The Essex Naturalist
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do not feed. During mating, the males crawls under the female and deposits a
spermatophore on the female genitalia after a few minutes. He then disengages
and wanders away. The female now walks forwards, spreads her legs and curls
her abdomen beneath her and then eats the spermatophore which is held
vertically on the genitalia. Egg laying commences within a few hours and eggs
are deposited as a single mass of between 300 and 900 eggs on leaves, stones or
other objects by the waterside. In spite of the aquatic nature of the larva,
pupation always takes place on land, often some distance from the water, the
mature larvae burying itself in soft soil.
In Essex, we have to date only recorded the commonest species - Sialis lutaria,
though there is no reason why one or both of the others should not also be
present. An additional species, Sialis morio may be overlooked in Britain; it
resembles S. lutaria very closely.
Neuroptera
World-wide, this group contains around 4,500 species, arranged into sixteen
families of which eleven are represented in Europe - six of these in Britain and
five in Essex.
The Coniopterygidae are the smallest of the lacewings; they resemble the
white-fly pests of green-houses and indoor plants and are often referred to as
wax-flies because of their covering of a wax-like substance. We have seven of
the eleven known British species in Essex but this is a very under-recorded group
and at least three additional species, Coniopteryx lentiae, C. pygmaea and
Parasemidalis fuscipennis are quite likely to be here undetected. World-wide there
are about 430 species. Most records herald from light traps and lepidopterists are
particularly urged to look out for them during field trips. The larvae feed almost
exclusively on aphids or scale-insects, each species having its own specific prey
species; in common with other Neuroptera, the Coniopterygidae feed by sucking
internal fluids from the prey. The white eggs, measuring 0.2 - 0.5 millimetres in
diameter, are laid single on the host plant of the prey species. There are three
larval instars as is the norm for Neuroptera. At maturity, the final instar larva
spins a flat silk cocoon which closely resemble the egg raft of some spiders and so
is frequently overlooked. A pre-pupa then forms in the cocoon. The progeny of
the first generation of adult wax-flies have a very short pre-pupal stage, a full
pupa soon forming to give rise to the second generation of adults. However,
autumn forming pre-pupae will not pupate until the following spring.
The Sisyridae, or sponge-flies, are represented in Essex only by the
commonest of the three British species. Sisyra fuscata is an internal parasite on
freshwater sponges and is common throughout the county. In spite of their small
size, sisyrids evolved from osmylid stock (see next species), developing longer
and slimmer jaws and abdominal tracheal gills, losing their labial palpi and
fusing the two tarsal claws into one. Eggs are laid in hatches on leaves, walls,
trees or other objects, usually in crevices and always over water. After 10 - 14