Species-specific preferences for the cavity dimensions.

The cavity dimensions were measured as nest length (length of the nest from the base to the plug) and nest width (cavity width), and they were compared with the gall length (Gall:nest length ratio) and width (Gall:nest width ratio). The measures are expressed as means ± SD (range) for N≥3; for lower N, individual measurements are indicated. Note that particularly the P. fabricii nests extend often out of the cavity and their upper parts may be surrounded by dry leaves only, thus the nests could sometimes be longer than the galls in which they are located. For species with N≥10, the Pearson's correlation coefficients were calculated in order to correlate the nest length and width with the gall length and width, with the number of mature larvae contained within the nests and with the gall:nest length and width ratios.