the truth about Hamadryas (Re: Crackers)

[Jeff Crolla/Martha Hancock]

Doug, if you're taking my post as evidence that people in the US read Scott
more than journals, let me point out that I live in Canada and have never
seen a Cracker in my life. I was simply trying to provide some info to
someone whose question went unanswered. I'm aware though that there are
problems with some aspects of Scott's book - taxonomy for one (and I do read
scientific journals). Thanks for setting the matter straight. I had always
assumed that the sound was associated with the wings since it occurs in
flight, and Scott's explanation was a surprise to me too.

all the best
Jeff
----- Original Message -----
From: "Doug Yanega" <dyanega at pop.ucr.edu>
To: <LEPS-L at lists.yale.edu>
Sent: Monday, March 26, 2001 12:40 PM
Subject: the truth about Hamadryas (Re: Crackers)


> >from The Butterflies of North America by James A. Scott, Stanford
> >University Press, Stanford, California, 1986 (there is info on 8 species
> >of Cracker - may be in a local library)
> >under Gray Cracker (Hamadryas februa): "Hamadryas adults land upside down
> >with the barklike wings flattened against tree trunks for camouflage. To
> >await females, males perch on trees and dart out at passing butterflies,
> >insects, even people, often making a "cracking" sound with the abdomen.
> >Males of all Hamadryas species - except perhaps H. atlantis and H.
> >iphthime, which are poorly studied - share this behaviour, which males
> >evidently use to discriminate males from females (males may pursue only
> >non-cracking adults), and which accounts for their common name. Hamdryas
> >males have two long lateral spiny rods extending backward from abdomen
> >segment 8, which probably produce the cracking sound when the valvae
twang
> >the rods (using a spiny dorsal part of the valva; the spiny parts and
rods
> >are longer in species that often crack). The sounds are produced only in
> >flight, for unknown reasons. Both sexes have tympana on the under
forewing
> >base, which S. Swihart proved detect sound but cannot produce it."
>
> James A. Scott is completely wrong, and it's tragic that the nonsense
above
> is in print and will be cited for centuries to come as if it were true. I
> don't know if Scott started it, but he certainly propagated it to many
> people.
>
> REALITY: There are swollen veins on the costal edge of the male forewings,
> and if the males hyperextend during their wing strokes, the wing edges
> strike one another at the top of the upstroke and make a loud "clack". The
> species that do not clack do not have the swollen veins, only males have
> the swellings, and they can only make sounds while in flight. They can
> clack even if the abdominal apex is removed. If you hold a male Hamadryas
> in such a way as to allow it to flap its wings freely, they will clack for
> you, but if you hold a piece if tissue paper vertically above the body so
> it comes between the wings on the upstroke, the clacking is stopped. You
> can turn the clacking sound on and off by raising and lowering the tissue
> from between the wings. I have performed this experiment myself to confirm
> it. The percussive nature of the sound production mechanism has been
> documented in the literature, but evidently more people in the US read
> Scott than read scientific journals.
>
> Argh.
>
>
> Doug Yanega        Dept. of Entomology         Entomology Research Museum
> Univ. of California - Riverside, Riverside, CA 92521
> phone: (909) 787-4315 (standard disclaimer: opinions are mine, not UCR's)
>            http://entmuseum9.ucr.edu/staff/yanega.html
>   "There are some enterprises in which a careful disorderliness
>         is the true method" - Herman Melville, Moby Dick, Chap. 82
>
>
>
>
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