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red-eyed-wasp.jpg
Researchers have used gene manipulation to create an amazing new mutant wasp with horrifying blood red eyes! A team of scientists at University of California Riverside used CRISPR gene-slicing technology (which sounds more like a salad technology than something used for wasps) in order to permanently alter the eyes of the tiny parasitic jewel wasps (Nasonia vitripennis). Researchers injected DNA and RNA into the nearly microscopic wasp eggs with infinitesimal needles. The resulting red eyes are hereditary and can be passed through successive generations.

The scientists hope to understand how male jewel wasps can somehow ensure that all of their offspring are male—a very unusual ability which geneticists and entomologists would like to understand. However, beyond novelty eye color and sex selection in tiny obscure parasitoid wasps, the researchers are also after bigger game—understanding how to manipulate the genes of all sorts of insects including agricultural pests and dangerous disease-carrying bugs like mosquitos and tsetse flies.

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)

A “Zombee” tattoo (by Josh Herrera of Skin Factory in Las Vegas)

More bad news for honeybees: not only do our hard-working black-and-yellow friends have to contend with blood sucking varroa mites, neonicotinoid insecticides, and giant hungry bears, but a new plague has been spreading from the west coast, claiming the life of domestic honey bees.  The Zombie fly (Apocephalus borealis) is a disgusting little hunchbacked phorid fly which has traditionally preyed on native wasps and bumblebees.  Phorid flies, coincidentally, are a successful family of over 400 species of tiny flies which tend to run very rapidly (although they are capable of flight).  The most famous phorid fly (insomuch as that’s a thing) is probably the coffin fly—although the zombie fly is working its way into the limelight too.  Charming!

The parasitic fly Apocephalus borealis on the back of a bumble bee (photo by Kimberly G. O’Harrow)

Like the horrifying parasitoid wasps, the zombie fly uses its syringe-like ovipositor to inject its eggs inside of its victims.  As the larvae hatch they attack the bee’s brain and cause it to behave in bizarre manners—such as lurching around in a random fashion or flying at night (which gets the bee away from the hive and ensures that the fly lavae are not destroyed by the bee’s concerned colleagues).  Bees so affected are mordantly known as “zombees” for obvious reasons.  Eventually the zombie fly larvae pupate into hard little cocoons which resemble grains of rice.  When they hatch they rip through the bee’s body at the juncture of the head and thorax, frequently decapitating the bee.  Sometimes it is difficult to enjoy the beauty of nature.

Adult female Apocephalus borealis fly (image from Core A, Runckel C, Ivers J, Quock C, Siapno T, et al. (2012). “A new threat to honey bees, the parasitic phorid fly Apocephalus borealis”. PLoS ONE 7 (1))

It is unclear to what extent zombie flies are contributing to the decline of honeybees at large–since the flies have not traditionally attacked domestic bees.  Perhaps the death and decline of other native bees has pushed the zombie flies into this new behavior (or maybe they were getting around to it anyway—they sound like thoroughly repulsive customers).  At any rate, beekeepers have a new problem to worry about, and are tracking confirmed instances of “zombees” online at www.zombeewatch.org.

A female velvet ant (mutillidae wasp)

Velvet ants (Mutillidae) are not actually ants at all—the insects are classified as wasps even though female velvet ants do not have wings and appear to be tiny furry colorful ants. The Mutillidae family of wasps—which is made up of more than 3000 species– illustrates how closely wasps, bees, and ants are actually related.   Male velvet ants look nothing like the females but are much larger winged creatures resembling other wasps.  So great is the sexual dimorphism between the genders that it took entomologists a tremendously long time to pair the females with the males, and in many species the connection has still not been made by science.  The genders do however both share a ridged structure called a stridulitrum, which can be rubbed or struck to produce chirps and squeaks for communication.

Male velvet ant (mutillidae wasp)

Female velvet ants are notable not just for their colorful fur but for their tremendously powerful sting which is so painful that they are nicknamed “cow killers.”  Male velvet ants look like wasps but do not sting.  The exoskeletons of velvet ants are tremendously hard to such an extent that some entomologists have reportedly found it difficult to drive pins through specimens.  The dense hard coating helps the females invade the underground burrows of larger bees and wasps which the velvet ants sting and lay eggs on.  When the velvet ant larvae hatch they feed on the paralyzed victims before metamorphosing into adult form and venturing into the world.

Blue velvet ant (female)

Velvet ants are found in warmer parts of the world particularly deserts.  The majority of species are red and black but a variety of other colors are known including blue, gold, orange, and white.  Unlike the social ants and termites, velvet ants are generally solitary, coming together only to reproduce with their strangely alien mates.

Copidomopsis floridanum injecting its eggs into a caterpillar.

Sometimes horror is a matter of perspective.  For example, parasitoid wasps–some of the most horrifying hymenoptera–are also some of the most beneficial to humankind. The parasitoid wasps are a hugely diverse superfamily among the hymenoptera consisting of more than 6000 different species.  These insects are ancient, successful, and profoundly useful for controlling invasive species or pests (particularly various arthropods), however as soon as one knows what “parasitoid” means it becomes difficult to regard these wasps without revulsion and distaste. A parasitoid is a creature which lives inside another creature (the host) and ultimately kills/destroys that host by consuming it or by bursting out of it.  The detailed dynamics of this relationship are often grisly in the extreme, but they highlight the bizarre (not to say disturbing) mutualism which is such a feature of the natural world.

The emerald cockroach wasp or jewel wasp (Ampulex compressa)

Parasitoid wasps are especially alarming because of the extent to which they can manipulate the behavior of their host.  For example the emerald cockroach wasp (Ampulex compressa) is a solitary hunting wasp which finds a single cockroach and delivers a mildly paralytic sting to the roach’s thorax.  This first sting temporarily incapacitates the roach and allows the wasp to carefully make a second more meaningful sting to a precise spot in the roach’s brain which control’s the roach’s escape response. Not only does the wasp know where to sting, she utilizes a toxin which specifically blocks receptors for the neurotransmitter octopamine. The wasp then chews off a portion of the roach’s antennae and returns to her layer leading the captive roach by holding its damaged antenna like a leash. Inside the wasp’s burrow she plants a single egg on the roach’s belly and then seals the zombified insect inside the chamber with sand and pebbles.  After three days the wasp’s egg hatches and the new larva feeds for 4–5 days on the external portions of the roach.  It then burrow inside the still living roach and devours the creature’s organs in a progression which leaves the roach alive for a maximum length of time.  When the roach is near death the wasp larva builds a cocoon inside it, metamorphoses into an adult, and then bursts out of the roach carcass and flies off.

Aaaagh!

Across the many different parasitoid wasps there are many variations of this behavior involving different arthropod hosts–and specifically targeting the host’s eggs, lava, or adult form.  Additionally there are sundry vectors by which the parasitoid wasps control their hosts.  Not all wasps utilize targeted neuropoisons like the emerald cockroach wasp.  Wikipedia elaborates on how close the biochemical relationship between the parasitoid wasps and their hosts can become:

Endoparasitoid species often display elaborate physiological adaptations to enhance larval survival within the host, such as the co-option of endosymbiotic viruses for compromising host immune defenses. These polydnaviruses are often used by the wasps instead of a venom cocktail. The DNA of the wasp actually contains portions that are the templates for the components of the viral particles and they are assembled in an organ in the female’s abdomen known as the calyx.

In other words some wasps utilize ancient hunks of rogue DNA to directly or indirectly control (and then destroy) their host organisms.

Braconid wasp lavae (Cotesia congregatus) destroying a tomato hornworm

The biochemical sophistication of the parasitoid wasps does not end there.  Certain wasps seem to have a symbiotic relationship with plants.  When these plants are gnawed by harmful insects (especially beetles or caterpillars) the plants release specific chemicals which summon the parasitoid wasps, which, in turn, destroy the insects. An example of this can be found in that most ubiquitous of American staple crops, corn.  When beet armyworm caterpillars  (Spodoptera exigua) start eating a live corn plant, it releases a chemical which attracts  parasitiod wasps of the species Cotesia marginiventris (the larvae of which utilize beet armyworm caterpillars as hosts). If however the corn is invaded by corn earworns (Helicoverpa zea) it will release a different chemical which attracts a different   wasp Microplitis croceipes.  As scientists look further into such relationships, they are discovering that most plants have a vast range of chemical tags which are appealing to specialized parasitoid wasps (and to sawflies).  Perhaps one of the reasons that various blights have been able to make such deep incursions in new ecosystems is the absence of plants’ terrifying little friends.

Cotesia marginiventris on a corn leaf

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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