The Essex Naturalist
5
THE 1997 PRESIDENTIAL ADDRESS
An introduction to British lacewings (Neuroptera) and their allies
Colin W. Plant
Lacewings are amongst the more familiar and most easily recognised groups of
British insects, though identification to species level can be rather more
problematic. In most European countries they are regarded as having significant
economic importance as natural control agents of aphids and other pests on
crops, though here in Britain we are only just beginning to realise this potential
and the only commercial pest-control use to which they are currently being put
is in the control of aphids on hops Humulus lupulus in some parts of Kent.
So, what is a lacewing? As an English name, the term "lacewing" can, of
course, be applied to as many or as few groups as the entomologist cares to
include. To most people, they are those greenish-coloured insects that
sometimes turn up dead on the window ledge during the winter or spring. But
these represent only a single species of the British lacewings - our only species
which hibernates in the adult stage. There are nineteen such "green lacewings"
currently known in Britain and to these must be added thirty "brown lacewings"
and a few others such as the sponge-flies, wax-flies, the giant lacewing and the
ant-lions. In the past, all of these were regarded as belonging to the sub-Order
Planipennia of the larger Order Neuroptera - a name derived from the Greek
and meaning literally "nerve-wings" or "vein-wings". The term "lacewing"
reflects in English the same meaning. That old Order Neuroptera also included
another suborder, the Megaloptera, into which category were placed the alder-
flies and snake-flies.
Today, however, with the benefit of better knowledge of the evolutionary
relationships between different species of insects and with a far better
understanding of both their life-cycles and ecology, we have arrived at a slightly
modified version of the classification. The term Planipennia has vanished, and
all those true lacewings that it included are now elevated to the Order
Neuroptera. The larvae of these true Neuroptera have suctorial mouthparts
formed from the mandibles and maxillae. The maxillary palpi are absent. The
gut is closed in the anal region and so there is no through passage of digestive
waste products; this is associated with the liquid diet of the larvae and small
amounts of solids ingested are stored in the anterior gut and voided as the first
act of adulthood. Two or more generations per year are normal. The pupa
reposes in a silk cocoon and this silk is spun not from the salivary glands but
from glands in the hind gut beyond the closure and extruded through the anus.
The Megaloptera includes only the alder-flies, whose larvae are aquatic,
whilst the snake-flies are placed in a new Order, the Raphidioptera and have
terrestrial larvae. The larvae of both Megaloptera and Raphidioptera have true
biting mouth parts. The gut is complete and solids ate both ingested and