West Virgina White

Chew, Francie Frances.Chew at tufts.edu
Tue Apr 5 13:25:37 EDT 2011


Dear Dave,

I concur with what Harry Pavulaan has written, based on rearing studies
from Massachusetts over many years. Also I don't know where near
Hartford the WVW is in abundance. Harry's observations about Pieris
rapae coming into forest areas where garlic mustard is abundant are very
interesting. I can guess this might actually be a good refuge for P.
rapae to escape the parasitoid Cotesia rubecula, which is a specialist
parasitoid wasp on P. rapae, which does not generally go into the wooded
areas.

On Harry's point about potential hybrids, I have a record for hybrid
mating between a female WVW and a male mustard white (P. napi oleracea),
which yielded eggs, but none hatched. I suspect, based on DNA studies
that Ward Watt and I have done, that the cabbage white is even more
distantly related to WVW than the mustard white, and I would not expect
hybrid matings to be fertile between this species pair.  So the
intermediate appearance of some individual WVW (which can be a highly
variable looking species) might be due to some other causes. There is
good evidence that some (not a majority) of mustard white maternal lines
do fairly well on garlic mustard, as do many (if not all) of their
European counterpart species.

The WVW can be reared in colony, and you can select fairly easily for a
colony of continuously breeding butterflies that don't go into diapause
if reared under long-day versus natural light regimes.

All of the above is published and I can supply you with pdfs if you =
want.

But it is a *great* deal of trouble either way--rearing continuously or
dealing with diapause ( a lot of loss with overwintering diapause
pupae).

A potentially worthwhile experimental approach for your students might
be to study the behavior of  small caterpillars, potentially using a
computer-based event logger (available for free download on internet, it
dumps the data into an EXCEL spreadsheet with times), and explore young
caterpillar (before they die) behavior towards garlic mustard and other
potential plants on which adults lay eggs.

I am not sure it would be very easy to do the work in winter; probably
better to honor the wild schedule, but I understand that might not line
up so well with the school year. However, if you got butterflies around
end of April or beginning of May, you could do some egg-laying
preference observations, and then any eggs laid would hatch in 5-6 days,
and probably be dead by a week after that, so there might be a nice
short-time-length (approx. 3 weeks total time) experiment in this. I'd keep the eggs separate from
each female; one of the really interesting and useful-to-discover
questions would be whether there is any evidence for genetic variation
for behavior among the larvae, and maternal parent in this case could
serve as a proxy for genetics. this would advance knowledge in the
direction that Harry suggested earlier.

Good luck with everything! Dave Wagner is a splendid advisor.

best,
Francie Chew
On Apr 2, 2011, at 8:49 AM, David Cappaert wrote:

All:

I sent a message recently explaining that I'm the new greenhouse/butterfly/education person at  magnet school in Hartford. I'll be in CT next week and will hope to add the occasional observation to the list. With Dave Wagner's input, I put together a concept for an investigation. Any input from the list would be welcome:

The problem: The West Virginia White, Pieris virginiensis, is a northeastern US butterfly with caterpillars that feed on a few brasiccaceae host species. A prime host is two-leaved toothwort, Dentaria diphylla. Like many other insect feeding specialists, the WVW uses the secondary chemistry (sinigrin) of this host plant as an ovipositional cue. The butterflies use the same chemical cue to oviposit onto garlic mustard, an invasive exotic species. Because garlic mustard is a poor larval host, this weed becomes a population sink for WVW.

WVW populations are reported to be in decline, at least in part due to the prevalence of garlic mustard, which grows in dense monocultures in typical WVW habitat. We propose to explore this ecological impact on the WVW by comparing adult oviposition choice and larval development on garlic mustard and native host(s).

Investigation: With students at the Mary Hooker School, we could set up fairly simple greenhouse and field experiments to explore insect/host interactions of the WVW. Some possible steps:

  1.
Identify sources of host plants that can be cultivated in the greenhouse. I have not found nurseries that can supply e.g., D. diphylla ... but there may be botanical gardens that could supply samples, or cuttings. Species of Arabis (A. Laevigata is a host) are available. It could be useful to evaluate other possible hosts in the brassicaceae (considering e.g., the hypothesis that meadow species of mustard plants are suitable, but unused because of habitat limitations).
  2.
Find WVW flights when they occur in the Hartford area. The CT lepidoptera mailing list would be a key resource for this.
  3.
In the greenhouse, we would monitor oviposition on plant hosts in an open vivarium, and in forced-choice tests in sleeve cages. Resulting larval growth would be evaluated in terms of stage-specific survival and growth rate.
  4.
Potted plants could be placed into field settings, and natural oviposition recorded.
  5.
Consider developing a culture so that experiments might be done in cold-season months. WVW's have a single brood, and overwinter as pupae. Could we refrigerate/freeze through a diapause period, and force early emergence?

The overall idea here would be to explore an environmentally significant question in such a way that students could help to design and run simple experiments that might be useful to science.

<><><><><><><><><><><>
DAVID CAPPAERT
1112 Olden Rd
Ann Arbor, MI 48103
734-635 7750
cappaert at comcast.net<mailto:cappaert at comcast.net>



________________________________
From: owner-ctleps-l at lists.yale.edu<mailto:owner-ctleps-l at lists.yale.edu> [mailto:owner-ctleps-l at lists.yale.edu] On Behalf Of Cin & Bill Kobak
Sent: Friday, April 01, 2011 7:43 PM
To: butterflypr at comcast.net<mailto:butterflypr at comcast.net>; 'CT Butterfly'
Subject: RE: Eastern-tailed Blue?

More like Happy April Fool's, eh, Mr. Himmelman?

Cin

From: owner-ctleps-l at lists.yale.edu<mailto:owner-ctleps-l at lists.yale.edu> [mailto:owner-ctleps-l at lists.yale.edu] On Behalf Of butterflypr at comcast.net<mailto:butterflypr at comcast.net>
Sent: Friday, April 01, 2011 9:57 AM
To: CT Butterfly
Subject: Re: Eastern-tailed Blue?

I'm guessing that nice patch of blue sky is also the only one in the state today!

Happy April ;-)

Diane

----- Original Message -----
From: "John Himmelman" <jhimmel at comcast.net<mailto:jhimmel at comcast.net>>
To: "CT Butterfly" <ctleps-l at lists.yale.edu<mailto:ctleps-l at lists.yale.edu>>
Sent: Friday, April 1, 2011 9:12:05 AM
Subject: Eastern-tailed Blue?

Just found this ETB on a patch of coltsfoot this morning. Judging from past year's surprises, this very late March/very early April period seems good for catching early records!

John


John Himmelman
jhimmel at comcast.net<mailto:jhimmel at comcast.net>
*************************
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