Obligatory mutualism between Dalbulus quinquenotatus (Homoptera : Cicadellidae) and attendant ants

Many aphid. (Aphidae) and treehopper (Membracidae) species depend on ants ( Formicidae) for their survival, but few leafhopper (Cicadellidae) species h ave been reported as myrmecophiles. We studied the Mexican species Daibulus quinquenotatus Delong & Nault in the field and greenhouse. In Jalisco, Mex ico, field populations of D, quinquenotatus increased in size when ants wer e present on their. gamagrass (Tripsacum species) hosts. When ants experime ntally were excluded, predatory spiders invaded the gamagrass habitat and e xtinguished D. quinquenotatus populations. Ants also eliminated two nonmyrm ecophilous and potential competitor Dalbulus species from the host-plant mi crohabitat of D. quinquenotatus. Greenhouse populations of D. quinquenotatu s killed gamagrass hosts in the absence of predators and attendant ants. An ts (Formica subsericea Say) on gamagrass regulated, captive leafhopper popu lations by removing nymphs and adults, and kept le;lf surfaces free from co ntaminating honeydew. Ants also protected leafhoppers from experimentally i ntroduced nabid predators; in the absence of ants, nabids eliminated leafho pper populations. Diet influenced the response of ants to populations of D. quinquenotatus. When ants were denied food, they preyed. upon and extingui shed greenhouse populations of D. quinquenotatus, but when supplied with pr ey (dead eastern yellowjackets), large numbers of ants attended leafhopper populations that grew in size, Few ants attended leafhoppers if they were s upplied with pre); and honey. Our data strongly suggest that D quinquenotat us is an obligatory myrmecophile.