Friday 21 October 2011

The singing lacewings

Adult common green lacewings, Chrysoperla carnea, are starting to search of suitable hibernation places, and they often come inside buildings. This one was inside my office the other day and allowed me to take her portrait. C. carnea was once thought to be a single widespread species but it is now known to be a species complex, an aggregate of morphologically very similar species that often co-exist.  Courtship involves males and females drumming a song on the substrate where they are sitting with their abdomens. The vibrations are detected by organs in their legs. Males and females respond to each other's drumming in a complex duet and only when they sing the same song does the courtship ends in mating. The different species in the complex have different songs, with characteristic drumming frequencies. The figure below illustrates the differences between the six biological species within the C. carnea group that are recognised in Europe.
The drumming songs of European cryptic species of Chrysoperla carnea sensu lato (from Henry et al in
Both C. lucasina (probably the top photo) and C. c. 4 "motorboat" also known as C. c. "sensu stricto" have been found in the U.K. C. lucasina does not change colour in winter, has "pointy wings" and a dark membrane between the sternites and tergites in the abdomen. C. carnea "sensu stricto" has rounded wings, changes colour and does not have the dark membrane. However, individuals that do not fit either of the species are often found in the U.K.
As their distinctive songs are difficult to tell apart for the untrained eye (ear?), and the morphological characters that do differ between the cryptic species are sometimes not apparent or distinctive enough, identification to these lacewings on the field is tricky. 
 C. carnea 4 "motorboat" may change colour prior hibernation (photo from 10 October 2011).
Lacewing larvae, distinctive large jaws and covered on detritus, which often are the shrivelled skins of the aphids she feeds on.

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