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  leaf beetles on aroids
From: pjm at gol.com (Peter Matthews) on 2008.05.19 at 18:12:45(17588)
Dear Aroiders,

I am currently in the Philippines (Luzon) looking around for wild taros.

Something I have noticed here is the presence of a large beetle
(irridescent green back, bright orange head) frequently feeding on the
leaves of Colocasia esculenta and very rarely on the naturalised
populations of Xanthosoma sagittifolium, and not at all on the native
Homolomena philippinensis. Nor on bananas or other obvious garden plants.

The beetle is large, about 1.5 - 2 cm long, and cuts a circular line on
the leaf of taro before eating out the central portion, leaving an often
near-perfect circular hole in the leaf. The damage itself is quite
beautiful.

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From: crogers at ecoanalysts.com (Christopher Rogers) on 2008.05.20 at 16:15:41(17594)
Hiyer, Peter!

I would very much like to see you pictures. You called them leaf beetles. Do
you mean that you think they are chrysomelids?

Happy days,

Christopher

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From: botanist at malesiana.com (Peter Boyce) on 2008.05.21 at 00:16:44(17597)

Dear Peter,

These sound to be chrysomelid beetles; they are a common leaf predator (also
inflorescence predator or possibly pollinator) here in Sarawak. Ther
particularly seem to go for Alocasia, Colocasia and Schismatoglottis and
much less often Homalomena (maybe because of the resins) and climbers
(possibly because of the sclereids).

Chris Darling has done some excellent reserach into them.

See attached images from here.

Very best

Peter

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From: eugene_hoh at yahoo.com.au (Eugene Hoh) on 2008.05.21 at 14:11:30(17600)
hi Peter, Christopher & all,

At the International Aroid Symposium in Kuching back
in 2004 (as some of us on aroid-L will remember)
there were some very interesting presentations on
animal-plant interactions - and one of these was,
indeed, a paper on beetles cutting circular holes in
aroids, by entomologist Christopher Darling.

Apparently these cuts allow latex (unpalatable to
beetles?) to drain from the encircled areas, which are
subsequently eaten. Darling's study was conducted in
Vietnam - but during the symposium field trip he
pointed out similar holes occurring in some local
aroids (eg. Alocasia sp. - A. scabriuscula??) which we
saw growing near roadsides and streams. All the holes
seemed to be about the same size.

Here's a link I've found, to a published paper:

http://www.eeb.utoronto.ca/system/files/2007_Darling+_Holey_aroids_Biotropica.pdf

In case the link doesn't work, the reference is:
Biotropica 39(4), 555-558, 2007; and the species
studied were the beetle Aplosonyx ancora
(Chrysomelidae), Alocasia navicularis and Colocasia
gigantea.

The paper also mentions that the Philippines is within
the range of the genus Aplosonyx, and all the recorded
host plants of the genus are aroids (C. esculenta is
one).

Hope this is useful.

cheers
Eugene

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