Spatial distribution of some Neuroptera Planipennia on trees

During 1989 research was carried out in an urban garden. 50 centimetres of trunk, 50 centimetres of branch and 10 leaves were examined on Quercus peduncolata, Corylus avellana and Sambucus nigra. Immature stages of Neuroptera Planipennia were collected belonging to 7 different species. The average density (total no. of specimens/total surface area) of Chrysopidae eggs was about twice as high on leaves as on the bark (trunk and branch). All the specimens on the bark were Mallada. The percentage of parasitization, due to Telenomus chrysopae (Hymenoptera Platygastroidea Scelionidae), just touches 40%. Also for the larvae the average density is slightly higher on the leaves than on the bark. The Mallada larvae were all found on the bark. The percentage of parasitization on the Chrysopidae larvae, was about 15%, and was due to Hymenoptera Chalcidoidea Encyrtidae, Eulophidae and Proctotrupoidea Heloridae. All the cocoons were Conwentzia psociformis and were found on Quercus. The average density is very much higher for the leaves than for the bark. The number of cocoons on the trunk increases as the season progresses. The percentage of parasitization, due to Hymenoptera Ceraphronoidea, reaches altogether 61%. Among the results obtained the most important concerns the Mallada whose eggs and larvae were found almost exclusively on the trunk. Such behaviour can considerably influence the efficiency of the different sampling methods.