title: Functional response of Gonatocerus ashmeadi and the "new association" parasitoid G. tuberculifemur attacking eggs of Homalodisca vitripennis.
abstract: The functional response of two egg parasitoids, Gonatocerus tuberculifemur (Ogloblin) and G. ashmeadi Girault (Hymenoptera: Mymaridae), to varying densities of Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs was studied in the laboratory. G. tuberculifemur showed a type II functional response where parasitism increased at a decreasing rate as host egg density increased from 5 to 40, reaching an asymptote of an upper limit of 9.3 host eggs within the 1-h exposure period. The instantaneous attack rate and handling time as estimated by the random predator equation were 2.28/h and 0.10 h, respectively. In contrast, G. ashmeadi showed a type I functional response where the number of hosts attacked followed a constant linear increase regardless of host density to an upper limit of 11.5 host eggs within the 1-h exposure period. Female G. ashmeadi parasitized on average 4.3 and 3.5 more eggs per hour when presented with 10 and 20 H. vitripennis eggs, respectively, compared with G. tuberculifemur. When 5 or 40 H. vitripennis eggs were offered, there was no significant difference in parasitism rates between parasitoid species. Percentage of female offspring was significantly higher (5%) for G. ashmeadi compared with G. tuberculifemur. Under the experimental conditions used in these evaluations, results suggest that G. tuberculifemur is an inferior parasitoid to G. ashmeadi.
authors.affiliation: Department of Entomology, University of California, Riverside, CA 92521, USA. nic.irvin@ucr.edu
authors.forename: Nicola
authors.initials: N
authors.lastname: Irvin
authors.forename: Javier
authors.initials: J
authors.lastname: Suarez-Espinoza
authors.forename: Mark
authors.initials: M
authors.lastname: Hoddle
mesh_terms: D000818:Animals; D005260:Female; D006430:Hemiptera / Q000469:parasitology*; D006790:Host-Parasite Interactions; D008297:Male; D010063:Ovum / Q000469:parasitology*; D010572:Pest Control, Biological; D012744:Sex Ratio; D014863:Wasps / Q000502:physiology*