(Source: The Disney Store)
International team discovers bizarre and bewildering secrets of insect reproduction

For humans, sex is often counted in minutes not hours.  But if you're a Neotrogla aurora, sex is counted not in hours, but days.
I. Meet the Barkflies
It's well known that insects (and arthropods in general) have some bizarre mating and copulation behaviors.  Water striders lure predatory fish towards their potential mate, in an attempt to pressure her into having sex.  Female praying mantis' chomp off their much smaller male mate's head, which biologist believe helps the still barely-alive but brainless male to thrust more vigorously for the next several hours.
Male honeybees have barbed penises and mate in midair, only to have their male member dislodged at the end of the encounter, killing them in the process.  And male bedbugs inseminate females by stabbing them violently with a spear-like penis -- but often kill fellow males on accident due to their difficulty in telling their genders apart.

mating barkflies
Neotrogla aurora in the midst of a 70-hour lovemaking session. [Image Source: Current Biology]

But the recently discovered species of cave dwelling insect in Brazil offers at least an unusual mating habit, and in many ways is far more bizarre.  The critter in question is a winged member of the order Psocoptera -- an order of insects, known commonly as booklice, barklice or barkflies -- and the sex is even more extreme.  And this tiny creature's sex life packs one whopper of a bizarre twist.
An international team, led by senior author Charles Lienhard, a senior biologist at the Natural History Museum of the City of Geneva, and first author Professor Kazunori Yoshizawa -- a researcher who spends most of his time as an Earth Science professor at the Hokkaido University in Japan -- have watched and examined the sexual habits of the cave barkflies, publishing their results in a new study in the journal Current Biology.
The researchers reveal that the tiny insects provide a window into a world turned upside down, but on at least one level they do share one common thread with human reproduction.  In order to mate, one of the barkflies presents their potential mate with luxurious gifts, offerings that may improve their life and survival aspects.  And of course it is the male who provides these offerings to his female mate.
II. Dude Looks Like a Lady
But that's about where the commonality between mankind and these bizarre barkflies ends.  In a barkfly the male doesn't compete for ability to breed, it is the female who competes for both the gifts and right to copulate with her male mate.  And the "gifts" aren't a house, a car, or tuition for the kids -- they're a nutritious ejaculate that offers critical sustenance in the at-times barren and difficult cave environment.
And here comes the twist -- the males have the sexual cavity (a "vagina" of sorts) while the females have the extruded fleshy phallus ("penises" to us humans), which are used to pin the mate and engage in vigorous procreation.

Barkfly penis
The female cave barkfly has a phallus (penis) which she uses to penetrate her male mate.
[Image Source: Current Biology]

The male deposits his sperm in the form of a spermatophore (sperm sac).  This alone isn't unusual; male crickets and butterflies, as well as most arachnids, produce them.  But typically the male has the phallus that he uses to pin and inject the female.
Mating barkflies
The female's phallus inflates upon entering the male's fleshy pouch.
[Image Source: Current Biology]

The cave barkflies are in the extreme minority -- or perhaps unique -- in that the female has the phallus and pins the male during reproduction.  As is typical in these kinds of insects the female receives an ejaculate that she uses to fill the spermaphores.

Barkfly sacs
The male fills the female's sacs with sperm, which dangle in pairs near her phallus.
[Image Source: Current Biology]

Mating lasts a long time -- typically 70 hours, or roughly three days.  During this time the female can receive more than one spermaphore.  Typically she fills two spermaphores at once, which gives the startling mental visual of a female insect with a phallus and two sperm filled sacs.
Who says nature isn't full of surprises?
III. Spiny Penises Prevent Male From Escaping
A final interesting note on the cave barkflies: during copulation the female clutches the male with her parapods (belly protrusions). However, the primary form of anchoring are spines in the phallus which impale the male from the inside during mating, pinning him.  These spines attach as the phallus inflates via blood flow at the start of mating.  
The grip is intense. The researchers describe:

Furthermore, pulling apart coupled specimens (N. curvata: n = 1) led to separation of the male abdomen from the thorax without breaking the genital coupling, showing that the female can hold the male tightly using the gynosome and paraprocts.

In other words, attempting to remove the female from the male during mating may prove deadly to the male.  Ouch!
The good news for the male is that despite being penetrated and stabbed by his lover's barbs, he at least typically survives the ordeal, a far better fate than he would face were he a mantis.  

Barkfly mating
During the mating process, the female uses her spines to barb the male, pinning him in place while she has her way with him. [Image Source: Current Biology]

The males, as you might guess, are on the bottom.  But this is actually typically the case, even in the case of the rest of the insect world where the male posseses the phallus.  Writes the researchers:

As in most related taxa, including those having well-developed male genitalia ( Figure 1C) [ 8], the male is positioned under the female during copulation ( Figure 1A).

Most primates have similar structures (but in the male phallus), which serve to not only hold the female firmly, but also to penetrate through other males' hardened ejaculates.  Humans somehow lost our spiny penises during the evolutionary process.
The cave barkfly only known species in which the male possesses a true mating pouch (male seahorses have an incubation pouch, but mating occurs via the traditional means) and the female possesses a phallus.

Bugs Life
We're guessing the cave barkfly won't be included in the next Disney movie, but you never know.
[Image Source: Disney Store]

Why is this so uncommon? Biologists believe that in most cases eggs take much more energy to produce than sperm.  But in the extreme environment of the cave, where food is scarce, that difference may not matter as much as picking the fittest mate.  So the researchers believe that natural selection favored the male -- a more aggressive food gatherer -- forcing the females to court it and only picking the fittest members to receive the rewards of its labors.
That in turn suggests that if sexual reproduction is one day observed on alien worlds that harbor life, it might be the males that have the vaginas, and the ladies that have the penises.
That kind of gives a whole new frightening meaning to Nobel Prize-winning physicist Stephen Hawking's suggestion that aliens will likely "conquer" mankind, doesn't it??
(The other authors on the study were Professor Rodrigo L. Ferreira of the Federal University of Lavras, Brazil and biology Professor Yoshitaka Kamimura of Keio University in Yokohama, Japan.)

Source: Current Biology

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