Tuesday, 1 February 2011

Nature's lace

It is at this time of the year that we find the occasional lacewing in the house, tucked away in some corner of a room. Small, slender creatures, with soft bodies and finely veined wings, the lacewings are distinctive and not unwelcome visitors. The thin, elongated body is pale in colour, with darker barring touched with reddish-purple – colouring specific to this time of the year. The narrow head balances two large compound eyes, rounded like brassy pinheads and of similar colour. While long antennae extend out from the head, sensitive and ever searching, two pairs of wings are held tent-like over the body, a characteristic shared by a wider group of related species that includes the alderflies and snakeflies.

It is under the microscope that the nature of these insects is most readily appreciated. Only the thick black hairs, which line each of the many wing veins, seem to contradict the delicate, feminine form that underlines the common name of lacewing. Despite their appearance, these are highly effective predators. In their larval form they sport projecting, calliper-like mouthparts with which they seize aphids and other small invertebrates. This preference for aphids makes the lacewing a popular insect with gardeners.  While some of the larvae are narrow of body, matching the adult form, others are squat and cover their body with debris to form a hard protective case. Some of this debris will include the remains of smaller insects, taken as prey, drained of life and then added to the gruesome sculpture on the larva’s back.

Several dozen different species of lacewing are found in Britain, split into two main types. The most familiar of these are the ‘green’ lacewings, often seen in the garden or around the house, early on a summer’s evening. Less familiar are the ‘brown’ lacewings, generally smaller in size and more sombre in appearance. This simple division, based on colour, falls down in the case of the most common ‘green’ lacewing Chrysopa carnea (it has no common name), which changes colour in the winter, replacing soft green with pale brown and reddish-purple overtones. This is the only one of our ‘green’ lacewings to hibernate as an adult, moving into sheltered outbuildings and houses, and so it is almost certainly the only one you will encounter indoors at this time of the year.

All of our lacewings are nocturnal or crepuscular in their habits, and I often see them at lighted windows or around the moth trap. Easily dismissed, because we so rarely give insects a second glance, it is well worth taking a closer look at one with a hand-lens to take in the gauze-like wings or the brassy pinhead compound eyes.

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