I guess this problem is due to discriminating between parasit and
parasitoid, which is quite an artificial discrimination. We don't have
these two categories in german, only parasits.
Take parasitoid hymenopterans or bacillus thurigensis or ... They
cannot only afford to be virulent, they need to be virulent <lethal>
or they will not survive. Many facultative parasits can easily afford
to be virulent, because they treat the host like substrat for growing
and it doesn't matter, wether it's alive.
I think the parasit who depends on a living host is a special case of
the more general. And good lesson I learned some years ago, when I
just couldn't bring structure into a problem was:
Never give own categories to special or extreme cases!
Lethality is an extreme of virulence, not qualitatively different from
Joachim <joaccigh at w350.zrz.zrz.tu-berlin.de>