0TTE 9815919 The goal of this proposal is to assess the effect of the ant, Pheidole megacephala (the big-headed ant) which has been introduced into Hawaii from Africa and now appears to threaten the diversity of crickets and other insects directly, and other components of the fauna indirectly (crickets are a major component of bird diet). Although the exact date of introduction remains uncertain; reports suggests the presence of this ant early in the century and its particularly devastating effect on arthropods. Evidence of ant predation is still indirect, but it is strong. Recent observations on the prevalence of crickets (October 1997 and January 1998) indicate a sudden and severe reduction of crickets in formerly rich areas. The baseline data upon which this pessimistic assessment is based was collected over a 19 year period. Otte studied the biogeography and systematics of crickets on all Hawaiian Island, collected at 644 geographic points, recorded more than 11,000 cricket songs, and described approximately 190 new species. Over a 9 year period Shaw has researched the phylogeny, species boundaries and behavior of the genus Laupola, with the goal of understanding how new species arise in this island laboratory. During that time she visited many of the cricket rich areas described by Otte (1994). In October 1997 areas previously having huge cricket populations were found to have virtually no crickets at all. Examination of the habitat revealed large numbers of big-headed ants. Observations were conducted again in January 1998 at which time no crickets were heard. Otte recorded crickets at 207 sites on the Island of Kauai. The majority of these sites included members of the genus Laupala. October and January surveys included only one long transect. The goal of this proposal is to assess the impact of ants at a number of lowland and highland habitats. The effect of El Nino must be kept in mind. Because an earlier El Nino in the 1980's had no visible effect on crickets (d espite considerable drought ) the current population decline may not be weather related. The effect of introduced plants must also be kept in mind. The presence of certain weedy plants in the affected transect is noticeable. but, because crickets are not host specific on plants and survive in areas with a high density of exotic plants, vegetational changes are not the likely cause of populations crashes. The possibility that a natural predator-prey cycle is occurring must be considered. Since the ants have been present in Hawaii for over 90 years, the current surge is baffling. Is this classical predator prey cycle? Have these areas been invaded by ants in the past? Will there be any populations crash and subsequent revival of crickets? The possibility that ants will exterminate cricket species is a high possibility. Surveys in Tahiti show that there is now no upland cricket fauna on Moorea-an area known to have had an endemic fauna in the past. Introduced ants are so abundant that the setting of cricket traps is impossible-baits are removed by ants within minutes of setting. The current distribution of six species of Laupala will be determined and compared to baseline data from past studies. Population levels will be assessed and correlated with presence or absence of ants. Crickets and ant colonies will be established at Harvard and Rutgers Universities to assess the effect of ants on crickets in various developmental stages. Cricket colonies will also be kept in several laboratories until the fate of field populations can be assessed.
