Insect Friends and Foes A Talk by Martin Harvey 20th April
Martin Harvey is exceptionally
knowledgeable about insects and other invertebrates. In this talk
he informed us about the members from these groups of creatures
which may be found in our gard ens .
Martin told us about some surveys which have been carried out in
urban gardens to help discover the ecological importance of ordinary
gardens. Jennifer Owen has surveyed her own suburban garden in the
Leicester area. She does not use pesticides and grows nothing unusual..
She identified around 1700species in her garden. This included a
third of Britain's butterfly species, a half of the hoverflies and
11% of the native plant species. In Sheffield another survey has
looked at 60-70 gardens to try to understand the bio diversity that
occurs in these areas.
Gardens are 1.8% of Britain's land area. They provide trees, ponds
and nest boxes for our wildlife. Rural as well as urban gardens
prove to significant in providing homes and food for a variety of
creatures. Some rarities may be found in gardens. Purple Emperor
butterflies have been seen in local gardens and Martin has recorded
a rare weevil in his garden in Kimble. It appears in May, it has
a long snout and has long orange legs. If seen, tell Martin please.
Garden Tiger moths used to prosper in our gardens, feeding on dock
and plantains but they have undergone a considerable decline.. Stag
Beetles prosper in association with urban gardens breeding in dead
wood which is in contact with the ground
Some of our insect friends in the garden are those which help decompose
dead vegetable and animal matter. The most easily identi f iable
of these is the wood louse of which there are 8 different species.
The Sheffield survey found that very small insects called Springtails
were the most numerous and these are important during the final
stages in the decomposition of vegetable matter.
All insects in the garden are important even if they are only part
of the food chain. Of the herbivorous insects, caterpillars of moths
and butterflies or shield bugs, few are a problem and they add to
the diversity within our gardens and attract other creatures as
well. Martin suggested that within most gardens it would be easy
to see over a hundred moth species within a year.
There are further invertebrates which act as predators , maintaining
an ecological balance within the garden keeping the herbivores in
check.There are over 300 species of garden spiders many of them
specialising in the type of prey they hunt. Ground beetle will eat
the larvae and eggs of insects. Other predators will parasitise
the caterpillars of insects by injecting their eggs into the them.
Amongst these are the ichneumon wasps a large family of insects
which are parasitic.
More friendly insects are those which pollinate plants when moving
from one flower to another in order to feed. There are many of these,
honey bees, bumble bees, moths, butterflies and even some beetles
One of our insect enemies in the garden is the vine weevil, the
larvae of which feed on plant roots. This specie has been introduced
from abroad. There are species of hoverflies whose maggots will
feed on bulbs , and wasps may be a dangerous pest if they nest in
or close to the house.
The Harlequin Ladybird, an invasive migrant has become notorious
in recent years. Although it eats aphids and greenfly, it will also
eat the larvae of other species of ladybird as well as those of
butterflies and moths threatening the existence of our native species.
The Large White butterfly can be a pest in the vegetable garden,
where its caterpillars will feast on all sorts of brassica.
Wildlife Gardening Tips
The provision of food and lodging within the garden is important.
Long grass, decaying flowers, a mixture of trees and shrubs, piles
of logs, ponds and compost heaps may all provide insects with sustenance.
Some plants can be kept to benefit specific insects. Crucifers such
as Garlic Mustard, Lady's Smock, and Honesty may provide the larvae
of the Orange Tip butterfly with food, similarly Buckthorn will
attract the Brimstone butterfly for the same reason. Martin referred
to the Sheffield garden project again to say that insect numbers
do not correlate to the size of the garden. The strength of the
garden is its diversity. To help Martin gave us some tips. Do not
keep the garden too tidy, do not dead head flowers immediately,
grow a variety of trees and shrubs, do not use pesticides but squash
pests instead and have a variety of habitats in the garden.
For more information on this subject, Martin referred to some books,
these were :- "Garden Creepy Crawlies" by Michael Chinery,
"Guide to Wildlife Gardening" by Richard Lewington and
"No Nettles Required" and "An Ear to the Ground"
by Ken Thompson. On the Butterfly Conservation website there is
information about "Gardening for Butterflies". Martin
also recommended the "Evolution Megalab" which has fascinating
data about the Banded Snail.
Thanks to Martin for a captivating talk.