Essays on Nature: December 2017

As I write this, the weather has taken a relatively sharp turn as we moved from autumn to winter. The temperature has dived from a relatively mild 15°C to a decidedly chilly 5-6°C. This has the effect of driving many of us indoors, venturing out only when fully wrapped. One insect that also likes to be indoors is the common green lacewing. The lacewing overwinters as an adult (as opposed to hibernating as an egg or caterpillar) and if it can, it will find a way inside your house where it is warm and cosy and safe from predators. Once inside your house, a remarkable change takes place – it goes from bright green to a delicate pink colour. Just why this should happen is unclear – perhaps it is better camouflaged that way despite your choice of décor – but in the spring it will turn back to its natural green colour. In the wild, lacewings hibernate naturally under leaf litter or in other rough and untidy places you may have in your garden, so perhaps pink is less conspicuous in such places.

Common green lacewing - Chrysoperia carnea

When your lacewing leaves your house in spring it will find a mate and very quickly lay a batch of green eggs. The eggs also change colour to grey before the emergence, in a few days, of the lacewing larvae. These are one of nature’s most voracious predators and will eat the larvae and adults of many different species of insect. Aphids are one of their favourite prey insects and they will chomp their way through a greenfly infestation in very short order. When I say chomp, that is not quite accurate as they have no biting mouthparts. Instead, they adopt a similar technique to spiders by injecting their prey with digestive enzymes and sucking out the resultant ‘soup’. Their appetites make them popular with farmers and gardeners who can buy lacewing eggs as a non-chemical pest control. (You can even buy them in batches of 1000 from Amazon!) Once they have cleared your rosebush of greenfly, however, their predatory instincts reduce them to cannibalism until they have eaten enough to spin a cocoon from which the adult insect will emerge. The entire life cycle takes only about 4 weeks, so that there will be several generations produced before the colder weather drives them in search of a warm winter home.

Common green lacewing (Chrysperia carnea) found in our moth trap

If you want to encourage lacewings to your garden – and with an appetite for aphids like theirs why wouldn’t you? – then you can make a ‘hotel’ for them. The ‘hotel’ will be similar to the solitary bee hotels that all the garden centres and supermarkets sell nowadays full of short lengths of bamboo for the bees to nest in. To make one, simply cut the top off a 2 litre plastic bottle (if nothing else it will stop the bottle from ending up in the ocean!), roll up a length of corrugated cardboard and put it inside the bottle so that the ends are protected from rain. Then hang your hotel in the fork of a tree or under the eaves of your shed, pointing downwards so that water can drain out. This may attract ladybirds as well as lacewings, a double blow to next year’s aphids.

Here are a few other species of lacewing proving that they are not all green or all that common.