain up to 1900 micrograms (µg) of toxins, only a fraction of which would be lethal to man if enough skin secretion came into contact with an open wound.”(Myers et al. 1978, pp. 311)

The black-legged poison frog (Phyllobates bicolor), closely related to terribilis but not quite as toxic. Photo by Drriss and Marrionn, licensed under CC BY-NC-SA 2.0.

The black-legged poison frog (Phyllobates bicolor), closely related to terribilis but not quite as toxic. Photo by Drriss and Marrionn, licensed under CC BY-NC-SA 2.0.

It is important, as the frog’s discoverers remind us, “to be cautionary, not alarmist” (Myers et al. 1978, pp. 340). Even though in theory these frogs are dangerous, there is no record of a person ever being killed by one. Although the poison can go through a person’s skin, it seldom does so in enough quantity to injure. The frogs do not bite. So if you see golden poison frogs while exploring in Colombia, do not panic, but be wary. However delicious and lemon-drop-colored they may seem, definitely don’t try eat them.

Golden poison frogs are sometimes sold in the pet trade, since they lose their poison after being taken out of the wild. This is probably because frogs get batrachotoxin from their food: soft-winged beetles that make the toxin themselves (Dumbacher et al. 2004). In captivity, frog-keepers give their pets a blander diet of crickets and fruit flies, which don’t contain batrachotoxin.

An example of a soft-winged beetle, in the same family as those eaten by poison frogs. Photo by Udo Schmidt, licensed under CC BY-SA 2.0.

An example of a soft-winged beetle, not the same species, but in the same family as those eaten by poison frogs. Photo by Udo Schmidt, licensed under CC BY-SA 2.0.

Soft-winged beetles are found all over the world, especially in the tropics, but so far only a few other animals are known to eat them and use their batrachotoxins. Three of these are poison frogs, all found in a small rain forest region of Colombia. The others are birds. Yes, there are poisonous birds, and even though this blog is explicitly not about birds or mammals, I’m going to break that rule today.

The hooded pitohui (Pitohui dichrous) -- both males and females are brightly colored. Photo by Katerina Tvardikova, licensed under CC BY-NC-SA 3.0.

The hooded pitohui (Pitohui dichrous) — both males and females are brightly colored. Photo by Katerina Tvardikova, licensed under CC BY-NC-SA 3.0.

The toxic birds are all found in New Guinean rain forests, and most belong to a group of insect-eaters called pitohius (pronounced PI-to-hooies). Pitohui birds are related to the orioles and blackbirds found in more temperate climes. Shown above is the hooded pitohui, first found to be poisonous when a bird researcher handled one and left with a tingling, burning sensation in his hand.

Later study showed that the hooded pitohui, along with two other related species, has feathers laced with batrachotoxins (Dumbacher et al. 1992). More than a decade later, the same scientists demonstrated that toxin-wielding pitohui birds eat soft-winged beetles, and that these same beetles are loaded with batrachotoxin (Dumbacher et al. 2004). Despite being toxic, the birds are not nearly as dangerous as golden poison frogs, and there is little risk to a careful handler.

The variable pitohui (Pitohui kirhocephalus), not as showy as its cousin, but toxic all the same. Photo by Katerina Tvardikova, licensed under CC BY-NC-SA 3.0.

The variable pitohui (Pitohui kirhocephalus), not as showy as its hooded cousin, but toxic all the same. Photo by Katerina Tvardikova, licensed under CC BY-NC-SA 3.0.

Several more birds are now known to use batrachotoxins, and all are found in New Guinea (Weldon 2000). Many of them have similar red-and-black color patterns. By having similar colors, multiple bird species can work together to “educate” predators who might not be aware of the poisonous feathers (Dumbacher and Fleischer 2001). To make matters even more interesting, the toxins in bird feathers apparently serve as a repellent to parasitic lice (Dumbacher 1999).

We may continue to learn more about these amazing birds and their lives, or we may not. Most of these birds are becoming rarer and rarer as New Guinean rain forest is slashed and burnt, tilled and grazed into nothing.

I’ve written several articles about poisons and venoms: click here to learn about brown recluse venom and here to learn about tetrodotoxin, a poison used by many fish as well as newts, snails, and blue-ringed octopuses.

Darren Naish, writer of the superb science blog Tetrapod Zoology, writes often about birds. Click here for one of his articles on a poisonous New Guinean species. Note that the article is not on his most recent blog site, which is updated regularly at the first link to Scientific American.

To learn more about the relationship between lice and toxic pitohui birds, click here to read an excellent article by Bianca Boss-Bishop on the aptly-named blog Parasite of the Day.

Cited:

Dumbacher J.P. 1999. Evolution of toxicity in Pitohuis: I. effects of homobatrachotoxin on chewing lice (order: Phthiraptera). The Auk, 116: 957-963.

Dumbacher J.P., A. Wako, S.R. Derrickson, A. Samuelson, and T.F. Spande. 2004. Melyrid beetles (Choresine): a putative source for the Batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proceedings of the National Academy of Sciences U.S.A. 101(45): 15857-15860.

Dumbacher J. P., B.M. Beehler, T. F. Spande, H. M. Garra¡o, and J.W. Daly. 1992. Homobatrachotoxin in the genus Pitohui: chemical defense in birds? Science 258: 799-801.

Dumbacher J.P. and R.C. Fleischer. 2001. Phylogenetic evidence for colour pattern convergence in toxic pitohuis: Müllerian mimicry in birds? Proceedings of the Royal Society of London B 268(1480): 1971-1976.

Myers C.W., J.W. Daly, and B. Malkin. 1978. A dangerously toxic new frog (Phyllobates) used by Emberá Indians of western Colombia, with a discussion of blowgun fabrication and dart poisoning. Bulletin of the American Museum of Natural History 161(2): 311-365.

Weldon P.J. 2000. Avian chemical defense: toxic birds not of a feather. Proceedings of the National Academy of Sciences U.S.A. 97(24): 12948-12949.

Are Tarantulas Dangerous? Most Aren’t, A Few Might Be

Of the 900 or so known tarantula species, almost all are harmless (Isbister et al. 2003, Lucas et al. 1994). A bite by any large spider can be painful even if no venom is injected, since the fangs themselves are essentially big needles. Even if venom is injected, however, most tarantula bites result in little more than local pain and swelling. When there are medical problems, the cause is usually shock or an allergic reaction, rather than the action of the venom itself.

The Chilean rosehair tarantula (Grammostola rosea), a hardy and docile pet. Photo from Insects Unlocked, in public domain.

The Chilean rosehair tarantula (Grammostola rosea), a hardy and docile pet. Photo from Insects Unlocked, in public domain.

That said, not all tarantulas are equally venomous. The most common tarantulas sold in pet shops are all pretty benign: the Chilean rose hair, the Mexican redknee, and the pinktoe tarantulas have both mild venom and docile habits. They can be handled gently with almost no risk of being bitten.

Other, more exotic species kept by seasoned tarantula experts include the cobalt blue, the goliath birdeater, and the golden starburst tarantulas. These are beautiful and impressive captives — the goliath birdeater can attain a 12-inch leg span. The cobalt blue and golden starburst are stunningly colorful animals, the latter approximately matching the color of Donald Trump’s hair. These species are also more nervous and willing to bite, and their bites are generally more painful (e.g., Takaoka et al. 2001).

The golden starburst tarantula (Pterinochilus murinus), guarding its silken retreat. Photo by Stefan Walkowski, licensed under CC BY-SA 3.0.

A golden starburst tarantula (Pterinochilus murinus) guarding its silken retreat. Photo by Stefan Walkowski, licensed under CC BY-SA 3.0.

Avid tarantula enthusiasts don’t get most of their spiders from pet shops. Instead they buy tarantulas from other spider-keepers who breed their pets, or from companies that import spiders and other animals from around the world. With international trade, hundreds of species are available for hobbyists collect. Many of these are poorly known, most have not had their venom studied, and a few haven’t even been formally described by scientists.

Where venomous animals are concerned, gaps in scientific knowledge can have serious consequences. A few years ago a Swiss man was bitten by one of his many pet tarantulas — at first, the only symptoms were mild pain, hot flushes and sweating. He brought himself to the hospital 15 hours later, when he began to experience severe muscle cramps and stabbing chest pain. Doctors gave him medication (midazolam and lorazepam) that reduced the symptoms, but muscle cramps did not disappear completely until three weeks after the bite (Fuchs et al. 2014). The tarantula in this case was a regal ornamental tarantula, a magnificent tree-dwelling spider native to India.

A regal ornamental tarantula (Poecilotheria regalis). Photo by Morkelsker, in public domain.

A regal ornamental tarantula (Poecilotheria regalis), with a leg span up to 6 inches. Photo by Morkelsker, in public domain.

There are at least 16 species of ornamental tarantulas, all from tropical forests in India and Sri Lanka. Most of them can be found in the exotic pet trade, and many have become popular with tarantula keepers looking for something a little more exciting. Exciting is certainly what they get: ornamental tarantulas are stunningly beautiful, as well as extremely fast and agile climbers. They are also quick to bite if cornered. Ornamental tarantula venom, while not deadly, is certainly underestimated.

To see if muscle cramps and chest pain were common symptoms of ornamental tarantula bites, Joan Fuchs and colleagues (2014) looked at 26 case reports, most of which were blog entries by seasoned tarantula keepers and breeders. Of the cases, 58% involved muscle cramps, along with other symptoms such as fever and heavy breathing. A few patients even lost consciousness for short periods. All bites were painful, but those that led to muscle cramps were severely so. This led the researchers to believe that, in cases where muscle cramps did not appear, the spider had simply injected much less venom.

The metallic ornamental tarantula (Poecilotheria metallica). Photo by Søren Rafn, licensed under CC BY-SA 3.0.

The metallic ornamental tarantula (Poecilotheria metallica). Photo by Søren Rafn, licensed under CC BY-SA 3.0.

It’s worth remembering that no tarantula bite has ever been fatal. It is a sorry fact, however, that by far the greatest source of knowledge on tarantula bites comes not from scientists, but from spider-keepers who take great pains (literally) to record their symptoms after every bite. This information is shared with other spider-keepers online at websites like Arachnoboards, so other hobbyists know what to expect from each species.

Such informal reports have been done for many species that have yet to be studied closely by scientists, and some that haven’t even been “discovered” (i.e., been given Latin names and formally described). The scientific axiom that “more work is needed” may be a cliché, but regarding tarantula bites and spider venom in general, it is certainly true.

Cited:

Fuchs J., M. von Dechend, R. Mordasini, A. Ceschi, and W. Nentwig. 2014. A verified spider bite and a review of the literature confirm Indian ornamental tree spiders (Poecilotheria species) as underestimated theraphosids of medical importance. Toxicon 77: 73-77.

Isbister G.K., J.E. Seymour, M.R. Gray, and R.J. Raven. 2003. Bites by spiders of the family Theraphosidae in humans and canines. Toxicon 41(4): 519-524.

Lucas S.M., P.I. Da Silva Júnior, R. Bertani, and J.L. Cardoso. 1994. Mygalomorph spider bites: a report on 91 cases in the state of São Paulo, Brazil. Toxicon 32(10): 1211-1215.

Takaoka M., S. Nakajima, H. Sakae, T. Nakamura, Y. Tohma, S. Shiono, and H. Tabuse. 2001. Tarantulas bite: two case reports of finger bites from Haplopelma lividum. The Japanese Journal of Toxicology 14(3): 247-250.

The Mountain King

by Joseph DeSisto

During my trip to Arizona, I saw tarantulas, scorpions, black widows, giant centipedes, lizards, and way too many insects to name here. What I didn’t see a lot of were snakes — in fact I only saw two, but those two snakes were the most beautiful I had ever seen.

The first was in Sierra Vista where, after a long day of beating bushes for caterpillars, we pulled into a driveway to find one of the most stunning animals on earth: the Arizona mountain kingsnake.

An Arizona mountain kingnake, held by Benedict Gagliardi. Photo by Joseph DeSisto.

An Arizona mountain kingnake, held by Benedict Gagliardi. Photo by Joseph DeSisto.

The Arizona mountain kingsnake (Lampropeltis pyromelana) and its cousin, the California mountain kingsnake (L. zonata), are some of the most sought-after snakes by North American reptile-lovers. Both are incredibly beautiful, but not especially common, and they prefer high-elevation habitats that aren’t always very accessible to naturalists. Mountain kingsnakes are secretive, spending most of their time underground. They seldom bask in the sun like garter snakes or rattlesnakes, instead emerging only to track hunt their lizard and rodent prey, which they kill by constriction.

The Arizona mountain kingsnake, from Sierra Vista. Photo by Joseph DeSisto.

The Arizona mountain kingsnake, from Sierra Vista. Photo by Joseph DeSisto.

The bright red and yellow bands are warning to predators. Snake-eating birds and mammals might easily confuse the kingsnake with the extremely venomous Sonoran coralsnake, which is also found in Arizona but prefers the lower-elevation desert scrub habitats, rather than the upland pine forests favored by the mountain kingsnake.

I am on a lucky streak when it comes to snakes. I don’t see very many, but the ones I do see are special enough to make my friends jealous. During a May trip to the Appalachians, I saw only five snakes, but two of those were corn snakes and two more were eastern worm snakes. Despite both of these being great finds, I left the South feeling a bit slighted, since what I really wanted to see was a venomous snake, a timber rattlesnake or copperhead. I had never seen a venomous snake in the wild before, so when I decided to go to Arizona, known for being rattlesnake country, I was ready.

The other mountain kingsnake, L. zonata from California. Photo by James Maughn, licensed under CC BY-NC 3.0.

The other mountain kingsnake, L. zonata from California. Photo by James Maughn, licensed under CC BY-NC 3.0.

We spent a few days in Sierra Vista collecting caterpillars and setting up lights at night to attract moths and other insect curiosities. Pat Sullivan, a beetle expert who lives in the area, had several pet rattlesnakes and was eager to show me a rock pile he had set up on his property as snake habitat.

The night he took me to the rock pile, just a few yellow scales caught the beam from my flashlight. I could see perhaps an inch of snake that looped out from under a rock, and I wanted to flip the rock to see more. I also, however, didn’t want to put my hands right next to a rattlesnake who might not be as sociable as I was. So I left the snake be, and returned to the light where moths and beetles kept me busy for the rest of the evening.

The last morning before we left Sierra Vista, I returned to the rock pile. After a few minutes of leaning over for a good angle, I realized the snake was in exactly the same position as before, only a few scales visible. In daylight those few scales were truly beautiful — they yellow and tan color revealed this was a black-tailed rattlesnake (Crotalus molossus), one of the prettiest rattlesnakes around. Pat got a long stick and, very carefully, flipped the rock over:

This is what I saw -- half a black-tailed rattlesnake. Photo by Joseph DeSisto.

Half a black-tailed rattlesnake. Photo by Joseph DeSisto.

The snake made no attempt to strike or even rattle. It simply slid beneath the rock pile with the grace of an animal that knows it can hurt you, and knows that you know it can hurt you. In the end I only had a few seconds to see less than half of a rattlesnake, but I’ll take it. I saw my first and, to date, only venomous snake in the wild, and it was one of the most beautiful creatures I’ve ever had the pleasure of meeting.

The Alligator’s Nest

by Joseph DeSisto

If you are careless in wandering along the swamps of the southeastern United States, you may hear this sound emanating from the brush:

[Recording by Adam Britton, used with permission.]

That is the hiss of an angry American alligator — if you hear it on land, you may have stumbled upon an alligator nest. If so, do not delay in your retreat. A mother alligator’s warning is no bluff.

An American alligator (Alligator mississippiensis) from South Carolina. Photo by Gareth Rasberry, licensed under CC BY-SA 3.0.

An American alligator (Alligator mississippiensis) from South Carolina. Photo by Gareth Rasberry, licensed under CC BY-SA 3.0.

If you could stay, however, you might be surprised at the tenderness with which alligators treat their offspring. When a female is ready to lay, she hauls herself on shore and finds a shaded, protected area not too far from the water. She lays her eggs in a pile of mud and leaf litter, then heaps more litter on top of them, so that the end result is a leaf-and-mud pile 2-3 feet tall and 5-7 feet wide (McIlhenny 1935).

A thick layer of insulating leaves also keeps the eggs at a more-or-less constant temperature. On a daily basis, even though the environment might go through wild changes in temperature, the inside of the nest stays within 3° F (Chabreck 1973). Alligator eggs usually take around 2 months to develop, and stable temperatures are critical.

Baby American alligators from the Okefenokee Swamp in Georgia. Photo by William Stamps Howard, licensed under CC BY-SA 3.0.

Baby American alligators from the Okefenokee Swamp in Georgia. Photo by William Stamps Howard, licensed under CC BY-SA 3.0.

In human beings, the presence or absence of a Y chromosome decides whether one develops into a male or female. In other words, human sex determination is chromosome-dependent. Alligators instead, like many reptiles, show temperature-dependent sex determination. Between days 20 and 35 of incubation, if eggs are kept between 86° and 93°F, a roughly even mixture of females and males will be the result (Ferguson and Joanen 1983). If, however, the batch stays above 93°, only males will emerge, and if below 86°, only females.

Alligator babies aren’t the only things that grow in alligator nests. The heap of dead leaves, twigs, and mud provides a haven for bacteria and other microorganisms. As bacteria digest the rotting vegetation, they produce heat — enough to keep the eggs 3-4° warmer than the habitat outside the nest (Chabreck 1973). In fact, bacteria keep alligator nests so consistently warm that the nests are also home to unique, heat-loving fungi (Tansey 1973).

More baby alligators! Photo by Ianaré Sévi, licensed under CC BY-SA 3.0.

More baby alligators! Photo by Ianaré Sévi, licensed under CC BY-SA 3.0.

Eggs, alligator or otherwise, look simple but are surprisingly complex. The “solid” shell is mostly made of calcium, but it’s far from a perfect seal — the whole surface is peppered with thousands of tiny holes, allowing the egg to take in oxygen and water, while “exhaling” carbon dioxide (Kern and Ferguson 1997). The thickness of the shell must be precise — too thin and the egg is easily crushed or infected by disease, but too thick and breathing, drinking, and hatching become difficult.

On alligator farms, where alligators are bred and raised for their skins, roughly 30-60% of eggs hatch successfully. Meanwhile more than 90% of alligator eggs hatch successfully in the wild (Kern and Ferguson 1997), as long as the nest isn’t flooded or raided by predators first. Experiments have shown that captive alligator eggs are less porous than their wild counterparts, and of the captive eggs, the least porous are doomed to die before hatching (Wink et al. 1990). Captive alligator eggs also have much thicker shells than wild eggs. So where is the difference coming from?

A baby American alligator. Photo by Ianaré Sévi, licensed under CC BY-SA 3.0.

A baby American alligator. Photo by Ianaré Sévi, licensed under CC BY-SA 3.0.

The bacteria in wild alligator nests, aside from producing heat, also produce acids. These acids aren’t strong or abundant enough to harm the developing reptiles, but over the 2 months it takes for them to develop, acids gradually erode the hard, calcium shell around each egg (Ferguson 1981). By the time the alligator is ready to hatch, its shell is significantly thinner than when the egg was first laid — just thin enough for the hatchling to easily break through.

[Recording by Adam Britton, used with permission.]

As they leave their eggs, baby alligators sound an alarm to their mother, who industriously digs them out of the nest where they spent the first two months of their lives. Although these months might seem uneventful, they are in fact full of challenges, which alligator eggs, however simple and unassuming, have ways to overcome.  Those hatchlings that survive face yet another gauntlet of obstacles, including predators and ruthless competition from their siblings. It’s tough being a baby alligator, and maybe even tougher being an egg, but the toughest few have a chance to become some of the most awe-inspiring top predators in North America.

Dr. Adam Britton, a crocodile researcher at the Charles Darwin University in Northern Territory, Australia, has graciously allowed me to use the audio files in this article. More files, along with a wealth of information about crocodilian biology and conservation, can be found at his website, crocodilian.com.

Cited:

Chabreck R.H. 1973. Temperature variation in nests of the American alligator. Herpetologica 29(1): 48-51.

Ferguson M.W.J. 1981. Increased porosity of the incubating alligator eggshell caused by extrinsic microbial degradation. Experientia 37(3): 252-255.

Ferguson M.W.J. and T. Joanen. 1983. Temperature-dependent sex determination in Alligator mississippiensis. Journal of Zoology 200(2): 143-177.

Kern M.D. and M.W.J. Ferguson. 1997. Gas permeability of American alligator eggs and its anatomical basis. Physiological Zoology 70(5): 530-546.

McIlhenny E.A. 1935. The Alligator’s Life History. Christopher Publishing House, Boston. 117 pp.

Tansey M.R. 1973. Isolation of thermophilic fungi from alligator nesting material. Mycologia 65(3): 594-601.

Wink C.S., R.M. Elsey, and M. Bouvier. 1990. Porosity of eggshells from wild and captive, pen-reared alligators (Alligator mississippiensis). Journal of Morphology 203(1): 35-39.

Life in Blackwater

by Joseph DeSisto

Just a few years before Darwin published his work on evolution by natural selection, his contemporary, Alfred Russel Wallace, finished a four-year-long tour of the Amazon Basin. During these travels he explored the Amazon River and its tributaries, met with indigenous tribes, and collected a shipload of biological specimens, which he planned to return to England to sell. Sadly the ship and all its contents, save a few notes and sketches, were lost in a fire at sea. From those notes was forged a book documenting Wallace’s travels and his observations on natural history in the Amazon (Wallace 1853).

When Wallace began to explore the Rio Negro or “Black River,” the Amazon’s largest tributary, he noticed that the water seemed darkly stained, like tea or coffee. Similar, smaller rivers could be found across the Amazon — such rivers were usually deep, slow-moving, and wound through forests or swamps. “Blackwater” (aside from being an episode of Game of Thrones) is the name Wallace (1853) used to describe these stained waterways. Where the blackwater of the Rio Negro meets the silt-laden, “whitewater” of the Amazon, the transition is sharp and visible from space.

The junction of the whitewater Amazon (left) and the blackwater Rio Negro (right) near Manaus, Brazil. Photo by Lecomte, licensed under CC BY-SA 3.0.

The junction of the whitewater Amazon (left) and the blackwater Rio Negro (right) near Manaus, Brazil. Photo by Lecomte, licensed under CC BY-SA 3.0.

Not only do blackwater rivers look like tea, they effectively are tea — the color comes from tannins, organic molecules that seep into the water as certain types of tannin-bearing plants die and decompose (Janzen 1974). Whether a river has blackwater or not depends entirely on the plant life growing at its banks. In life, certain plants use tannins as a protection against insects. In death, the tannins play a new role, altering the aquatic environment and the life therein.

Blackwater rivers have a very different chemistry than other water bodies. They are more acidic but lower in oxygen, nutrients, and the dissolved elements many animals need (Ribeiro and Darwich 1993). There are, therefore, fewer animals in blackwater than in clearwater or whitewater. Snails and some other invertebrates, for example, need calcium to build their shells, and these do not fare well in low-calcium blackwater rivers. With fewer invertebrates to eat, fish and other predators are relatively scarce. Yet there is life in blackwater, and although it is a bit harder to find, it is unique and, in its own way, amazing.

A bdelloid rotifer. Photo by Donald Hobern, licensed under CC BY 2.0.

A bdelloid rotifer, found in a wet clump of moss. Photo by Donald Hobern, licensed under CC BY 2.0.

The deformed-zucchini-shaped thing above is in fact an animal, smaller than a grain of sand, called a rotifer. Rotifers can be found almost anywhere with moisture, though you’d need a microscope to spot them. They feed on tiny particles of all kinds, from bits of detritus and algae to bacteria and other single-celled organisms. Despite being tiny, rotifers are relatively complex creatures with minute brains, feelers, and a large mouth surrounded by hair-like appendages called cilia. Some species even have simple eyes.

When a rotifer wishes to swim, it simply vibrates the cilia to pull its body forward. The cilia are also important in feeding — if the rotifer is anchored by its “tail” end, the vibrating cilia create a water current that draw particles towards the mouth. Rotifers eat pretty much the same way street-sweepers sweep. Below is a video of what this looks like:

[Video credit is to “NotFromUtrecht,” licensed under CC BY-SA 3.0.]

In the Amazon Basin, blackwater is dominated by rotifers which, unlike many planktonic invertebrates, do not need calcium or other dissolved minerals to construct cells. At the junction of the Rio Negro and the Amazon River, rotifer populations can be up to ten times higher in the blackwater than in whitewater (Ribeiro and Darwich 1993), even though the two extremes are separated by only a few feet of transition. The same pattern exists in Argentina, where a different “Rio Negro” (also blackwater) meets the whitewater Rio Salado (Frutas 1998).

As long as there are rotifers and other blackwater-tolerant plankton around, fish can also live in blackwater, but low nutrient and oxygen levels make it difficult for them to do so. Still, some very special fish have evolved to tolerate blackwater, and perhaps the most recognizable of these is the neon tetra, a fish made famous by its popularity in home aquariums.

The neon tetra (Paracheirodon innesi), a popular aquarium fish. Photo by Holger Krisp, licensed under CC BY 3.0.

The neon tetra (Paracheirodon innesi), a popular aquarium fish. Photo by Holger Krisp, licensed under CC BY 3.0.

In Rio Negro (Brazil, not Argentina), fish are not especially abundant, but many of the species that live there are endemic. Of the 700 or so fish known from the river, around 100 are found nowhere else on earth. Among these fish is the cardinal tetra, a close relative of the neon tetra with similarly vivid red and blue streaks. Another is the cururu, a freshwater stingray.

Freshwater stingrays are common in the Amazon Basin, where they are considered to be more dangerous even than piranhas. The greatest abundance and diversity of stingrays is found in the whitewater, but surveys have revealed there are several species that prefer blackwater, and at least two in the genus Pomatotrygon are found exclusively in the blackwater of the Rio Negro (Duncan and Fernandes 2010). One of these is the cururu ray, a unique species that has only been discovered in the last decade.

One of the cururu ray's closest relatives, the porcupine river stingray (Potamotrygon histrix). Photo by Jim Capaldi, licensed under CC BY 2.0.

One of the cururu ray’s closest relatives, the porcupine river stingray (Potamotrygon histrix). Photo by Jim Capaldi, licensed under CC BY 2.0.

Studying the cururu ray has helped us understand what is required for a fish to thrive in blackwater. First, the extremely low levels of sodium, chlorine, and other salts in blackwater presents a problem, since fish and all other animals require salts to keep their bodies running. The cururu, like many fish in Rio Negro, can survive with far less sodium and chlorine than most other fish, but it is also more efficient at extracting salts from the water, however scarce they may be (Wood et al. 2002).These rays also have gills with finger-like projections, adapted to be as efficient as possible in gathering both salts and oxygen from blackwater (Duncan et al. 2010).

Although scientists have known for some time that the cururu ray represents an undescribed species, it has yet to be given a Latin name. Many more new species may yet be discovered in the tannin-soaked waters of Rio Negro and other blackwater rivers. Unique places yield unique creatures, often with amazing stories.

Cited:

Duncan W.P. and M.N. Fernandes. 2010. Physicochemical characterization of the white, black, and clearwater rivers of the Amazon Basin and its implications on the distribution of freshwater stingrays (Chondrichthyes, Potamotrygonidae). Pan-American Journal of Aquatic Sciences 5(3): 454-464.

Duncan W. P., O.T.F. Costa, M.M. Sakuragui, and M.N. Fernandes. 2010. Functional morphology of the gill in Amazonian freshwater stingrays (Chondrichthyes: Potamotrygonidae): implications for adaptation to freshwater. Physiological and Biochemical Zoology 83: 19-32.

Frutos S.M. 1998. Densidad y diversidad del zooplancton en los Rios Salado y Negro — planicie del Rio Parana — Argentina. Revista Brasileira de Biologia 58(3): 431-444.

Janzen D.H. 1974. Tropical blackwater riversm animals, and mast fruiting by the Dipterocarpaceae. Biotropica 6(2): 69-103.

Ribeiro J.S.B. and A.J. Darwich. 1993. Phytoplanktonic primary productivity of a fluvial island lake in the Central Amazon (Lago do Rei, Ilha do Careiro). Amazoniana 12(3-4): 365-383.

Wallace A.R. 1853. Narrative of travels on the Amazon and Rio Negro. Reeve, London.

Wood C.M., A.Y.O. Matsuo, R.J. Gonzalez, R.W. Wilson, M.L. Patrick, and A.L. Val. 2002. Mechanisms of ion transport in Potamotrygon, a stenohaline freshwater elasmobranch native to the ion‐poor blackwater of the Rio Negro. Journal of Experimental Biology 205: 3039–3054.

The Wanderer

by Joseph DeSisto

Night, and the Sonoran Desert comes to life. Lizards and mice emerge from their hideaways to eat, fight, and mate, while scorpions and giant centipedes scuttle about, hoping to stumble upon a juicy insect meal. All the while, a female tarantula waits in her burrow.

A Texas blonde tarantula, perched eagerly at the edge of her burrow. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

A blonde tarantula from Arizona, eagerly perched at the entrance to her burrow. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

She has no need for sight or smell. She only has to feel — lines of silk trace the ground around her burrow, and she keeps her feet on these silk lines to feel every vibration.  A pair of lizards chase each other, dangerously close to the burrow, and the spider flinches in predatory excitement, but bides her time. A few seconds later, a june beetle, weary from a night of flying, lands by the entrance and takes a few ill-fated steps. Crunch!

A Texas blonde tarantula with june beetle prey. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

A blonde tarantula with june beetle prey. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

Tarantulas are found all over the tropics and subtropics, from rainforests to mountaintops to deserts. The blonde tarantulas of North America’s deserts, in the genus Aphonopelma, are some of the toughest and longest-lived arachnids on earth. Females reaching maturity after a decade, and can live another several years after that. The longest-lived specimen known to science survived for more than 17 years (Ibler et al. 2013).

The female blonde tarantula spends nearly her entire life underground, in a short vertical burrow. This burrow, and the patch of earth around it, is her entire world — for ten years or more she ambushes and feeds on beetles, scorpions, and other unlucky passers-by. As a result, females are seldom seen except by those curious enough to wander through the desert flipping large rock slabs and inspecting the bases of bushes.

A female blonde tarantula. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

A female blonde tarantula. Photo by Michael Wifall, licensed under CC BY-SA 2.0.

During my trip to Arizona this summer, I only found one. I provoked her with a blade of grass, to see if she would leave her burrow. Even though her home was all but destroyed by my rock- flipping, this spider adamantly refused to leave. She held her ground, furiously biting and lashing out with her front legs.

Male blonde tarantulas are much more easily seen, and during my trip to Arizona I found several crossing roads at dusk. For the first one, I stopped and left my car to get a closer look, eager to see what this amazing creature was all about.

A male Arizona blonde tarantula, likely Aphonopelma chalcodes. Photo by Joseph DeSisto.

A male Arizona blonde tarantula, likely Aphonopelma chalcodes. Photo by Joseph DeSisto.

Tarantulas are big — this one had a leg-span approaching five inches. It was easy to coax him into a jar, since without a burrow to defend, blonde tarantulas are quite docile animals. Had I been a little braver, I probably could have picked him up without being bitten. If I had failed, the bite would have been painful, but no more dangerous than a bee sting.

Compared to the female tarantula, the male is leaner, with a smaller body and longer, skinnier legs. The sexes are also different in another respect: experiments have shown that when at rest, male blonde tarantulas can get by on significantly less oxygen than their mates (Shillington 2005).

There’s a good reason for that. At around ten years of age, while females remain in their burrows, males reach sexual maturity and begin the “wandering phase” of their lives. When he is ready to mate, a male blonde tarantula emerges from his burrow and strides off into the desert in search of a female.

A wandering male blonde tarantula from Texas. Photo by Dallas Krentzel, licensed under CC BY 2.0.

A wandering male blonde tarantula from Texas. Photo by Dallas Krentzel, licensed under CC BY 2.0.

The desert is a big and lonely place, and female tarantulas may be few and far between. Here a male’s athletic prowess comes in handy: males that can walk the longest and fastest without tiring are the most likely to find a not-yet-mated female. This is important, since a female who has already mated might prefer to eat him rather than entertain a second suitor.

During his walk-about, a male blonde tarantula faces many hazards, from spider-eating birds and  wasps to the desiccating sun and wind. Nothing but death can dissuade a male from his journey. Texas tarantulas with radio transmitters have revealed that while some can get by traveling only a short distance, others may journey more than two miles over a period of several weeks (Stoltey and Shillington 2009).

A male tarantula from New Mexico. Photo by Robert Sivinski, licensed under CC BY-NC 3.0.

A male tarantula from New Mexico. Photo by Robert Sivinski, licensed under CC BY-NC 3.0.

My road-crossing specimen didn’t take to captivity very well. I provided him with plenty of room, soil and a place to hide, but all he could do was pace, back and forth across his cage. He did not eat or rest — he only walked. Finally I took pity and released him, and watched my eight-legged friend stumble back into the desert.

If a male blonde tarantula fails to find a mate, he will simply walk until he dies. If he does manage to reach a female’s lair, and he is lucky, she will mate with him. After, she might eat him, or she might not. It depends on how she’s feeling. The outcome hardly matters to the male. If she eats him, his body will be a final, nutritious gift to his offspring, yet to develop inside her. If she allows him to live, he will simply return to the surface, stretch his hairy legs, and keep walking.

Cited:

Ibler B., P. Michalik, and K. Fischer. 2013. Factors affecting lifespan in bird-eating spiders (Arachnida: Mygalomorphae, Theraphosidae) — a multi-species approach. Zoologischer Anzeiger – A Journal of Comparative Zoology 253(2): 126-136.

Shillington C. 2005. Inter-sexual differences in resting metabolic rates in the Texas tarantula, Aphonopelma anax. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 142(4): 439-445.

Stoltey T. and C. Shillington. Metabolic rates and movements of the male tarantula Aphonopelma anax during the mating season. Canadian Journal of Zoology 87: 1210-1220.

Silver and Green

by Joseph DeSisto

Sunlight in the western U.S. can be intense, and all the more so when it catches the shimmering green carapace of a jewel scarab:

A Beyer's jewel scarab from Arizona. Photo by Joseph DeSisto.

A Beyer’s jewel scarab from Arizona. Photo by Joseph DeSisto.

The regal purple legs of this beetle identify it as Beyer’s jewel scarab (Chrysina beyeri). Beyer’s jewel scarabs spend most of their lives as white grubs in rotting logs, where they slowly eat their way through the wood. When they finally emerge as adult beetles, they eat oak leaves.

Although nearly a hundred jewel scarab species are found in Mexico and Central America, only four are known from the U.S.A., all in the southeastern portion of the country. Probably the most visually stunning is the so-called glorious jewel scarab (Chrysina gloriosa), with a lime-green exoskeleton sporting thick stripes of metallic silver.

The glorious jewel scarab, also from Arizona. Photo by Joseph DeSisto.

The glorious jewel scarab, also from Arizona. Photo by Joseph DeSisto.

There is something truly awe-inspiring about a beetle in which you can see your own reflection. We know that, of course, the glorious jewel scarab is not beautiful for our own gratification, but what adaptive purpose could metallic stripes possibly fulfill?

There are likely two. First, the glorious jewel scarab feeds on the leaves of juniper trees, which are common in the beetle’s high elevation habitats in Arizona and Texas. Juniper trees have tiny leaves along narrow branches, and thin strips of sun can create a shimmering effect at the right time of day. The beetle’s shining armor may actually serve as camouflage, by mimicking the narrow rays of sunlight that flicker through the trees.

A glorious jewel scarab on its host, juniper. Photo by Robert Potts, licensed under CC BY-NC-SA 3.0.

A glorious jewel scarab on its host, juniper. Photo by Robert Potts, licensed under CC BY-NC-SA 3.0.

Another Arizona insect uses the same trick. The royal moth’s caterpillar (Sphingicampa) is large and green, with a red stripe on each side and metallic spines jutting out of its back. Yet on their host plants, these caterpillars are well camouflaged. How? Because the plants they live on (locust, acacia, and others) all have small leaves with tiny spaces between them. The spines on royal caterpillars mimic the spaces between the leaves, and the light that flows through them.

A Sphingicampa caterpillar, showing off its metallic spines. Photo by Joseph DeSisto.

A Sphingicampa caterpillar, showing off its metallic spines. Photo by Joseph DeSisto.

The other reason for metallic strips is less obvious. It turns out that jewel and a few other scarab beetles can be so shiny because their exoskeletons reflect a unique kind of light, called circularly polarized light. To understand that, we need to understand a bit of physics.

What we call light is actually the product of tiny packets of energy called photons, travelling through space at the speed of … light. Photons travel in waves, undulating up and down or side to side. Normally, each photon has a wave pointed in its own direction, but sometimes, all the waves are oriented the same way. In other words, all the waves are on the same plane:

When light is polarized, all photons have wavelengths with the same orientation. Figure in public domain.

When light is polarized, all photons have wavelengths with the same orientation. The red wave shows the path of photons in an example. Figure in public domain.

If all the waves are on the same plane, the light is said to be polarized. Polarized light is fairly common in nature — although humans cannot identify polarized light, many insects such as bees use it to orient themselves with respect to the sun. This allows them to navigate between flowers, and to and from their hives.

Circularly polarized light, on the other hand, is extremely rare. In this situation, waves are still on the same plane as each other, but the plane rotates. If you could see the photons as they traveled directly towards you, it would look like a single photon is moving in a spiral, but in fact many photons are moving together, each at slightly an angle to its neighbor:

In circularly polarized light, the plane on which the waves are travelling rotates. Figure in public domain.

In circularly polarized light, the plane on which the waves are travelling rotates. Figure in public domain.

I won’t belabor this — physics is not my strong suit and I would rather omit details than risk getting things wrong. The point is, it takes a very special and rare kind of surface to reflect light in this way — the surface of a jewel scarab.

That’s pretty cool by itself, but it also happens that the same beetles are one of the few animals that can see circularly polarized light. There are lenses that allow us to see the same light, and if we look at a glorious jewel scarab through one of those lenses, it will appear not green and silver, but black (Sharma et al. 2009).

This can help otherwise well-camouflaged jewel scarabs find mates. Experiments with glorious jewel scarabs have shown that they are attracted to and will fly towards circular polarized light (Brady and Cummings 2010). Closely related, but less flashy beetles show no such preference. So while a predator looks at a beetle-filled juniper tree and sees nothing but leaves and shimmering sunlight, beetles can easily spot each other as big, black, radiant spots in a green world.

The Beyer's jewel scarab. Photo by Robert Potts, licensed under CC BY-NC-SA 3.0.

The Beyer’s jewel scarab. Photo by Robert Potts, licensed under CC BY-NC-SA 3.0.

Cited:

Brady P. and M. Cummings. 2010. Differential response to circularly polarized light by the jewel scarab beetle Chrysina gloriosa. The American Naturalist 175(5): 614-620.

Vivek S., M. Crne, J.O. Park, and M. Srinivasarao. 2009. Structural origin of circularly polarized iridescence in jeweled beetles. Science 325: 449-451.

Living Illusions

by Joseph DeSisto

Good camouflage requires more than just color. Millions of years of natural selection have favored birds that can easily identify a brown moth on a brown background, but some species are a little more sophisticated. Lappet moths hide on tree bark – their odd shape, combined with mottled color, helps break up their outline, so visual predators such as birds have a hard time recognizing them as moths.

A lappet moth (Phyllodesma americana) from Arkansas. Photo by Marvin Smith, licensed under CC BY-ND-NC 1.0.

A lappet moth (Phyllodesma americana) from Arkansas. Photo by Marvin Smith, licensed under CC BY-ND-NC 1.0.

These moths lay their eggs on trees including birch, oak, poplar, willow, and many others. The caterpillars munch on leaves by night, hiding on twigs and bark by day. They are also well-hidden, but because they have to be able to live on a variety of different trees, each of which has a differently-colored bark, lappet caterpillars don’t have a color that matches a particular background. Instead they, like their parent moths, have bodies with distorted outlines, specifically a lateral fringe of long hairs.

On bark, this helps a caterpillar “merge” with the bark on which it rests. On a twig, maybe not so much:

A resting lappet caterpillar on one of its favorite hosts, scrub oak. Photo by Joseph DeSisto.

A resting lappet caterpillar on one of its favorite hosts, scrub oak. Photo by Joseph DeSisto.

Animals that depend on camouflage have to stay very still to avoid detection, but if they are spotted, staying still quickly becomes futile. Many animals use color to startle predators as a backup plan, the best-known example being the red-eyed tree frog. At rest, the frogs appear a solid leafy-green, but if disturbed, they quickly open their eyes. The sudden appearance of two giant, bright red eyes can be enough to startle a predator, which might give the frog time enough to make a hasty escape.

The iconic red-eyed tree frog (Agalychnis callidryas). Photo by Carey James Balboa, in public domain.

The iconic red-eyed tree frog (Agalychnis callidryas). Photo by Carey James Balboa, in public domain.

Lappet caterpillars have a similar but more elaborate trick. If a potential predator (or human finger) brushes against a caterpillar, it first flexes its body so the hairs on its back part. This reveals two striking, blood-red bands, a warning this caterpillar might be toxic.

Photo by Joseph DeSisto.

The lappet caterpillar has only to flex its body to reveal these striking bands. Photo by Joseph DeSisto.

Let’s say this doesn’t work, and the bird isn’t intimidated. If a bird’s beak (or my tweezers) pinches the caterpillar, it bends its head back over its body, revealing legs surrounded by pitch-black spots:

Photo by Joseph DeSisto.

This caterpillar doesn’t like me very much. Photo by Joseph DeSisto.

Still not startled? The lappet caterpillar has one last show. In desperation, it falls from its perch in the trees and, on hitting the ground, flops upside-down, revealing a bright yellow-and-black belly:

Photo by Joseph DeSisto.

Yellow and black are universal warning signs — many toxic animals share these colors. Photo by Joseph DeSisto.

If this doesn’t work, the caterpillar is pretty much toast. For all its show, the lappet caterpillar isn’t poisonous – at worst, some of its hairs are mildly irritating to the skin. Like the red-eyed tree frog, it relies entirely on visual illusions to ward off predators. It sounds risky, but it’s worked at least some of the time for millions of years.