10 June 2016

Insect Sex

(I wonder what kind of spam that title will attract)

I have two tales of insect sex, or shall we more poetically call it insect romance, one rather comical, one surprisingly lyrical.

The above couple are Green Dock Beetles. The humble dock plant is their preferred arena for matters of an adult nature, and the resultant offspring, as larvae, spend their childhoods munching holes in the leaves.  However, those with more exotic tastes are turned on by rhubarb, so if your rhubarb leaves change from thumping great umbrellas to fine lacy hankies you know who to blame, and who's been doing what.

During the breeding season the female's abdomen expands with eggs, and she becomes a more voluptuous form of her normal self.  (Notice the Latin binomial name, Gastrophysa viridula, says something about 'green belly') Luckily for her the male likes something to grab hold off and is quite happy to expend his efforts on the larger lady.

The eggs are laid on the underside of the leaf. In less than a week they hatch into larvae. There are three instar phases (with presumably this flashy badger version below being the last) then they drop to the ground and pupate. For about a week they turn to mush, reform and finally emerge to start the whole cycle over again.

Green Dock Beetle sex may have the aura of a seaside postcard, but that of the Tephritis neesii fly(poor things don't seem to have a common name) is more highbrow, more balletic.
The other day I spotted these two tiny flies dancing delicately on the leaf of an ox-eye daisy in Garden65.
The dance involved waving each wing separately in a sweeping arc over the back. It somehow reminded me of the dying swan in the Swan Lake ballet. An eloquent expression of exquisite emotion.

Isn't it amazing? It went on for over half an hour. Makes you wonder why a small and insignificant creature would go to such lengths to attract a mate. Don't insects just jump on (or present rump to) the nearest insect of the opposite sex? Seems not.

The more you think about it the more you go down the rabbit hole of questioning our significance in the natural world. We think we are the only sentient beings, but anyone who has a pet knows that is probably not true. Watching these tiny creatures communicating with each other with such focus and dedication brought up thoughts about the dimensions and depth of the universe. Indeed the musings got quite mathematical.  We assume our the scale of our world is the true measure of things, but what if the insect world is the baseline, and the reality we inhabit is just one larger distortion?

Quod est inferius est sicut quod est superius

One last thought: the little fly dance also reminded me of a fan dance. So perhaps their courtship rituals are just as earthy as the Green Dock Beetle's.

The following section is not as racy as the previous. It's a bit geeky to be honest. So if you only here for the sex you don't have to read any further. I'd quite understand.

The nameless dancing flies are just as picky as the big bellied green beetles when it comes to choosing plants to lay their eggs on.  These guys prefer ox-eye daisies, or at a push other daisy-like plants in the Asteraceae family.  In this case it's not the leaves that interest them, but the unopened flower buds.

At this point we go down into the world of the miniscule. When hatched the larvae mine into the bottom part of the flower where the petals and stamens and bits and pieces are developing, preventing the proper form of the flower from growing. The adults also eat the seeds before they get blown away.

Lets have a think about that. What are the particular nutrients they need for growth that exist only there in that small space that cannot be found on any other part of this plant, or flower of any other species? Or is the issue more about an evolutionary niche that the nameless flies have managed to find where there is no competition from other insects?  Dunno.

So I went back to the patch where I'd originally seen the dancing flies.

Has this flowerhead with little stumpy ray florets been visited by our friends?

This is it cut open:

Maybe those black bits are signs of munching.

But wait .... what's that little insect lying prostrate on the paper, victim of my hacking?

We'll take a closer look

Doesn't look like a larvae. Maybe he's an even tinier fly.

And so we come full circle - everyone is at it. Wherever you look creatures are mating, hatching, having awkward adolescences, eating, and dancing some more.