DIURNAL SONG ACTIVITY OF GRASSLAND ORTHOPTERA

For quantitative auditory determination of grasshopper population size s, the diurnal song activity pattern must be known. This activity was quantified for 14 grassland species under optimal weather conditions. Six different patterns were observed: (1) some species sang almost the whole day with a rather constant rate. (2) others increased activity towards noon followed by a decrease in the afternoon, the increase and decrease being rather symmetrical. (3) a third form showed a rapid in crease in the morning, followed by a slow decrease from noon to the ev ening. (4) another type also showed a rather symmetrical curve with in crease in the morning and decrease in the evening, with, however, a ma rked decrease around noon. The extremes were species which showed song activity (5) only in the morning or (6) from the evening into the nig ht. The composition of the grasshopper community allows a rather detai led evaluation of grassland biotopes, taking the well-known ecological habitat-binding of the species into account.