Page 29 - ALG Issue 2 2021
P. 29

                                 biodiversity
Thanks for the good larvae
  Most allotment holders recognise the benefits of certain insects such as the pollination services of bees and other species, or the wealth of beetles that help keep pests in check. These are led by the poster bug – the Ladybird, but not so well known are some of the many beneficial insect larvae that are often confused as pests but, in reality, play a valuable role in controlling other common pests. So here we will take a look at six really useful larval groups.
The parasitic or Ichneumon wasp larvae play an invaluable role in protection against caterpillars and other fleshy plant eaters including sawfly larvae and even aphids. The good work of these larvae is a direct consequence of the work of the adult wasp. These parasitic wasps lay their eggs inside the bodies of caterpillars via means of a sharp ovipositor (egg laying tube) but it is the tiny larvae that then carry out the good work for gardeners by consuming the caterpillar from within. The adult wasps are not capable of stinging humans and carryout a small amount of pollination. Indeed, Ichneumons are often sold commercially for release in large greenhouses. One of the best plants for attracting these handy wasps to your plot is the herb dill.
The gracious lacewing, often described as fairy-like due to its translucent veined wings, is another beneficial insect that eats aphids but so do its larvae – often in the thousands. Adult lacewings are found in three main colours; green,
Hoverfly larvae eating aphid © Claudia Watts
blue and brown. As with the ichneumon wasps, a great plant to attract lacewings is dill but so too are a number of other herbs including fennel, coriander and angelica.
The hoverfly, a great mimic of bees and wasps, is one of our best pollinators and worthy of space on our allotments for that alone, but the larvae are predators that consume on average 1,000 aphids throughout the growing process, making them a really useful insect as both pollinator and pest controller. Once more a search for attracting plants throws up the versatile dill along with lemon balm as great attractants for these versatile friends of the gardener.
Next comes that other aphid muncher supreme: the ladybird. Their larvae, which are often mistaken for pests in their grey spikey armour, consume closer to 5,000 aphids during the development process, and often more than 100 in any day. Fennel and the rather less commonly grown tansy are great attractants for ladybirds who lay their eggs amongst the aphids, and then the feasting begins.
The final two great larvae are, like ladybirds, members of the wider beetle family – the rove beetle and ground beetle larvae. The adults of both these beetle groups are great controllers of slugs and other pests but their larvae too are beneficial in the garden. Ground beetle larvae are round, and maggot- like in appearance often with brown
or orange heads. Close inspection will reveal six small legs and impressive jaws. These larvae are generally found under ground and are often confused with chafer grubs and other soil
pests when in fact they are preying on wireworms and smaller slugs helping
Ladybird larvae © Francis Rowland
Groud beetle larvae © Roger Key
  Lacewing larva © Roger Key
    The food we eat, the fish we catch, the birds we see, the flowers we smell and the hum of life we hear, simply would not exist without bugs
to protect our plants. The rove beetle larvae are similar in appearance but flatter more like a centipede; they
will eat virtually any soil dwelling organisms they encounter from slug to leatherjacket.
Remember all these beneficial insects and their larvae are as likely to be harmed by chemicals used to control pests, so make space and safe areas on your plot for these wonderful gardening friends.
Paul Hetherinton, Buglife
Buglife is the only organisation in Europe devoted to the conservation
of all invertebrates. Invertebrates are vitally important to a healthy planet – humans and other life forms could not survive without them. The food we eat, the fish we catch, the birds we see,
the flowers we smell and the hum of life we hear, simply would not exist without bugs. Invertebrates underpin life on earth and without them the world’s ecosystems would collapse. We’re actively working to save Britain’s rarest little animals, everything from bees to beetles, worms to woodlice and jumping spiders to jellyfish.
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