Sunday, August 21, 2016

The vexation of a vexillologist...

Isn't it great when you get to learn something new. I recently found out what a vexillologist is!

But I am already getting ahead of myself, let me backtrack a little.

I am always upfront about the fact that I am not an expert on insects and bugs. Far from it, I am merely an amateur with an interest and inquisitive nature. It's true that over time you are able to accumulate (and hopefully store) facts and figures about some of the bugs you might encounter on a regular basis, but even so, there is always more to learn and somebody who already has a superior knowledge.

Having said all that, there is always research and I try to use that tool whenever I find myself lacking, which is usually more often than I would wish.

Here's an example: the Large White, or Cabbage White Butterfly (Pieris brassicae). It was whilst researching the parasites of  this species that I stumbled upon Dr Tom Williamson and his excellent blog post entitled: Cotesia glomerata: an amazing example of what evolution is capable of. Dr Williamson describes himself amongst other things as an amateur vexillologist.

I had to look it up in the dictionary to satisfy my curiosity. Just in case you don't know either, I will share in a little while, but first, back to the butterfly caterpillars and their parasites......



A Large White Larva
When I recently witnessed a greenhouse full of these larvae, I assumed that there would be some that had been invaded by a parasitic wasp; I also assumed that it would probably be Trichogramma brassicae. But here is where my knowledge of such things was found wanting. It seems that T.brassicae infects the eggs of the butterfly, rather than the larvae. 



Just before I move on to the real culprit, there is a fascinating story attached to the Trichogramma wasp, that I will try to abridge, as I am sure you have better things to do than spend all day on my little blog.

When the male Pieris brassicae mates with a female, he tries to ensure that she will not then go on to mate with other males. One trick is to transfer pheromones that act as anti-aphrodisiacs, in itself a marvel of nature. But even that can be 'out-natured' by the fact that the very same pheromone is known to attract female T.brassicae wasps. Once the female wasp finds her targeted, and now pregnant butterfly, she  hitches a ride on her, and as soon as she lays her eggs, the wasp gets off and injects her own eggs into the butterfly’s eggs.

Meanwhile, the real miscreant is Cotesia glomerata. Miscreant is possibly a tad defamatory on reflection though? After all this is nature and a natural behaviour, no matter how bizarre or deviant we consider it to be. 

The Cotesia glomerata narrative is every bit as fascinating as the previous contender, as I discovered, and you are about to: assuming you don't already know that is...

Dozens of wasp larvae emerging from the stricken, but still living caterpillar


You see the cabbage (and other) plants that host the caterpillars are fighting back! There is a kind of co-evolutionary race betwixt the caterpillar and the plant: as the caterpillar evolves better ways to feed, the plant evolves better ways to defend itself, so the caterpillar evolves ways to counter etc...etc. 



The parasitised caterpillar protecting the wasp larvae

As the plant reacts to chemicals produced by the larvae, it begins to produce chemical elements that act as an indirect defense by attracting the female C. glomerata wasp, in the same way that the pheromones of T.brassicae do. This wasp is a rather devious parasitoid that finds the  youngest caterpillars feeding on the more nutritious top leaves.This means that the caterpillar will be a better living larder for the young. She will then lay 2 or 3 dozen eggs inside each caterpillar. To return to Dr Williamson's words.."I find this species to be an incredible example of evolution at work. Not only does the larvae of the wasp feed off of the caterpillar host, but after they bite their way out and make cocoons, the host caterpillar spins it’s own cocoon over the larvae, and protects them until it starves to death! Yes, it could be considered pretty gruesome, but fascinating nonetheless."  (© 2016 The Skeptic Canary)


Here is a little video I took of the emerging wasp larvae... 

Note: These vids are too large to show in the email version of my blog. Hence you will need to view the blog directly online.




And at the end of all that, what did I discover a vexillologist to be? Quote: Vexillology is the scientific study of the history, symbolism and usage of flags or, by extension, any interest in flags in general. The word is a synthesis of the Latin word vexillum ("flag") and the Greek suffix -logia ("study.")