Migration of Neuroptera is poorly understood. The following article
appeared in Neuro News in 1995.
not been updated.
NEUROPTERA IN SHETLAND
Shetland is Britain's most northerly land
mass, consisting of an archipelago of 14 inhabited and hundreds of smaller
islands. Most of it lies above 60O N, while the nearest railway
station is in Bergen and the nearest capital city is Oslo. Indeed,
Shetland belonged to Norway for many centuries and a Nordic influence is
still evident. This Nordic influence extends to the insects, especially
As to the Neuroptera (the other orders
covered by the Neuroptera Recording Scheme have not been recorded in
Shetland), our only common species is the ubiquitous Chrysoperla
carnea. I have to admit that I have not systematically collected
records, so the following comments are necessarily generalised. It seems
most likely that carnea only occurs in Shetland as a migrant,
looking at records from the last three years.
In 1992 there were no records in early
summer (despite several records of migrant Lepidoptera), but there was a
reasonable influx from July onwards. These records appeared to follow an
influx of aphids - certainly Nick Riddiford on Fair Isle recorded unusual
numbers of aphids there. At the end of 1992 there were many carnea
seeking hibernation sites indoors at Baltasound on Unst and in peat-stacks
at Gutcher on Yell (A. Gear) and at Eswick on Mainland (T. Rogers).
The only June record I have in recent
years comes from 1993, and I wonder if this was a successfully hibernated
individual following the 1992 influx. As I understand it mild, wet weather
is the least likely to lead to successful hibernation by adult insects
because fungal infections are more likely. Typical Shetland winters are
mild and wet with little snow and lots of rain. The scarcity of spring
records in Shetland suggest overwintering is rarely successful here. The
rest of 1993 was a poor year for insect immigration and the only other
record of carnea I have from that year was on Foula on October (F.
Ratter), presumably a migrant.
In 1994 there was a massive influx of
Lepidoptera and hoverflies (Syrphidae) in early July and several carnea
were recorded at this time. Further Lepidoptera immigration in early
August lead to further carnea records scattered around the islands
and including records from the two remotest localities - Foula (F. Ratter)
and Fair Isle (N. Riddiford). Lacewings continued to be seen through the
autumn with insects again seen indoors at Baltasound at the end of the
year. There was no obvious sign of an aphid invasion in 1994.
In summary, Chrysoperla carnea
appears to be a migrant in Shetland, recorded from July onwards but
usually failing to overwinter. It is also worth recording that hibernating
specimens have included both green and brown forms.
The origins of the migrant carnea
are also open to discussion but I would suspect that Scandinavia is as
likely a source as anywhere. The lacewings of early August 1994 were
associated with an influx of migrant moths that included species most
likely to have originated in Scandinavia. Incidentally, carnea has
been recorded from Faroe, another 300 km north-east of Shetland. There are
11 records of specimens brought to the Faroese Museum of Natural History
in September to November (D. Bloch and H. Mourier, 1994. Pests recorded in
the Faroe Islands, 1986-1992. Fróðskaparrit 41. bók. 1994
Five other species of Neuroptera have been
recorded in Shetland. In the summer of 1889 J.J.F.X. King (1890,
Neuroptera from the Island of Unst Ent. Mon. Mag. 26: 176-180)
recorded Hemerobius simulans, Wesmaelius nervosus and
Wesmaelius subnebulosa at the Halligarth plantation on Unst, as
well as Chrysoperla carnea, of course. W. nervosa was
recorded there again in 1994, as well as at Eswick on Mainland (T.
Rogers). W. subnebulosa was also recently recorded, on Yell in 1990
(B. Laurence). Two further species were recorded at Eswick by Terry Rogers
in July 1994 - Hemerobius humulinus and Hemerobius
What is the status of these species? Well,
there are virtually no native trees left on Shetland and most plantations
have recent, post-war origins. Records of the same species at Halligarth
over 100 years apart might suggest a species is resident there. However, I
have visited the site regularly over the last seven years and I have never
seen anything resembling a brown lacewing before, yet I saw three in 1994,
a good migrant year. The Hemerobius species at Eswick were first
recorded on 5th July 1994. On this day Shetland was smothered in Red
Admirals Vanessa atalanta, Diamond-back Moths Plutella
xylostella, Silver Ys Autographa gamma and the hoverflies
Metasyrphus corollae and Episyrphus balteatus. Terry Rogers is
also adamant that there have never been brown lacewings in his garden
before but in 1994 there were dozens, presumably attracted by an
infestation of aphids on the trees there (aphids which have built up over
recent years rather than arriving in 1994).
Then there is King's record of H.
simulans at Halligarth last century. This species is associated with
conifers, none of which are planted in the Halligarth plantation (or
anywhere else on Unst last century), although there is the possibility of
incorrect determination in this case. King was convinced that the
Neuroptera he found had been imported with the shrubs as he found them
nowhere else on Unst (and presumably simulans' association with
conifers hadn't been established in his day). However, the trees at
Halligarth had been planted for almost 50 years at the time of King's
visit - a long time for a population to survive in a tiny area of habitat
(Halligarth is about 100m x 100m in area). King also noted that the summer
of 1889 was exceptionally fine, conditions which I would associate with
So, are all these species migrants?
Obviously it is too early to say, but as we collect records over the years
a clearer picture may emerge. Now we know what we are looking for we can
search more intensively for brown lacewings during periods without insect
immigration to see whether Shetland has any resident Neuroptera. Certainly
some species may be catholic enough in its tastes to maintain a foothold
in the islands. However, I wonder whether any species recorded could
survive in a group of islands where virtually the only trees are a few
scrawny willows, sycamores and conifers.
Finally, while I have acknowledged
recorders in the text where appropriate, I must add our appreciation of
the efforts of Colin Plant in identifying our specimens and encouraging