Dispersal by Male Doryline Ants in West Africa

Sausage-flies, the giant males of Old World doryline ants, are among the more conspicuous forms of tropical insect life, never failing to intrigue the observer by their numbers, size and bumbling flight. If we follow the conventional classification and include the New World Ecitonini within Dorylinae (cf Brown, 1973; Gotwald, 1977) there is a large literature--on the group’s systematics, biogeography, and behaviour--but little of it quantitative. At Legon, Ghana, 540’ N, a 125 watt ultraviolet light-trap was run; the aim primarily to extend an investigation of seasonality in insects commenced earlier at Tafo, a little to the north (Gibbs and Leston, 1970). However, the facts collected on doryline flights fill a gap in our knowledge and can be viewed in several ecological contexts. Legon was once forested and lies within the ’southern marginal’ forest category of the scheme of Hall and Swaine (1976). It is today an area of derived savanna interspersed with gardens and small plots of food crops but some secondary forest survives about six miles distant. Climatological data for Accra, taken for over 30 years three miles south of Legon, are given in the form of a Leston-Gibbs climograph (Fig. 1) (Leston and Gibbs, 1971). The original data and summary sheets are deposited, together with examples of the species collected, in the British Museum (Nat. Hist.), London. Sudden heavy rain led to the breakdown of the trap on a few occasions: the missing samples were corrected for by dividing the numbers trapped in each 20-day period by the actual total of sampling days and adding this mean (or a multiple of it) to the total. The