[NatureNS] bristletail Petrobius comments

Date: Thu, 22 Aug 2013 23:34:43 -0300
From: "Stephen R. Shaw" <srshaw@Dal.Ca>
To: naturens@chebucto.ns.ca
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&gt; &gt;&gt; were Common Wood Nymphs=2C though these were much l
Hi Angus:
West, turn left as you face the sea at Hall's Harbour. (I learned only  
yesterday that 'Captain Hall' supposedly was a real pirate who got  
grounded there for a winter because his ship had become damaged).   
Walk off the west end of the lobster shack's car park (fish & chips  
recommended, coffee not), ignore the first rather dry 1/3 of the arc  
of cliffs ahead -- very low cliffs seem to encourage predator spiders.  
Bristletails usually occupy the first 8 feet above the cliff base,  
around rainwater seepage zones.  Far fewer after the first point, but  
the hanging valley waterfall about 1 km away, round the second point,  
is a nice photo-op though a rugged walk. Like silverfish, bristletails  
seem not to have a fixed number of instars and moult often. Freshly  
moulted individuals have a mixture of black, green, and brown body  
scales, like those on butterfly wings. These render them very well  
camouflaged against the variable rock, until they move.  If you go  
there, try to take a few good close-ups -- my camera and photo skills  
are not too hot.  It is a harsh environment with few species at the  
best of times, but there seem to be no significant predators of  
bristletails there, which may be their ace survival card, considering  
them to be the most primitive extant insect group with no skills  
except a pretty good back-flip.

Never been East at HH and don't know the cliff structure there, but  
bristletails were abundant at Harbourville years ago and are probably  
distributed all along the volcanic rock coast where the cliffs are  
reasonably high. Apart from the presence of small algae on which to  
feed, they can easily find deep cracks in which to survive the winter  
in the 'rotten' volcanic rock, and this also supplies the seepage water.
Andrew Hebda reported them also from Isle Haute, and they are present  
in places on the coastline opposite, at the Old Wife (5 Is park),  
Wasson Bluff, Partridge Island, and Cap d'Or.

Harbourville is more risky from the POV of getting completely cut off.
You probably know to check tide times at

http://www.waterlevels.gc.ca/eng

Pick Baxter Harbour as nearest to HH, though high/low tide times don't  
vary by many minutes difference all along that coast.

All the best -- let me know if you go and take any photos.
Steve
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Quoting Angus MacLean <cold_mac@hotmail.com>:

> Hi Steve:
>
> Yes, that is the feature that separates the two. I like to think of  
> it as an arrow leading from the black thorax patch towards the  
> abdomen. The same arrow identifies Bombus impatiens by the way,  
> along with the number of tergites covered by pile but the latter can  
> be ambiguous.
>
> Where are the bristletails found at HH? Both East or West?
>
> Cheers, Angus


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