...
Back
on the Green Isle
by
Pete
Eeles Sat
Jun 15, 2013 8:53 am
I was fortunate to be working in Dublin at the end of last week, and managed to
spend a chunk of time at North Bull Island Nature Reserve, off the coast of
Dublin. I didn't know the place existing until I looked at the sightings page
for the Republic of Ireland (http://www.butterflyireland.com/RECORDS.aspx)
and saw that 298 Marsh Fritillary (f. hibernica) were seen on transect on
7th June. Clearly, there had been a population explosion and so I got in touch
with David Nash (co-author of the excellent "Ireland's Butterflies: A
Review" and also a former President of the esteemed Dublin Naturalists'
Field Club) who gave me some pointers. Despite an unpromising weather forecast,
I was on site at 0930 on Wednesday morning, having landed at Dublin airport at
0815. As I made my way to the favoured spot for Marsh Fritillary I came across
several Garden Tiger moth larvae ("woolly bears") on the paths between
the sand dunes, as well as several Small Heath. I was also on the lookout for
female Common Blue to see if they conformed to the description of ssp.
mariscolore where the female has extensive patches of blue, with large and
bright orange marginal spots. The distribution of this subspecies is a subject
of debate, but the few females I saw were quite "normal" to my eyes.
Common
Blue (female)
I eventually reached an area where masses of Devil's-bit Scabious (the larval
foodplant of the Marsh Fritillary) grew, interspersed by Marsh Orchids. In fact,
I've never seen so much of the stuff; every square metre contained a good number
of plants.
North
Bull Island
Devil's-bit
Scabious
Given my current fascination with subspecies and forms, I was really looking
forward to my first ever sighting of the hibernica form of Marsh
Fritillary, which is found all over Ireland, and is said to have a greater
contrast between the orange ground colour and cream markings than those found in
the south of England that I'm familiar with. Within 30 minutes a minor miracle
happened when the dark clouds that dominated the sky dissipated and the next few
hours were spent in perfect butterflying conditions, of intermittent sunshine.
It wasn't long before I found my first Marsh Fritillary, then another and
another. I must have seen well over 100 by the time I'd left.
Marsh
Fritillary f. hibernica (male)
Marsh
Fritillary f. hibernica (female)
Marsh
Fritillary f. hibernica (male) on Marsh Orchid
Marsh
Fritillary f. hibernica (female) on Marsh Orchid
At 1240 I started to leave the site, having had my fill of Marsh Fritillary
sightings, interspersed by the occasional Common Blue and Small Heath, and
started to wander the mile or so back to the car. I then noticed a female Marsh
Fritillary acting very strange and clearly looking to oviposit. I managed to
capture her on video:
She eventually found a leaf on which to lay and, blow me down, another female
was already tucked away ovipositing on the same leaf. Now I don't know if
this is just pure coincidence, but the chances of the same leaf being used among
the thousands of leaves available must be pretty small. In the first photo below
you can see the pair of ovipositing females toward the bottom centre of the
picture, followed by a closeup and a video.
Pair
of Marsh Fritillary f. hibernica (female) ovipositing
Pair
of Marsh Fritillary f. hibernica (female) ovipositing
As I watched the pair oviposit for quite some time, a third female flew onto the
same leaf before, eventually, landing about a foot away where she found another
leaf on which to oviposit.
Marsh
Fritillary f. hibernica (female) ovipositing
Why 3 females should all choose the same leaf given the area of the site and
amount of larval foodplant available is beyond me, but I do intend to write this
up for a journal, since it's not something I've come across before. Some
theories are:
1. Pure coincidence.
2. The particular plant is in a favoured position for the site, and has a
favoured leaf.
3. The females give off some chemical/pheremonal signal that attracts other
females - perhaps giving the resulting (and larger) larval nest a better chance
of survival (assuming, of course, that there is available larval foodplant).
I didn't have time to wait for all 3 females to finish laying (the process
taking literally hours) so returned the following morning to get some shots of
the various egg masses.
Marsh
Fritillary f. hibernica egg masses 1 and 2
Marsh
Fritillary f. hibernica egg mass 2 (closeup)
Marsh
Fritillary f. hibernica egg mass 3
And finally, for some reason I really like the photo below, so thought I'd
finish this report with it! As usual, an excellent time spent in the Emerald
Isle. I must admit, I love the place - perhaps it's because I'm technically
half-Irish (all of my grandparents on my mother's side came from Ireland)!
Marsh
Fritillary f. hibernica (male)
Peter
Eeles. 15
Jun 2013