The world of tiny animals is a fascinating one.
Here you can find a diversity that simply wouldnt be possible on any higher level.
A seemingly endless supply of resources - a multitude of all kinds of micro ecosystems
and the amplified randomness of mother nature allow for life to develop in ways one can
hardly imagine.
The incredible diversity in flora and fauna caused countless animals to develop sophisticated
strategies for surival and reproduction that you can only find here.
A particularly gruesome reproductive strategy is employed by flies of the genus Pseudacteon.
Without a closer look, these flies don't seem to be very special or interesting.
Only between 1-2mm big - between 1/10th and 1/20th of an inch - about as big as a fruit
fly - with comparably large eyes and a prominent humped back (that gave the family of theses
flies the common name "humpback flies") most people probably wouldn't even take note of
them.
Only during egg deposition do they reveal their dark secret.
these flies inject their eggs into living hosts, more specifically into ants.
Each species of these flies is almost always restricted to a single ant genus - most of
the time even to a single ant species.
To insert their roughly 100-300 eggs female flies look for potential victims at disturbed
mounds or foraging trails.
After identifying a target the female goes into position, hovering a few millimeters
above the ant.
She is only as big as as the ants head but as swift as an arrow.
In less than a second she strikes the ant with her ovipositor - the elaborately shaped
stinger - inserting a single egg into the workers thorax.
Then she flies off looking for her next target.
After a few days the egg hatches and the the larva migrates to the ant's head where it
first feeds on the big muscles the ants use to open and close their powerful pincers and
then proceeds to devour the rest of the heads contents including the tiny brain causing
the ant to wander aimlessly for one or two weeks till it eventually dies of thirst.
At this point the larva - now filling up almost the entire head cavity - is ready to pupate.
Next it releases a chemical that degrades the membranes that hold the ant’s exoskeleton
together and causes the head to fall off.
This fact earned these flies the common name - ant-decaptiating-flies.
the next stage - the pupal devolpment - takes an additional 2-3 weeks.
During this time the pupa remains protected in the head capsule, completing its metamorphisis
into a fly.
At last the adult stage is reached and fly emerges from the oral cavity and flies into
the world.
Intersting also: The sex of the fly isnt determined by chromosomes but the size of the ants head.
larva that develop inside bigger heads devolp into females while larvae inside the heads
of smaller workers develop into males.
The total development time is 4-12 weeks depending on the temperature.
the adults, however, only live for around 3-5 days before they once again lay eggs and
die.
As horrifying as this way of reproduction might seems, it might actually be usefull
to us.
Amoung the numerous species of ants these flies parasitize are also several species
of fire ants, including the invasive red and black imported fire ants in the United States
which were both accidentally introduced from South America in the early 20th century and
are now major pests in the US, espeically in the southern states.
Because they have no real natural enemies in north america they were able to spread
and multiply rapidly to the point that there are now more introduced fire ants in north
america than they are fire ants in south america, where they originally came from.
In Texas alone they are causing $1 billion in damanges every year.
In an atempted to control their spread researchers began introducing ant-decaptiating-flies from
South America in Texas While the parasitism rates have been documented
to be very low - below 3% - the presence of these flies has been shown to serverely interrupt
fire ant foraging - leading to dramatic short-term decreases in resource retrieval.
Just one or two flies are enough to trigger an immediate defensive and evasive behavior
of a whole colony.
Six different species of these flies, each to combat one specific ant species, have been
released at numerous sites across the southern US since 1999.
And despite the intial concerend that introducing another non native animal is like fighting
fire with fire it didnt yet have unindended consequences.
The fact that these flies are highly host specific, only attacking ants from a single
species or a group of closely related species ensures that the indroced flies only attack
the intended fire ant species and dont negativly impact native ants or other animals.
Because these flies are parasitoids that rely on the ants for reproduction they will of
course never completely wipe them out but they could at least be an effective way to
control their population by creating an equilibrium between host and parasite.
Determining whether this actually works in practise will, however, take more time - perhaps
as much as a decade.