Insects in medicine

I woke up this morning with a strange thought in my head - why aren't insects used more often in medicine? Off the top of my head I could only think of one example (for all of you shouting 'leeches!' they are not insects but worms).

No, the example I was thinking of was the use of blow worm maggots to clean up certain wounds as they will eat the dead tissue reducing the likelihood of infection. An example can be seen here though this is absolutely not for the squeamish!

The real question though was not about the mechanical application of insects but about the use of chemicals derived from insects as medicines. I have often heard about medicines derived from plant chemicals (the obvious example is Aspirin (from Willow if you were wondering)) but not any from insects.

A quick internet search shows that there are some examples, but not much with any really solid evidence behind them. Is there a phytocentric approach to medicinal discovery? You certainly hear of pharmaceutical companies utilising botanists to try and find new drugs and indeed indigenous communities complaining of biopiracy but never have I come across talk of anyone considering the massive variety of insect fauna as a source of new medicines.

So, why not?

It's certainly not because of numbers - there are thought to be around 300 thousand species of plant, but at least 1.3 million species of insect. Perhaps its just that the knowledge of the medicinal effects of plants is better and not close to being exhausted that the harder to find (and more likely to run/fly away) insects are not being considered.

Perhaps more likely though is that plants can't run away and therefore need another form of defence against being eaten. It is often the secondary metabolites produced by the plant to reduce herbivory that are used as medicines. Insects probably produce fewer additional chemicals as a defence mechanism, leading to fewer possible opportunities for finding insects with medicinal properties.

Alternatively, maybe it is just too difficult to convince someone who is ill to eat a beetle...