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Investigations on the flight and flight behaviour of curculionids. Detail investigations were made to determine the flight of curculionids using Moericke- and window-traps in an area in middle Hessia. The results show that the main flight period occurs during May and June, although some species fly during late summer and autumn. During the day, most species fly around noon and in the afternoon; flight before 8 a.m. and after 5 p.m. is rare. Night flight was not detected in any species. During the specific flight period, each species has a certain lower temperature threshold. In these investigations the values were 9° C for Rhynchaenus fagi, 10° C for Apion virens and A. flavipes, 15° C for Phyllobius maculicornis and 20° C for Sitona sulcifrons. At temperatures above 27° C a general decrease in flight activity could be stated. The ratio of ♂♂ to ♀♀ was mostly 1:1. In some species, however, greater differences were noticed though in the cultures there were equal numbers of each sex. Catches in yellow Moericke-traps were nearly four times as great as in blue, green and white ones. Catches in traps at different heights suggested that most curculionids (except Ceutor-hynchinae) flew over legume fields at a height of greater than 1 m.

The relationship between supercooling and survival of the beech leaf mining weevil, Rhynchaenus fagi was examined in exposures at constant temperatures between +10 and −15 °C, and in cycling regimes. Similar observations were made on naturally overwintering field populations. No weevil survived cooling to, or below the supercooling point. The mean supercooling point of weevils exposed to temperatures at, or below +2 °C, or sampled from the field, was consistently below −21 °C. When exposed to a constant +2 or −5 °C, mortality was low, at 10 and 12% after 168 and 126 days respectively. Mortality increased rapidly in weevils exposed to temperatures below −10 °C, with 48% survival after 112 days at −10 °C and only 25% after 84 days at −15 °C. None of the dead weevils had frozen. Periods spent at +2 °C in cycling treatments which included exposure at −10 or −15 °C, extended the duration of survival at the lower temperatures compared to constant exposures at these temperatures, but mortality was still more rapid than at a constant +2 °C. Survival of naturally overwintering insects was consistently high over three winters.

The effect of ambient air pollution with increased ozone concentrations on the feeding behaviour of the beech weevil Rhynchaenus fagi L. was studied. In a dual choice feeding test the beech weevil preferred leaf disks from beech saplings exposed to ambient air against those from filtered air in 65.5% of all cases.

1. Overwintered and starved weevils fed on beech within 5 min of contacting the plant in spring, and oviposition occurred in less than 48 h after feeding. 2. Size of unlaid eggs was significantly reduced when feeding weevils were subsequently starved from beech for 3 days. 3. Date of bud burst did not affect the amounts of feeding or oviposition by weevils. 4. Weevils fed and oviposited preferentially among trees, and the same trees were preferred in two successive years. This preference was independent of bud burst date.

1. In laboratory experiments, R.fagi made feeding holes in eighteen tree and shrub species, including beech, from seven plant families but few plants other than beech were eaten to any extent. 2. Overwintered adult weevils preferred beech to all these eighteen plants in spring. 3. Hawthorn and raspberry were the most acceptable plants if beech was not available at this time. 4. Field collected weevils from hawthorn had partly developed oocytes in early April, prior to beech bud burst. 5. New generation weevils sought alternative food sources in late June and July; raspberry was preferred to the youngest available beech leaves at this time.