Spring Dispersal Flights of Pond-Skaters Gerris spp. (Heteroptera)

Abstract

Dispersing pond-skaters Gerris spp. were trapped in light-reflecting glass traps during the ice free periods of 3 yr at Lake Sagsjon, Sweden. A light-trap was also operated. Catches consisted mainly of G. argentatus Schumm., followed by G. lacustris (L.). Pond-skaters were trapped from late April to the end of May, except for one G. argentatus in late Aug. The seasonal distribution of the catches is due to differences in habitat selection before and after overwintering. In spring, pond-skaters are attracted to and alight on reflective surfaces such as ponds. In late summer they move to the land to overwinter. Pond-skaters were only trapped during daylight; no pond-skater being caught in the light-trap. Catches occurred between 0900 and 1700 h with a peak at noon. The critical lower temperature threshold for flight in G. argentatus seems to be 12-13.degree. C in spring. Pond-skaters trapped during the spring dispersal period had undeveloped ovaries, no food in the gut, and little or no adipose tissue. The species composition of the catches was mainly due to the specific habitat near the traps.