Insects & other Arthropods David A Kendall   BSc PhD
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Hover-flies & Lacewings

Class: Insecta
Order: Diptera & Neuroptera

The young stages (larvae) of many hover-flies and lacewings feed
mainly on aphids, and together with ladybirds are among our chief
allies in controlling injurious garden and crop pests . . . . . .

A typical adult Hover-fly (Syrphus)
An adult Green Lacewing (Chrysopa)

These flies belong to the family Syrphidae, within the large order of insects called Diptera, and most are easily recognised by their generally bright colours and hovering ability. The adult flies spend much of their life on flowers, feeding on pollen and nectar, and thus play an important role in the pollination of many wild and cultivated plants. However, the adult flies are perhaps best known for their mimicry of various wasps and bees. Although quite harmless, they no doubt get some protection from would be predators, like birds, by copying the bold yellow and black warning colours of their genuine stinging models. An obvious question for most people is how to distinguish between a hover-fly and a wasp or bee? This can prove difficult without some knowledge of insect behaviour and morphology, but perhaps the most obvious difference (if you can get close enough!) is that hover-flies, like all Diptera, have only one pair of wings, whereas wasps and bees have two pairs. Aphid-eating hover-fly larvae are rather flattened, legless and maggot-like. Most are greenish or brownish in colour and well camouflaged, and largely go unnoticed as they crawl over foliage in search of their aphid prey.

Lacewings belong to an order of insects called Neuroptera. The most familiar members of the group are the green lacewings (family Chrysopidae), which often find their way into houses after dark, attracted by room-lights. A typical example of one of these insects is pictured above. The other members of the group are the so called brown lacewings (family Hemerobiidae). These insects are smaller than their green cousins, and the adults have brown or greyish bodies and brownish, often spotted wings. The adults of some lacewings frequently come indoors or seek shelter in outhouses and garden sheds during the autumn, for winter hibernation. All lacewings, both as adults and larvae, prey on aphids and other soft-bodied insects. Lacewing larvae are rather similar in shape to those of ladybirds and, like the latter, have three pairs of well-developed legs. However, most are coloured a sombre brown, mottled with darker spots and markings. The larvae of some species augment this camouflage-colouring by also covering themselves with the dried remains of their prey, so that each one looks like a small mass of debris rather than a living insect. Lacewing larvae have unusual sucking mouthparts, with a pair of extremely long, slender and conspicuous mandibles (or jaws) that curve forward from the front of the head. The mandibles are tubular structures, rather like a pair of hypodermic needles, which are sunk into the victim's body and then used in the manner of 'drinking straws' to suck out the body fluids of the prey.

hoverfly larva
Larval stage of a hover-fly, feeding on aphids
Photo: V.J. Stanek ©
lacewing larva
Larval stage of a lacewing, feeding on aphids
Photo: Wikipedia GNU Free Documentation License

Get to know the larval stages of these beneficial insects by looking on aphid-infested plants during the summer. Recognition is the first step towards their protection and conservation. If you have to use insecticides, remember to choose the more selective and/or less persistent products which minimise harm to beneficial insects.

Order Diptera

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Order Neuroptera

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Copyright © 2010 David Kendall Last revised May 2010