Enicospilus - Stephens, 1835

National insect week continues!

The japantarra [Central Bearded Dragon - Walpiri] honours this by consuming as many as he possibly can in as short a time as possible. Of course, he does that every week, so it's unlikely that he's actually aware of the event.

Here's one that won't be going down his throat:

Chongwe, Lusaka, Zambia, February 2013. Photographed using Olympus E-420 DSLR, Zuiko 40-150mm lens and 3 KOOD magnifiers.

In Chewa dialects, this - and numerous species both similar and dissimilar - are referred to as Abemberezi (singular form bemberezi), a group of insects of particular benefit to both farmers and scientists; in English - and related languages - these are the Ichneumon wasps.

Their use to farmers is twofold: first, like almost all wasps, the adults are valuable pollinators; second, ichneumon wasps are one of the most diverse groups of parasitoids on land; animals which spend a significant period of their life as a parasite on or within another animal.

This second point is where the ichneumons stand out from other wasps; unlike potter wasps such as Synagris proserpina [link], most ichneumons are rather specific in their choice of baby-food, with any species usually sticking to a particular family, genus or species as a host for their developing larvae.

The upshot of all this is that a farmer having a particular problem with any given insect pest can encourage or introduce a selection of species that are known to preferentially parasitize that species, and, so long as chemical control doesn't wipe out the pest or the parasitoid, their problem will be kept at a manageable level thereafter.

While abemberezi are interesting to scientists in a great many ways, they - along with a diversity of other parasitoids - are of particular value as biological indicators.

You may or may not be aware that the top of the food chain is, in evolutionary terms, a very dangerous place to be. It is. Being fussy at the top of the food chain, although a great way to avoid competitive exclusion, is an even better way to go extinct.

Imagine, if you will, that any healthy population required only eight individuals in that species (which would be very low). If a species is a producer (a plant, algae or various bacteria), it only needs enough resources to be available to support eight individuals. Provided that no competitive exclusion, mass predation or cataclysmic event wipes them out, they'll generally survive.

Now say that a herbivore of about the same size as the plant exists, and it needs a population of, conveniently, eight plants, in order for enough food to support it to be consistently available.

Now we need sixty-four plants, in order to support those eight herbivores.

And those herbivores have a predator, again of similar size and, by a curious coincidence (I like the number eight today), requiring a population of around eight herbivores to eat so that it doesn't eat them faster than they can breed (and yes, this is a laughably low figure). That means we need at least sixty-four herbivores to support our predator, and its seven colleagues, and 512 plants.

We are, of course, assuming that these plants, herbivores and carnivores are the only species around and lack disease and exist in a perfectly stable environment.

In this environment, we could perhaps expect a tertiary consumer, or top predator. Think about eagles preying on falcons, or wolves eating pet dogs. That sort of thing. Anyway, the same rules apply about how many need to be around for him to not eat them too fast.

Anyway, this now gets to 4096 plants that need to be alive and well at any given time.

So now, we introduce the real world.

Populations fluctuate. A surprise abundance of plants due to good rain one year means that the rabbits are healthy enough to have an extra litter and double their numbers. Before fox populations can respond, the rabbits have eaten the plants down to their roots and after the winter, only 130 rabbits have survived.

Bad news for the foxes, only sixteen of whom can survive this famine, although, on a happy note - given how dispersed the foxes are within the environment at this stage - not even the two wolves who might theoretically have managed to survive on this population can forage efficiently, so these surviving foxes do quite well for themselves, and only one wolf makes it through the winter.

Oops. No more wolves. Ever.

This is not a real world example. But it serves its purpose well; no matter how fragile the situation gets in the lower levels, the most dangerous place to be is always the top. This used to apply to business, too, until the British Government started bailing out failing giants at the taxpayers expense...

But I digress.

As a parasitoid is essentially a specialist predator, it is in an extremely fragile position and, although some species may thrive in disturbed environments, a diverse assemblage of parasitoid wasps is usually a good indicator of an intact invertebrate fauna - which itself is an indicator of high-value habitats worthy of protection and/or study.

That has to be the most words it has ever taken anyone to get to the point.

Anyhow, this wasp is a member of the vast genus,

Enicospillus

Stephens, 1835

And as such, probably parasitises a selection of Noctuoid moths (such as, but probably not its actual host, the Erebid Laelia robusta [link]). 

Also, it's somewhat bizarre and alienesque. Here's another picture, to give you more of an idea of its form:

And that, folks, is all.