Larval competition amongst granivorous beetles

Mike Profit m.profit at sun.rhbnc.ac.uk
Thu May 1 10:04:05 EST 1997

Dear All,
  I hope someone can help me, but I've finally drawn a blank...
I'm just finishing a PhD on the population dynamics of stored legume
beetle pests.  I've been thru' the usual joys of PhD research, but I
think I have found a previously undescribed phenomenon regarding larval
strategies amongst granivorous insects.  Unfortunately I cannot think of
a suitable name for the observed behaviour.
The situation is this....
Ovipositing females will select a host (one legume seed) and lay a
single egg (females will generally hyperdisperse their eggs over the
available seeds to minimise larval competition).  The situation was such
that the females could only oviposit on seeds already containing older
larvae.  I expected to find that the younger larvae would exhibit an
extended development period and reduced weight (correlated with reduced
fecundity).  These two factors would have shown that there was a
reduction in fitness for the younger larvae and I didn't know what the
older larvae would exhibit.
As it turns out, there appears to be two strategies exhibited by the
younger larvae to cope with larval competition.  Type a (for the sake of
argument) exhibit a 'normal' development period (i.e. comparable to
control larvae), but emerge from the seed weighing a lot less than
controls.  Type b larvae suffer delayed development (quiescense) until
the older larvae pupate, they then continue their own development.  The
younger larvae then emerge weighing *much* more than the controls.
There is obviously a trade-off going on here, either develop faster, but
have fewer eggs to lay or delay development but have increased
Scientifically speaking this is quite important, I have left out a lot
of the detail, but the problem is I need to call these a and b
strategists something.  I was thinking along the lines of the Red Queen
Theory that used a charcter out of Alice in Wonderland.  Unfortunately
my knowledge of classical literature is not too good...(too much
counting beetle eggs and surfing the net!).  I wondered if anybody out
there has any suggestions.  If I have not explained anything
particularly clearly please get in touch.  Anybody with any ideas that I
use will be duly acknowledged in the Thesis (I'll be submitting in the
next few weeks).
Thanking you profusely in advance (well done for making it this far!!!).
Mike Profit
m.profit at sun.rhbnc.ac.uk
Males are always the lesser of two weevils

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