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Etruscan Shrew (Suncus etruscus)

Etruscan Shrew (Suncus etruscus)

Alright, this is a little bit of a stretch for Etruscan week, but the Etruscan shrew (Suncus etruscus) is fascinating! It is the smallest mammal by mass weighing an average of only 1.8 grams (0.063 oz) (although there are certain bats with smaller skulls). The tiny creature does indeed live in what was once Etruria…although it admittedly also lives around the Mediterranean, throughout the Middle East, North Africa, Asia Minor, across Southeast Asia, and down into Malaysia.  There are also invasive colonies in Nigeria (though goodness knows how they got there).

Etruscan Shrew Range

Etruscan Shrew Range

The shrew has a fierce metabolism: its little heart beats 1511 times per minute (25 beats a second). It must eat up to twice its own body weight every day to stoke its internal fires. I like food–but I would wear down fast eating a thousand hamburgers a day. Once I watched a documentary about the top ten super predators—and shrews weighed in at number one. They only eat live food which they catch—and they catch between 20 and 30 prey animals a day. This becomes all the more impressive when one considers that they eat insects (which have wings and are sometimes bigger than the shrew) as well as spiders and myriapods which are armed with terrible stings and venoms. Additionally the shrew dines on immature amphibians, baby rodents, worms, and larvae.

Etruscan Shrew with Snail

Etruscan Shrew with Snail

Etruscan shrews are largely nocturnal and crepuscular. Because of their poor eyesight, they have acute hearing, highly sensitive whiskers, and an amazing sense of smell: indeed, their long tin noses are mobile and can move about quite sinuously. In winter their fur grows long and they sometimes undergo periods of temporary hibernation when their body temperature drops down to 12 °C (54 °F). They are only social during mating season when a pair will live together through the 27-28 day gestation and until the cubs are independent (which is when they are three to four weeks of age). Litters range from two to six cubs. Because they are so small (and so widespread), Etruscan shrews are preyed on by all manner of snakes, cats, lizards, birds, and other predators. Their particular bane seems to be owls. Naturally, none of these predators are as dangerous to the overall species as humankind is. Etruscan shrews now have a non-contiguous range because of agriculture and habitat loss (although they seem to enjoy human ruins). They live to two years of age in captivity—although owls usually prevent death from old age in the wild.

The Etruscan Shrew is cute in its own way...

The Etruscan Shrew is cute in its own way…

If we were not so jaded, we would recognize how remarkable and intense the Etruscan shrew is. Just writing about it, I feel like I have been describing an alien lifeform—a clever cunning creature which fits in a teaspoon. Except when it hibernates, it must endlessly devour. We will return to the art and society of ancient Etruria tomorrow, but right now spare a moment to reflect on the extraordinary nature of our strange mammal kin!

schmidt

Justin Orvel Schmidt (pictured above) is an entomologist who specializes in insect defenses.  His greatest expertise is in the stings of hymenopterans—the bees, wasps, sawflies, hornets, and ants (although he also researches the toxic/chemical defences of other arthropods).   In the early 1980’s Schmidt attempted to systematize the different medical and physiological effects of insect stings.  This work led him to coauthor one of the comprehensive tomes on the subject of insect venom Insect Defenses: Adaptive Mechanisms and Strategies of Prey and Predators.  Unfortunately for Schmidt, in the course of his researches, he has been stung/bitten innumerable times by various aggressive and toxic insects (and other creepy crawlies) from around the world.

Did you know that bullet ants look just like ants.  In a moment that fact will horrify you. ( Photo: Getty Images/Peter Arnold)

Did you know that bullet ants look just like ants? In a moment that fact will horrify you. ( Photo: Getty Images/Peter Arnold)

Based on these experiences, Schmidt attempted to categorize the algogenic (i.e. pain-inducing) effects of hymenopteran stings in the now world-famous Schmidt sting pain index.  This index is a captivating blend of subjective pain analysis, horrifying real world experience, and inventive poetry.   The lowest sting on the Schmidt index is a 0—betokening a sting which has no effect on humans. The highest rating is a 4 which describes an experience of maddening absolute agony.  The index became famous because of an interview with Outdoor magazine.  Schmidt has since conceded that his descriptive efforts lack an empirical basis and that stings vary depending on body location and the amount of venom injected.  Because of such admissions, Wikipedia took down its remarkable table of stings–which is a shame because the subjective descriptions gave the index its visceral power.  Here is a sampling copied verbatim from “Retrospectacle: A Neuroscience Blog”:

1.0 Sweat bee: Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm.

1.2 Fire ant: Sharp, sudden, mildly alarming. Like walking across a shag carpet & reaching for the light switch.

1.8 Bullhorn acacia ant: A rare, piercing, elevated sort of pain. Someone has fired a staple into your cheek.

2.0 Bald-faced hornet: Rich, hearty, slightly crunchy. Similar to getting your hand mashed in a revolving door.

2.0 Yellowjacket: Hot and smoky, almost irreverent. Imagine W. C. Fields extinguishing a cigar on your tongue.

2.x Honey bee and European hornet: Like a matchhead that flips off and burns on your skin.

3.0 Red harvester ant: Bold and unrelenting. Somebody is using a drill to excavate your ingrown toenail.

3.0 Paper wasp: Caustic & burning. Distinctly bitter aftertaste. Like spilling a beaker of hydrochloric acid on a paper cut.

4.0 Pepsis wasp: Blinding, fierce, shockingly electric. A running hair drier has been dropped into your bubble bath.

4.0+ Bullet ant: Pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel.

While the work lacks rigorous empirical criteria, even the most relentlessly analytical critics seem to aver that being stung by over 150 different species of arthtopods gives Schmidt a certain robust validity.  The literary merit of the metaphors is certainly genuine (although one hopes that the good Doctor Schmidt never actually dropped a hair dryer into his bubble bath or let misanthropic vaudevillians torture him with fire).   Personally I have only been stung by sweat bees, honey bees, and yellow jackets, so I cannot testify to the more esoteric sting ratings (thankfully–since yellowjacket stings nearly did me in), however something sounds completely right about the yellowjacket sting description.  I recall a moment of warmth which metastasized almost immediately into a sour panic-inducing pain which spread through my arm and then my body.

A Yellow Jacket Sting (photo credit: Richard Martyniak)

A Yellow Jacket Sting (photo credit: Richard Martyniak)

In conclusion, I salute Justin Orvel Schmidt as a man of science and a masochistic poet/performance artist.  If he claims that a bullet ant sting is the worst hymenopteran sting, I see no cause to contradict him and I never want to think about it again.

Have you ever watched a tiny red ant scurrying through the backyard only to be astounded that the ant seems like a giant when it walks by some much smaller black ants?  Such observations have always caused me to wonder how small insects could become.  What are the smallest insects out there and just how tiny are they?   The answer is actually astonishing, and, like most good answers it just brings up more questions.  Most entomologists believe the tiniest living insects are the fairyflies, infinitesimally minute parasitoid wasps which live on or inside the tiny eggs of thrips(well, some fairflies also live inside the brains of other insects, but let’s not think about that right now).  Fairyflies are smaller than many single cell organisms like paramecia, amoebas, and euglenas.    Dicopomorpha echmepterygis,  a wasp from Costa Rica, is an astonishing  .13 millimeters in length.   Although many of these wasps fly, they are so tiny that they don’t have conventional wings:  some of the smaller specimens have long cilia-like hairs which they use to row through the air (the fluid dynamics of which are considerably different for creatures so small).

Fairy wasp with single celled organisms under electron microscope

In fact the wasps are so tiny that the millions of individual cells which make up their tissues and organs have to be very miniscule indeed.  In fact, according to physics, the brains of fairyflies should not work.  Many of the neural axons are smaller than 0.1 micrometre in diameter (and the smallest axons were a mere 0.045 μm).  At such sizes, the electrical action of axons should not work properly.   An article on Newscientist describes the basic problem:

 …according to calculations by Simon Laughlin of the University of Cambridge and colleagues, axons thinner than 0.1 μm simply shouldn’t work. Axons carry messages in waves of electrical activity called action potentials, which are generated when a chemical signal causes a large number of channels in a cell’s outer membrane to open and allow positively charged ions into the axon. At any given moment some of those channels may open spontaneously, but the number involved isn’t enough to accidentally trigger an action potential, says Laughlin – unless the axon is very thin.

So how do the wasps continue to fly around and parasitize the eggs of other creatures if the electrical impulses of their brains do not work?  German researchers speculate that the axons of wasp brains work mechanically rather than electrically.  The tiny axons touch each other physically instead of by means of electrical action.  If this is correct it means the wasps are analogue creatures with little clockwork minds!  If they were any larger or more complex, this would not work, but because of their small size and simple drives, they can manage to operate with slow-moving machine-like brains.

Micrograph of a fairyfly (fairy wasp)

Agriculture is almost unknown in the natural world. Human beings are the only vertebrates known to grow crops or keep livestock (with the possible exception of damselfish which carefully tend little algae gardens).  And yet we were not the first animals to invent the concept.  Ants have farmed fungi within their tunnels for tens of millions of years.  Ants also keep aphids in captivity in order to “milk” them of sugary secretions–or to eat them outright.  It is possible that beetles, termite, or snails came up with the concept first, but most evidence points to ants as the first farmers.

An Ant Milking Aphids

Ants do not have a shabby operation either. Leaf cutter ants form the largest and most complicated animal societies known on Earth (other than our own) and a single colony can have over 8 million individuals.  Leaf cutters are an ideal example of how adept ants are at farming fungi.  Four different castes of worker ants work together to bring back leaf fragments and integrate them into huge fungal gardens. Different species of leafcutters cultivate different fungi from the Lepiotaceae family.  Certain bacteria with antifungicidal and antibacterial properties grow within the metapleural glands of the ants.  The worker ants use these bacteria to “prune and weed” dangerous or unproductive organisms out of their gardens.  Older (more expendable) worker ants carry waste products from the hive to a waste pile where they stir the hive wastes together to aid in decomposition.  The waste-management job brings the danger of fungal or bacterial contamination and contaminated ants are exiled to certain death in order to keep the gardens safe.  Additionally dead ants from within the hive are carefully placed around the waste pile so as to protect the hive from their decomposition.

Leaf Cutter Ants at the Cameron Currie Lab arrange cut-up leaves into their fungal garden.

According to geneticists who study the rates of mutation within the various fungal cultivars, ants began their farm relationship with fungi around 50 million years ago in the warm Eocene epoch (an era which saw many of the critical relationships in modern ecosystems begin).

 

Digital Cut-away of an underground leaf-cutter nest

Scientists are also beginning to understand the means by which ants herd their little flocks of aphids.  The aphids are smaller insects which feed on the saps and juices of plants (which they suck out by means of specialized mouthparts called stylets).  The ants prevent the aphids by flying away by tearing off their wings.  The feet of the ants produce chemicals which tranquilize and subdue the aphids and keep them from escaping the “pastures” near the ant colonies.  It is believed that aphids also derive certain benefits from this arrangement since the aggressive ants protect them from many of their natural predators.

An Ant with a “herd” of Aphids

For years naysayers belittled the farming achievements of ants suggesting they were little more than symbiotic arrangements.  However as entomologists study the ants more carefully they increasingly discover just how complicated and sophisticated those relationships are (involving as they do numerous symbiotic relationships with bacteria in order to produce the chemicals necessary for agricultural control).  Additionally, what are humankind’s relationships with our crops and animals if not huge harrowing examples of symbiosis?

An Iridescent Wasp on a Linen Tablecloth

Today I would like to start a brand new animal category concerning the most gifted of the social insects, the superorder Hymenoptera, which consists of wasps, bees, ants and sawflies (along with some other oddballs which are less frequently mentioned).  Hymenoptera are arguably among the most successful creatures on the planet.  Their behavior can be almost embarrassingly humanlike and they are famous for building elaborate constructions, going to war, taking slaves, farming fungi, and crafting rigid city-like social hierarchies. However, of all life forms on earth, the hymenoptera are some of the most vividly alien: cuttlefish do seem downright cuddly when compared to the horrifying digger wasps.   A sociologist could happily draw parallels between a bee hive and a city until he looked at the details of bee reproduction, at which point he would probably break down and weep.

The Hymenoptera are not as ancient as either the mollusks or the mammals (if it is fair to compare an order with a phylum or a class).  They originated in the Triassic and did not develop the successful social organization which is now such a defining feature until the late Cretaceous.   The first hymenopterans were the xylidae, a family of sawflies with a minimal presence on earth today but with a long pedigree. These first sawflies fed on the pollen and buds of the conifer stands beneath which the first dinosaurs developed (and under the roots of which the first mammals cowered).  The rise of the flowering plants in the Cretaceous led to a leap-forward for these pollen-eaters: complex flowers then evolved in tandem with the hymenopterans. It was also during the Cretaceous that the ants and termites split from the vespoid wasps.  The earliest honey bees of the familiar genus Apis evolved at the end of the Eocene bt they were preceded by all sorts of hymenopteran pollinators.

A Sawfly Fossil (Hymenoptera: Symphyta)

I mentioned above that, for all of their familiarity to us, the Hymenoptera are disturbingly alien.  In fact as I have been writing this comparatively tame post, a dreadful sense of formication has stolen over me and I find myself brushing phantom ants from my limbs and feeling the terrible pang of yellowjacket stings from childhood.  The hymenoptera are frequently the basis of the extraterrestrial enemies in science fiction.  Although people are occasionally stung to death by wasps or ripped apart from within by driver ants, it is something larger and less tangible which makes the hymenoptera such reliable villains. I have watched the soldier bees snip the wings off of wasps trying to invade my grandfather’s bee hive and then toss the invaders’ writhing bodies from the painted ledge—all while a river of worker bees went out and came back laden with pollen.  There is an alarming touch of civilization to these social insects: a hint that they are utilizing the same kinds of organization and communication which have made humans such a success.  And, in fact, the social insects are a huge success—ants alone are estimated to constitute a substantial portion of the animal biomass of earth (to say nothing of termites, bees, wasps and the rest).

Yellow Jackets on a Coke Can (photo by the fearless Alan Cressler)

Of course this success has broad ramifications. The hymenoptera are everywhere in nature and they also play a huge part of human culture. Indeed the very name of this blog is a play on words between my surname and the noble art of aviculture.  Without the bees, we would not have much in the way of fruit or vegetables.  Not only would this be a disaster for human farming—just contemplate how many other creatures rely on those fruit!  Similarly the ants bulwark an entire portion of the ecosystem by scavenging the tidbits out of fields and forests.  Writing about the hymenoptera may be an itchy, antsy business but it is a well-merited study.  This group of insects is pivotal to life on dry-land as we know it.  The biblical promised land was one of milk and honey.  There would be no milk without mammals, but there would be no honey (and precious few mammals) without the hymenoptera.

A beekeeper completely covered with swarming honey bees in a “bee man” cantest in China

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