The number of insects in the world is mindboggling; some we hardly ever see or notice. However, here are some basic notes on just a few of the insects most often seen in the Garden.
Insects come in three parts (much as Gaul was!): a) the head; b) the thorax, with three pairs of legs; c) the abdomen, plated top and bottom.
The insects go from very primitive, as in the silver fish (found in books), to the advanced, as in butterflies.
Wasps: No need to tell you they are stinging insects, related to bees and ants. They do far more good than evil, destroying large numbers of harmful insects and caterpillars. There are, of course, many kinds, including the social wasp and the solitary. The latter has a narrow strip joining the thorax and abdomen, giving rise to the expression 'wasp waist'!
The social wasps are the papermakers of the world, making it by chewing, with much saliva, a combination of old wood and plant fibres into felt-like masses. Have a look at the layers of an old discarded nest, and marvel at their handiwork - as did the Chinese who got their inspiration for making paper from them. There may be as many as 25,000 wasps in a nest; the long-faced hornets hang their nests from trees and roofs, but the short-faced yellow jackets build theirs in the ground. All die at the onset of winter, except a crop of young queens, who will start laying the worker eggs in early spring; the males only develop in late summer.
The solitary wasps are the masons, carpenters and excavators of the wasp world; one wasp does all the work of building a nest, collecting and paralysing insects, laying an egg on each body, sealing the nest, and flying off for a much needed rest! The hatching larvae have a ready supply of live meat, turning into cocoons and at the end of pupation emerging as a full-grown wasp later in the year or even the following year.
Ants: Their colonies operate on the caste system. Workers have large mouth parts for excavating; soldiers are blind and wingless, with powerful jaws. Reproductive individuals develop wings from special pads, flying off' in search of decaying wood to develop new colonies. These colonies may be tunnels in that decaying wood for the much-feared (by house owners) carpenter ants, or hills of needles, earth and twigs for the common ant.
The carpenter ants are able to absorb nutrients from wood in their digestive tract, thanks to wood-digesting guests residing internally, namely protozoa, which ingest the wood fibres, and bacteria which help with the digestion of nutrients. Other ants feed on honey; some store it against a rainy day by stuffing a few young ants with it till they are too fat to walk around and just hang from the ceiling of the nest - much like the hams in the kitchens of old! Some also keep a group of aphids near their nest as a source of honey dew, 'milking' them by stroking the 'cow' aphids with their antennae; they take great care of their 'herd', moving them to fresh pastures and overwintering them in their nests. Once the new queen has mated, she bites off her wings which are no longer of any use, and then embarks on her egg-laying life, being cared for by the workers, to whom she smells 'good' - Chanel No. 5 perhaps? The queen may live for as long as 10 to 15 years. Ants are responsible for the distribution of many seeds, such as Asarum, Trillium, Hepatica and Cyclamen.
Mosquito: It is the female of the species who bites us; she needs protein for her eggs, but the male just sucks plant juices!
Bees: We hardly need to explain too much about these hardworking insects! The bumbles are the heavyweights of the family, searching nectar in flowers that will bear their weight. Honey bees are sometimes imitated by flies, but they will only have two wings, whereas bees have four. Their hind legs are heavily coated with hairs, arranged to contain balls of pollen, which they collect from one source only at a time, preferring 'complicated' flowers, such as daisies which have many little flowers in a group, thus economizing their time and energy and doing a great job of pollinating. They have been domesticated by man since very early times. Their honeycombs are constructed of beeswax, exuded from the body after consuming honey and pollen; this will be fed, in a variety of consistencies to the grubs, the varying diet differences producing different castes. The Japanese bee (Osmia cornifrons) has been found to be much more active in cold weather than our honey bee and is, therefore, used by orchardists in order to pollinate their fruit trees which may be in blossom when the weather is still cold. It has already been noted that bees have a terrific sense of smell, one hundred times more acute than that of man. And they are able to see the ultraviolet nectar guides on flowers.
Near the water, we find predatory dragonflies that are superb aeronauts! The Green Darner is handsome with a metallic green body and a wingspan of three inches. Their nymph stage is aquatic and may last several years. The 12-spoted Skimmer has a blue-black body with larger wings, each having three brown patches, or spots, and like the Green Darner, spread their wings out in repose. The damselfly is less dramatic, with feeble flight; their golden wings are folded in repose, and they have a forget-me-not blue body.
Spidersare not insects; they are arthropods in the class of arachnids, related to daddy long legs. They are predatory and deaf but have eight eyes in front of the head. Their body has only two parts (insects have three): the thorax which includes the head, having two sets of mandibles, one of them for poisoning prey; and the abdomen, which is full of organs. There are four pairs of legs (insects have three), and each leg has seven joints with tiny claws at the ends. They inject their prey with an enzyme which dissolves the body contents and enables them to suck up the liquid, as they are unable to eat. There are usually three pairs of spinning organs (spinnerets) at the end of the abdomen with tiny tubes leading to the silk glands; the sticky liquid hardens in the air, the spinnerets making separate or combined threads. The spider coats its own legs with an oily substance from its mouth, so that it doesn't get caught in its own web. When the spiderlings emerge from their egg sac and are ready to leave home, which means they've learnt the art of spinning, some do it by 'ballooning', climbing to a high place; they send out a silk thread, wait for the wind to catch it, and, up and off they go, flying through the air, sometimes miles from home. Sounds just the thing for a warm summer's day! Take time to stand and watch a spider at work, and note the shape of her web which may have a dome or orb form. [Hyperlinks added 2013]
Updates to Erica's Notes: Our Garden has been dealing with an infestation of bronze birch borers which love our Himalayan white birches, Betula utilis var. jacquemontii, especially after snow damage in 2009. Some trees have been removed and replaced with a more resistant (but less dramatic) river birch, Betula nigra 'Heritage'. However, other white birches in the Garden seem to be recovering after several years, and further tree removal is not planned at present.
While hopefully not in our Garden, the mountain pine beetle is unfortunately too well known in our province, destroying millions of hectares of pine forests.
European fire ants are becoming a big problem, and some areas of the Garden have been closed to visitors because of them.
Gall wasps have infested the Salix purpurea 'Nana' in the planters by the ramp from the Plaza.
What is an insect hotel? It is a manmade structure made from natural materials that provides shelter and nesting facilities for all manner of beneficial insects. The mason bee condos with which we are familiar would be a good example on a very small scale of an insect hotel.