Two questions for scientists

I have nothing to tell you at the moment. But I do have something to ask you, if you happen to have the scientific knowledge to answer my questions. The first question involves physics and arises from cookery. The second involves entomology and arises solely from my morbid curiosity.

1. The Case of the Catastrophically Collapsing Alioli

A few weeks ago I was cooking for guests. Spanish and Catalan dishes were on the menu, so of course I thought to serve alioli among the starters. If you don't know what this is, it is a garlic mayonnaise; the southern French make something very similar with an almost identical name. Indeed, I was cheating: the recipe I followed was for the Provençal aïoli rather than the Iberian alioli. You will find a recipe (not the one I used) here.

I followed the recipe precisely. I made the stuff in a mixer. This is no shoddy 1970s Soviet mixer either; it is a muscular and aggressive KitchenAid machine from America. I very slowly poured a thin stream of olive oil through the hole at the top. The alioli thickened nicely; so much so that the machine's motor began to struggle audibly. But just as I had poured in almost all the oil the recipe demands, the alioli collapsed. Literally: it fell in on itself, all thickness gone. It had, in the space of a moment, become a liquid only as thick as the oil itself had been.

As a a would-be alioli maker, I was deeply annoyed. (It was only a minor annoyance; the jamón pata negra and olives, not to mention a pretty good manzanilla, kept the beasts peaceful until the second course.) As an objective observer, though, I was fascinated. This was the coolest Strange Food Phenomenon I had seen since that one time I opened a very cold bottle of Coke only to watch it freeze visibly, as though caught in that awful ice storm from The Day After Tomorrow. (In that case, I presume the sudden release of pressure upon opening the bottle was sufficient to make the liquid's temperature drop below freezing.) But as for the collapsing alioli: what food physicist can tell me why this happened?

2. Alien vs. Caterpillar

We've all seen caterpillars that look as though they've been festooned with rice. (If you haven't, look here.)

That's not rice. These caterpillars have been parasitised by braconid wasps. Braconids are koinobiont endoparasitoids. Parasitoids are insects -- mostly wasps; a surprising number of flies; and a few representatives of other groups -- that develop in or on other arthropods, usually other insects (though spiders are often victims as well). Unlike parasites proper, parasitoids almost invariably kill their hosts. The hosts of koinobionts continue to live and develop for a time after parasitisation. (Idiobionts, by contrast, permanently paralyse their victims when the egg is laid.) Endoparasitoids develop inside the bodies of their hosts (ectoparasitoids, obviously, do so on the outside, with a bit stuck into their host for feeding). The aggressive creatures in the Alien series, in other words, are classic koinobiont endoparasitoids, as HCJ Godfray points out in his magisterial Parasitoids.

Now you are no doubt cocking a sceptical brow and thinking, If braconids are endoparasitoids, what's with the rice-like stuff? Well, those are cocoons, and that brings me to my question. Braconids develop inside the caterpillar, drinking its haemolymph ('blood', more or less). They avoid doing fatal damage, because this would be fatal to them as well. When they have done growing as larvae, they emerge through their host's skin (not a pretty sight), spin cocoons and pupate. The caterpillar goes on munching leaves, seemingly none the worse for wear.

It is, though. In fact, it is doomed. When the imagines (adult wasps) are ready to emerge, the caterpillar stops eating, goes off some place quiet so its killers can eclose in peace, and dies shortly thereafter. What bothers me is that I can't for the life of me figure out why.

Some parasitoids, just before emerging, go ahead and devour all the vital organs they have hitherto been careful to spare. So far as I know, though, braconids just drink haemolymph. And at the time they stop doing so, their host is still healthy, at least to outward appearance. I am not aware that the wasps continue to feed while in pupal form. I could understand that, when they have opened their cocoons and flown off, the holes from which they exited the host might be exposed, subjecting the caterpillar to dessication or infection -- but from that I'd expect a death rate that, while perhaps high, was not 100%. And yet they always die. Why? What is it that kills them, seeing that the parasitoids' feeding activities themselves apparently do not?