r.d.j.butcher at dundee.ac.uk
Wed Sep 8 04:50:21 EDT 1999
. I have never heard of one that
> acts simply to cripple the adult (since the parasitic larva will eat as much as it
> can and if there were to be leftovers, the mother would have deposited more eggs -
> nothing goes to waste!)
Hmm, alas the last point is not always correct. It is true that
gregariouse parasitoids often lay sufficient eggs so that little host
is left, and so conform to expectations of optimal clutch size if
eggs are less limited than hosts as you suggest, but there are
exceptions. However, this is frequently not the case for solitary
endoparasitoids. Here the first instar larvae fight or competitively
exclude nutrients oxygen etc and so no matter how many eggs are laid,
only one wasp will eclose ("superparasitism"). You can get small
solitary wasps developing in hosts that could easily support 4-8
wasps of that size, but no matter how many eggs are laid, only one
Am i being pedantic? Well perhaps from the point of view of leps-L
(if so apologies), but i think its important as it illustrates
another intriguing aspect, namely why the evolution of solitary from
gregarious behaviour (it has been argued the other way round, which
may be the case but is less convincing) as host nutrition is not
apparently limited...but i guess thats off-topic for this list.
> I do know of some wasps that lay eggs in the newly formed pupae and consume the
> developing butterfly, but all that emerges is a wasp.
Yup, but these pupal parasitoids often treat the pupae as a slab of
meat, as along with the egg(s) the parasitoid normally injects poison
to retard the host metamorphosis and the wasp larvae feed on the
[paralysed / dead host. In these cases should the parastoid fail to
develop, you still get no Lep, so its bad news for the parasitised
lep. Indeed most ectoparasitoids of leps paralise their host, the
wasp larvae hatching on the outside of the alive but paralised host
and eating from inside in. The larvae rarely recovers from the
paralysis so again if the wasp eggs fail to hatch its still death
for the lep.
Same thing happens with
> monarch eggs, some parasites producing up to 10 adults from one monarch egg -
> imagine that!
YUP, egg parasitoids are common and usually gregariouse. They are
small and lay a clutch size according to the host lep egg size (back
to your optimal clutch size to use maximal host nutritional
resources) since they are usually host-egg limited and so need to
maximise their offspring per suitabvle egg found.
Evolutionary and Ecological Entomology Unit,
Department of Biological Sciences,
Dundee, DD1 4HN,
Work Phone:- 01382-344291 (Office), 01382-344756 (Lab).
e-mail:- r.d.j.butcher at dundee.ac.uk
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