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June 2006
Dear Brownhairstreakers,
Our advertised Brown Hairstreak larval hunt over the Spring Bank holiday
weekend, although not as well attended as we hoped, proved a great success with
seven larvae located and marked which is an excellent start. I know the date was
not the best choice for some and I had a number of apologies from several of our
regulars so a big thank you to Bob Dunnett and Becky Lashley for turning out and
proving so good at finding caterpillars. For a bit of fun, we decided to give
all the larvae names rather than reference numbers so a big welcome to Arthur,
Becky, Colin, Deborah, Eric, Freda, and Gavin. Our colleagues in Butterfly
Conservation Upper Thames branch are clearly far more cultured than we are up
here in the West Midlands and are naming their caterpillars this year after
existential philosophers whoever they might be! Our initial theme was going to
be to honour well known naturalists of Worcestershire but this rather quickly
degenerated into whoever found the caterpillar got to name it, so we finished up
with a rather motley selection. Just in case anyone thinks otherwise, I should
perhaps explain that it is not possible to sex Brown Hairstreak caterpillars and
the alternating male and female names chosen owe more to wanting to avoid any
accusations of sexism than they do to science.
The first three caterpillars were found on the hedgerow leading into the
orchard. Arthur and Colin were both measured at 7mm in length, while Becky came
in at a rather petite 5.5mm. The remaining caterpillars were found along the
main ride within Grafton Wood and ranged in size from just 4mm through to 10mm.
Generally, the larvae were slightly smaller than the ones found at the
corresponding date last year but clearly the season is beginning to catch up.
One thing that we did notice, that we certainly hadn't the previous year, were
several eggs which remained unhatched. They looked perfectly normal with no sign
of disease but for whatever reason the caterpillar had not developed inside the
egg in the normal way.
As is usually the case when looking for Brown Hairstreak larvae, we stumbled
across a number of other insects including various moth caterpillars. Amongst
the more striking were the hairy caterpillars of the Yellowtail moth which can
give you a nasty rash if handled and also the yellow-striped caterpillar of the
Figure of Eight. We also saw several webs of the Spindle Ermine moth.
Finding larvae first time round is one thing, re-finding them as I was reminded
this weekend is quite another. Out of the original seven larvae, I only managed
today to relocate Colin and Deborah. Both had moved some distance from their
original position (in the case of Deborah 3 feet!) but were still on the
original blackthorn. They had both gained 2-3mm in length from the previous
week.
Not sure what to conclude about my failure to re-find the other five. As we
know, the caterpillars are very mobile and may well have been simply missed
because they had wandered off on to adjacent blackthorn. I think this was
particularly likely with the larvae on the orchard hedgerow where the blackthorn
is so intertwined that movement from plant to plant is relatively easy. I also
wondered whether the extreme heat on Saturday had led some larvae to retreat
into the heart of the blackthorn plant. Certainly all of the larvae found were
totally stationery sitting under blackthorn leaves. Some compensation was to
find an additional larva not seen the previous week close to Becky on the
orchard hedgerow and subsequently named Helen (see below).
I will be away next weekend so we urgently need a volunteer to monitor our
growing family of caterpillars. As you will see from the photo, the plant on
which the larva has been recorded is very clearly marked and all labels have
been placed immediately below the position on the blackthorn where the
caterpillar was last seen. I have 10 figure grid references of the exact
locations of the plants and if anyone could commit themselves to taking a look
next week and reporting back I'd be very grateful. Please get in touch.
Mike Williams,
Brown Hairstreak Species Champion