The biology of Agriotes ustulatus Schaller (Col, Elateridae) .1. Adults and oviposition

Adult behaviour and egg development of Agriotes ustulatus Schaller were studied under field as well as laboratory conditions in north-eastern Italy over a 5-year period. Adults proved to be active in daylight only, particularly in the morning. The flight of A. ustulatus could be well monitored both by sticky traps and sweep net used on Umbelliferae flowers. Light yellow and white sticky traps proved to be significantly more attractive than red and green ones, while black ones showed no effectiveness at all. Sticky trap efficiency was highest when the trap level was lowest and it was not affected by orientation. Adult swarming occurred during a period from late June to early September; most of the specimens (from 68 to 98% of the total amount) were captured in July when the capture peaks were recorded (more frequently in the second half of the month, just after mid-month). The capture level was high only when last instar larvae populations were over 10 larvae/m(2). Sex ratio was about 1.1. Oviposition started 5-7 days after adults had darkened and was completed within 2-4 days. Eggs (0.61 x 0.46 mm) were laid in clusters in the upper layers of the soil. The average number of eggs laid by single females was 75 (SD = 27.9). Embryonic development took 45 days at 15 degrees C, 14.1 at 25 degrees C and 12.6 at 29 degrees C. The hatching percentage ranged between 95 and 100% of the oviposited eggs.