Subject: Pieridae at moist earth

From: Kenelm Philip <[email-masked]>
Date: Mon, 29 Jul 1996 12:38:39 -0800

Michael Healy wondered if other Pierids beside _P. napi_ concentrate
on moist earth. In Interior Alaska I have seen large aggregations (hundreds
of individuals) of both _Pieris napi_ (Mustard White) and _Colias palaeno_
(Palaeno Sulphur) on damp earth. Other lepidoptera do this as well:
_Celastrina argiolus_ (Spring Azure) and _Eulype hastata_ (Geometridae)
(Spearmark).
_Pterourus canadensis_ (Northern Tiger Swallowtail) does this as well, but
not normally in such high numbers. _Erebia disa_ (Disa Alpine) is often
seen at roadside seeps along the Dempster Highway.
        Smaller numbers of many other species of butterflies may be seen
feeding at damp earth in northern regions.

                                                        Ken Philip
[email-masked]

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From: [email-masked] (David N. Gaines)
Date: 1 Aug 1996 21:17:44 GMT

In article <[email-masked]>, 
[email-masked] says...
>feeding at damp earth in northern regions.

I have seen this many times with numerous different species in 
different Families (Pieridae, Nymphalidae, Papillionidae).  From what I 
have heard, these butterflies are males and are sucking salts 
(micro-nutrients) from the damp earth adjacent to puddles and along 
stream/river banks.  I have also heard that Pieris males will congregate 
on earth which has been pissed on.  I do not know what exactly they are 
consuming or why it is only males involved???.  Does anybody know???

David

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From: [email-masked] (B Karner)
Date: 2 Aug 1996 19:58:22 GMT

David writes:

: I have seen this many times with numerous different species in 
: different Families (Pieridae, Nymphalidae, Papillionidae).  From what I 
: have heard, these butterflies are males and are sucking salts 
: (micro-nutrients) from the damp earth adjacent to puddles and along 
: stream/river banks.  I have also heard that Pieris males will congregate 
: on earth which has been pissed on.  I do not know what exactly they are 
: consuming or why it is only males involved???.  Does anybody know???

Because the Lepidoptera have tubular sucking mouthparts as adults, they
are generally restricted to the uptake of fluids during this stage.
Therefore nutrients must be present in liquid form or dissolved in an
aqueous medium.  Nectar takes care of any energy requirements (being
"liquid sugar"), however a need for the uptake of metabolic salts still
exists in some species because many larval host plants have been found to
be "mineral poor". It is up to the adult to ensure that the metabolic salt
requirements of the offspring are taken care of.  The most important salt
here is sodium.

Butterflies have been shown to prefer fluids that contain sodium with
respect to other fluids which do not.  But, why only males?  Smedley and
Eisner at Cornell have recently tested the hypothesis that males gather
necessary salts (specifically sodium) and somehow pass them to the female
via the spermatophore.  They found indeed that sodium is passed to the
female and thus to her eggs using _Gluphisia_ moths as test subjects.
They also add that ions such as zinc and phosphorus are also probably
passed from male to female during mating.

I hope my ramblings help:

Brent