6
The Essex Naturalist
egested. The pupa is naked - without a silk cocoon - and silk glands are absent
from the gut.
Traditionally, a fourth group known as the scorpionflies (Mecoptera) are
regarded as "honorary lacewings". Though they have little in common with
lacewings, they arose from the same evolutionary stock and, in Britain at least,
are represented by only four species (perhaps five, but that will be discussed
later). Today's talk, therefore will include all four of these groups; the
composition of these is presented below:
ORDER MEGALOPTERA - the alder -flies (1 genus: 3 species)
ORDER RAPHIDIOPTERA - the snake-flies (4 genera, 4 species)
ORDER NEUROPTERA - the true lacewings (23 genera, 66 species)
together with
ORDER MECOPTERA - the scorpion flies (2 genera, 4 species)
True lacewings, alder-flies, snake-flies and scorpion flies together thus form a
relatively small portion of the British insect fauna, numbering only 77 species in
total at March 1997.
Fossil History
The oldest known fossils of lacewings are from the Lower Permian in Kansas,
USA. The Neuropteran Permoberotha villosa is present there as are
representatives of both Megalopteran and Raphidiopteran stock. In the Russian
Upper Permian, three extinct families have been found - Permithonidae,
Prohemerobiidae and Palaehemerobiidae. By the time we arrive at the Jurassic
age the Order is well established and evidence now suggests that the Neuroptera
sensu stricto diverged from the Megalopteran/Raphidiopteran stock in the Upper
Carboniferous period. The common ancestor is likely to have diverged from the
Mecoptera at an even earlier stage in the Earth's history. The relationship thus
appears to be as shown in Figure 1.
Identification
All lacewings (except scorpion flies which are actually only distantly related to
the other three groups) hold their wings over their body like a pitched roof or a
tent. This is true in life and almost always in death, the only exceptions being
the very few that die awkwardly in malaise traps or some light traps. Stoneflies
hold their wings overlapped and flat on top of the abdomen in the horizontal
plane. Mayflies (Ephemeroptera) usually hold their wings up like a butterfly and
have two or three "tail streamers"; these appendages are quite absent from
British lacewings (though two very short ones are present in scorpion flies).