In every garden there are very good reasons for bringing in more insects generally and not just those acknowledged ‘beneficial’. Indeed I would maintain that as well as their aesthetic and educational value almost all insects, including some usually considered pests, are actually beneficial. Obviously some such as the cabbage butterflies can cause serious damage if not controlled but even they may do some good as well.
Pollination is obviously the first benefit from more insects, and more-so as currently the honey bee is absent from many areas. Of course many vegetables, as the food crop, do not require pollination on the other hand most fruits do. Predating & parasitizing other insects is the next well recognised benefit. We have long known ladybirds eat aphids etcetera. But we are only now beginning to understand how ecology works and realising that more different lives in an environment leads to fewer getting out of hand. The more variety of little hungry hunters we can encourage in our gardens the less of a problem any so called pest can ever become.
It can also be seen as the role of some ‘pests’ to be sustenance for other more desirable life-forms as snails become song thrushes. Black aphids withering the tips of sweet cherry trees are feeding up ladybird larvae to pupate then control aphids on other crops nearby. Without other insect eggs, grubs and adults what would small birds live on when they are not eating those on our crops- though it could be argued without them they’d be keener still…
Contribution to fertility is a less obvious benefit but even aphids can be seen as helping here- they do not suck sap, the sap is pushed through them under pressure, they take out some nutrition letting the bulk pass through including much sugar. When this honeydew falls on leaves it’s detrimental as it encourages sooty mould- but when it reaches the soil it encourages many different soil micro-organisms including nitrogen fixing ones. And although nearly invisible almost all living things are continuously depositing bodily wastes adding to the gardens fertility. Then eventually their dead bodies.
Recycling is another huge benefit as without the actions of many small and tiny insects much of our garden surpluses and wastes would be slower to breakdown and return as fertility. Eventually even wood is turned into soil through the action of insects; with wasps scraping the outside for their nests and wood boring larvae inside.
And a hidden benefit is the carbon dioxide. Although we’ve put excess into the atmosphere there is often a temporary shortage in the place where it’s most needed. In still air and bright sunlight carbon dioxide can be completely removed by plants in only a matter of minutes. A multitude of insects breathing out carbon dioxide close up to their leaves are thus giving them a regular supply, regardless of whatever else they are up to.
All together their many tiny actions add up so that a garden that is full of many different insects will be more fertile and productive. And of course far more interesting. And I’d even go so far as to say I find many insects far prettier than flowers.
We already plant flowers for the butterflies and others, make hotels of hollow stems for over-wintering insects and so on. And we can do much more with little effort by simply providing more varied habitats and suitable nest sites. There are many groups to encourage each with their own different needs and benefits. Almost all will be attracted by water and by more flowers in the garden. A pool or pond will bring in and maintain many insects, even a bird bath will help keep them watered. Plants such as lupins and Alchemilla mollis catch dew drops in their leaves saving it for insects to drink. Multiply beneficial are teasels which catch water in their leaf joints, feed many insects with their flowers, the birds with their seeds, and the Mottled Rustic butterfly Caradrina morpheus caterpillar lives on it’s leaves. Also having plenty of ground cover, some long grass, some bare soil, coarse mulched areas, and nooks with lots of dead leaves, perhaps a sandy corner, a damp boggy place and some muddy edges. All these different habitats, even just small ones, will entice a diversity of creatures to move in – and often remarkably quickly.
Encouraging some of the more specific groups-
Bees; apart from taking up bee keeping as such we can also encourage solitary, humble and bumble bees. These are often more effective pollinators in adverse conditions than honey bees. All are best helped by having more plants blooming early in the year such as spring bulbs and flowering redcurrant. Blue and purple and especially large thistle like flowers are very popular with most bees. But they also need nest sites; some like holes in dry ground, bundles of hollow stems, niches in piles of logs or stones, and some need a wall or bank of damp earth such as a ditch side.
Butterflies and moths are always popular but not so of course are their caterpillars, even though some of these are huge and most curious. Many of our most delightful butterflies need particular species to live on as caterpillars, and these may be different to the flowers they later visit. So as well as flowers for the butterflies we also need leaves for the caterpillars. A bank of wildflowers will be a good start and surprisingly some weeds such as docks and thistles are most effective. Brambles are an excellent plant for all stages in their, and most other insect, lives.
Ladybirds and lacewings are well known for their valuable pest control. Along with other insects they need snug places to over-winter and are attracted to bundles of dried corn stems, hollow stems, conifer prunings and so on which can be hidden inside hedges and evergreens. Apparently ladybirds breed especially well on the aphids living on vetches.
Wasps big and small and flies are mixed blessings. Certainly wasps eat an awful lot of other pests as they are carnivorous in the larval stage but later they rob our fruit and annoy us. Some old worn wood is needed for them to make paper for their nests so don’t paint and preserve every last bit. Even house flies have a use as they ensure little corpses don’t simply rot, putrefy and smell. (Under-cover if you make leaves wet flies will clean honeydew and sooty mould off them- buy out of date maggots from the fishing supplier, they will pupate then hatch, and be clean.)
Beetles are generally friends. Some few are pests of crops but most others are recyclers in at least their larval stage and many adults eat the eggs and young of a host of other pests. The violet ground beetles and Devil’s coach-horses are excellent garden predators. Their main need is ground cover especially areas of long grass, and little niches to hide in such as stacks of logs, rough bark on top of mulches and piles of prunings.
Centipedes and millipedes, the first are brownish with legs splayed out the sides, second are black with even more legs arranged vertically. The former are without doubt friends and eat many pests, the latter are on the whole probably pests but still ad to the diversity. Both are encouraged by the same habitats and niches as beetles.
Woodlice and earwigs. I know wood lice are really crustaceans but commonly thought of as insects, and much the same goes for earwigs. Yes these both do some damage but they also eat many smaller pests and I suspect on average these may do more good than harm- if they can be kept away from crops. As with beetles any ground cover and little niches are good encouragement. I find small stacks of bricks, saucers, tiles, slats of wood make good refuges for woodlice. (In some areas these may also attract alien flatworms, these pests consume earthworms and are best destroyed, do not handle them.) Earwigs prefer to hide in hollow stems and in toilet roll tubes stuffed with straw.
Spiders are not strictly insects but every one is a predator. They need little assistance from us outdoors. But under cover we can provide them shady hide-aways in sections of hollow stem, with water nearby in bottle caps, and tie strings or place canes so they make their webs in convenient places.
Dragonflies are far more beautiful than flowers, and they eat mosquitoes from the air and do the same whilst they live in water. Obviously a pool or pond is required, the larvae need to climb out of the water up a stem to emerge as the adult so grow bull-rushes and flags and also have some old rotten logs by the water’s edge as it’s there many lay their eggs.
Water really is the most valuable attraction for bringing in more insects- including mosquitos -do not put goldfish in to eat these if you want any other pond life. Leave mosquito control to the dragonflies, the goldfish soon breed into a shoal and end up eating all the newt and frog eggs as well as everything else.
Likewise there is a bit of a mixed blessing with hedgehogs. Reputed to eat a lot of pests I suspect they eat worms and a great number of beetles as any examination of their dung shows. As worms are useful and beetles are mostly friends it may be encouraging rather than just tolerating hedgehogs is not actually such a good idea…..