Male secrets: coremata, penis, phalloblaster and... alcohol

Community and Forum → Blog → Male secrets: coremata, penis, phalloblaster and... alcohol

Lev Bely, 10.01.2014 16:21

This pic caused a great interest: excuse me, what is this? This terrific infernal thing outthrusting of a poor moth? Not the first come to mind. This is called coremata (Greek) which is originally means “feather duster”, an eversible scent gland of some male moths. Many of Arctiidae moths are proud owners of such gland.

Coremata of Chionarctia nivea male moth:

As leps don't live in a commune-style, side by side, it can be quite a task for them to find a proper mate of the same species. So they start “signal fires” launching pheromones into the air which are produced by that very magic gland. To spread pheromones around, the gland is ejected outwards. Some male moths own a gland really impressive in size.

Another work* on sex pheromones of Arctiidae moths Creatonotos transiens and Creatonotos gangis says: “coremata are huge, pneumatically eversible organs composed of two pairs of tubes, up to 37 mm long, each covered by ca. 3000 scent hairs (scales).”

Coremata can be even longer than the moth body and of different shapes, from a small ball to a long tube. Whilst hair help to spread pheromones around to attract females, males also wave their wings for a bigger covering. Curious that males hit females' heads with this very coremata. Well.

This organ is pumped up with blood or air. The pic above features a dead moth male which coremata gets pumped up with air from a pipette applied to a cavity in a moth body. Alive males pump up coremata with air intaking through the abdomen.

After a successful interconnection with a female that responsed to a pheromone call is done, coremata gets smaller in size whilst penis gets bigger. Still that's not the end of the story. Male has to hold female long enough to finish the mating process. Doesn't seem quite a sinecure.

If you happen to be entomologist, now it's time for doctor games. Study of the lepidoptera genitalia is of such great importance that there are plenty of tools today created only for that routine. And the most crucial parts are evidently hidden inside of an insect body... due to that very size loss. It can be rather tough to spread male genitalia as properly to examine essential elements.

However, some brainy Australian guys created this pump device for increasing insect genitalia. “The Phalloblaster inflates the genitalia with a stream of pressurized alcohol to create the same shape as when the insect was alive. The alcohol dehydrates and hardens the structure, so that once the process is over the genitalia remain inflated rather like miniature balloons. It makes them easier to study.”

By the way, phalloblaster is properly called vesica everter. But really, who needs fancy “everter” when you have phalloblaster?

Few more words about males and penises. Females of some species choose males by quantity of pheromones, body size and (!) coremata size. Many of males with coremata once were distasteful larvae due to alkaloids which they got of leaves of some toxic plants in the feeding stage. These alkaloids kept as well in imago body.

The quantity of alkaloids gained in the feeding larval stage corresponds with coremata size of an adult male as well as the quantity of pheromones produced, so more toxic males get a higher sexual rank that their average, not as toxic comrades. Part of the toxins are later transferred with a male sperm to a female during mating process and to ova which female lays later, for protection her and the offspring from predators. Naturally, females prefer males with a bigger coremata.

For those who have further interest in the interconnection between larval taste preferences, male attractiveness and female reaction, this book will be helpful: For Love of Insects by Thomas Eisner, father of chemical ecology, http://www.hup.harvard.edu/catalog.php?isbn=9780674018273. Another his book Secret Weapons tells how Utetheisa ornatrix uses toxins to deter off spiders and attract a mate: http://www.hup.harvard.edu/catalog.php?isbn=9780674024038&content=reviews.

Video to the book Secret Weapons:

*Sex pheromones of two Asian moths (Creatonotos transiens, C. gangis; Lepidoptera--Arctiidae): behavior, morphology, chemistry and electrophysiology. Wunderer H, Hansen K, Bell TW, Schneider D, Meinwald J.: http://www.ncbi.nlm.nih.gov/pubmed/3817109.

Coremata in beautiful macro pics and terminology: http://lepcourse.wikispaces.com/file/view/sex+scales.AZ.+aug.12.pdf.

По материалам Wired, http://www.wired.com

Фото: C. nivea, http://blog.zaq.ne.jp/insect/

All the rest posts on: Australia, Asia, curiosity, science, insect preparation, technology, reading, Japan