We studied an imported host-parasitoid community in Hawaii, asking to
what extent the species covaried in a systematic fashion even though a
ll species were exotic to Hawaii, and occurred in an artificial agro-e
cosystem (a commercial guava, Psidium guajava L., orchard), Using knoc
k-down pyrethrin sprays we were able to accurately quantify numbers of
the host, [oriental fruit fly, Bactrocera dorsalis (Hendel)] and its
four major parasitoid species [Biosteres arisanus (Sonan), Diachasmimo
rpha longicaudata (Ashmead), Psyttalia incisi (Silvestri), and Bi. van
denboschi (Fullaway)] at hourly intervals. We found that the parasitoi
ds' activity and abundance was well correlated with the activity and a
bundance of their host, and that all four parasitoid species covaried
in concert with one another. In fact, the magnitude of correlation bet
ween the different species in this system was greater than the correla
tion with temperature. This shows clearly that an entirely exotic comm
unity, reassembled piecemeal as a result of biocontrol efforts, can en
d up with patterns of temporal covariation that are highly coincident.
One other interesting result concerns the speed with which sprayed tr
ees were recolonized by the fruit fly and its parasitoids. The time th
at it took each species to reach its mean density prior to removal by
the first pyrethrin spray at 0600 hours varied. It took 2 h for female
B. dorsalis to recolonize guava trees to pre-spray levels. It took 3
h for Bi. arisanus, 4 h for D. longicaudata, 7 h for Bi. vandenboschi
and 14 h for P. incisi to reach pre-spray levels. The fact that Bi. ar
isanus recolonized vacant trees almost as rapidly as did the fruit fly
pest suggest that there is little opportunity for the fruit fly to es
cape in space and time by ''staying one step ahead of its enemies''.