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1 December 2009 Functional Response of Gonatocerus ashmeadi and the “New Association” Parasitoid G. tuberculifemur Attacking Eggs of Homalodisca vitripennis
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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.

© 2009 Entomological Society of America
Nicola Irvin, Javier Suarez-Espinoza, and Mark Hoddle "Functional Response of Gonatocerus ashmeadi and the “New Association” Parasitoid G. tuberculifemur Attacking Eggs of Homalodisca vitripennis," Environmental Entomology 38(6), 1634-1641, (1 December 2009). https://doi.org/10.1603/022.038.0616
Received: 18 August 2008; Accepted: 1 August 2009; Published: 1 December 2009
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