|
Back to Page 1
end of winter
wildlife watching in boscastle
Mikes Nature Notes
Summer insect life
 Whilst casting a glance at my bed of nasturtiums' the other
day I noticed the huge number of caterpillars of the Large white, or
'cabbage white', butterfly busily munching their way through the leaves. I
thought nothing of this un til several days later when I saw them climbing
the walls on route to finding shelter in the eaves to build their cocoons.
However all was not well - surrounding many of them were clusters of bright
yellow blobs. On reading up on this phenomenon I discovered the ghastly
goings-on! They had been killed by an ichneumon fly, a type of parasitic
wasp which commonly attacks caterpillars, often wiping out up to 80% of a
batch!
The female wasp injects up to 150 eggs into the young caterpillar which
has no means of defence. Using its body as a host the grubs grow inside and
feed on the body tissue, eventually emerging to
form their bright yellow cocoons. The host rapidly dies of course.
This is common and widespread behaviour for many species of wasp, each
having remarkable and grisly methods of nurturing their offspring! The
potters wasp (one for Tim!) makes a 'pot' from sand and saliva before
sealing in a paralysed caterpillar with an egg. There is a mason wasp which
makes tunnels in loose mortar to stash its prey. There is one that detects
the tunnel of the alder wood wasp through the bark of a tree and bores a
hole to inject eggs into a larva, however when this egg develops it is
likely to be parasitized by another wasp species (a hyperparasite) in turn!
Amazing stuff - you can't turn your back if you're an insect!
Butterflies
We have been surveying butterflies along the Valency Valley
once again this summer. This year has been a good year for butterflies, and
we have recorded the rare pearl and small pearl-bordered fritillaries once
more. There is a healthy population of the more widespread silver washed
fritillary which is probably the largest British species and can't be missed
despite its rapid flight.
Both here and on the cliffs I have noticed large numbers of the clouded
yellow butterfly this year (dark yellow with black wing tips). This is a
migrant summer species from southern Europe and as such numbers fluctuate
from year to year. In its warm native countries this strong, fast flyer is a
prolific breeder producing up to four broods a year. Occasionally there is a
big influx into Britain when the European population has swollen in
favourable conditions. Eggs are laid in great numbers on clover, lucerne and
trefoils.
Spring migrants will have time to breed in the UK producing a single brood
in the autumn, but none can survive the cold damp November weather.
Moths
Moths are perceived as the rather dull cousins of
butterflies but when you look into them they are equally fascinating. They
are part of the family of insects called Lepidoptera as are butterflies.
This is a Latin word literally meaning 'tile-winged' - obviously a reference
to the scales on the wings. There are about 2500 species recorded in the UK,
but only 900 or so of these are the more commonly studied macro moths which
are larger and more easily identifiable. The rest are micro moths and are
just impossible!
The main difference between moths and butterflies anatomically is the
shape of antennae. Butterflies have 'clubbed' antenna, moths, in the main,
do not. Moths, of course, mostly fly by night and rest in the day. There are
several day fliers - the brightly coloured cinnabar and burnets, the garden
tiger and the humming bird moth are all examples which are prolific towards
the end of summer.
The moth lifecycle is the same as butterflies, but typically adults do not
live as long. Interestingly, though, there are a few species that do not
feed as adults and have no developed mouth parts - their short adult life is
sustained purely from the stored fats and carbohydrates gained as a feeding
larva.
The commonest way of studying moths is to set up a light trap overnight,
which allows you to identify them the following day. You need a special bulb
- one that emits partly UV light called a mercury vapour bulb to work best.
Apparently, the reason moths so readily come to light is linked to the moon
Invasive plants
Ever since the flood, we have been keeping a watchful eye on the
appearance of invasive plants along the valleys. We all know about Japanese
knotweed, and this hasn't emerged as a problem. What have' turned up though,
especially this summer, are large large quantities of Himalayan
Balsam.
This garden escape has found its way into the Valency catchment, and has
begun to spring up all over the place. It spreads prolifically and can soon
take over an area, much like knotweed. It is a tall very fleshy stemmed
plant that likes stream sides and damp grassland. It has a very ornate pink
flower and the ability to fling its seed a great distance once the ripened
seed pods explode - some of you may have seen this filmed on BBC Wildlife
shows!
Because of this we have been pulling up the plant whenever we see it in
the Valley before this occurs! I have seen whole fields of the stuff when
out walking in other parts of the country, where it's obviously not been
managed, so would hate it to get out of control here.
MS
Information by kind permission of The National
Trust
Back to top
| 
