Effects of trap design on catches of grassland bibionidae (diptera: nematocera)

Abstract

Bibionid flies were sampled in grassland in Northern Ireland from 4 April to 13 June 1985 using water and sticky traps with a range of characteristics. Nearly 70 000 bibionids were taken, of which 89-5% were males. Bibio johannis (L.) accounted for 96% of the catch, the rest comprising Dilophus febrilis (L.) (3%) and D. femoratus Meigen (1%). Trapping was carried out adjacent to a hedgerow and in the centre of the field. Differences in the abundance of the flies at these two locations occurred for all three species. Yellow was the best colour for maximizing catches. Greater numbers of B. johannis (63%) were taken in water than sticky traps, but over 76% of Dilophus spp. were caught on the latter. Increasing the diameter of water traps tended to enlarge the catch (principally B. johannis), but catch per unit area was relatively constant. The height of sticky traps above the ground affected the catch of all three species, indicating different flight levels.