Tri-trophic interactions--------------------------- --return

herbivore: Euura lasiolepis (Hymenoptera:Tenthredinidae)

parasitoid: Lathrostizus euurae(Hymenoptera:Ichneumonidae)

host plant: Salix lasiolepis (Salicaceae)



image copyrighted by J. Itami

Euura lasiolepis
Forms galls on on S. lasiolepis. Females show an extremely strong preference for high quality shoot sites on the willow that will provide the best surival for their offspring. The high precision in this preference perfromance relationship extends to the sawfly's ability to put female offspring in the highest quality sites and males in lower quality sites.

A Strong Relationship Between Oviposition Preference and Larval Performance in a Shoot-Galling Sawfly
Timothy P. Craig, Joanne K. Itami, and Peter W. Price
Ecology: Vol. 70, No. 6, pp. 1691–1699.

Resource Regulation by a Stem-Galling Sawfly on the Arroyo Willow.
Timothy P. Craig, Peter W. Price,Joanne K. Itami
Ecology: Vol. 67, No. 2, pp. 419–425.

Craig, T. P., P. W. Price and J. K. Itami. 1992 Facultative sex ratio shifts in response to host plant quality in an herbivorous insect. Oecologia 92:153-161.

Craig, T. P., and S. Mopper. 1992. Sex ratio variation in sawflies. Pages 61-92 in, M.R. Wagner and K.F. Raffa, editors. Sawfly adaptations to woody plants. Academic Press, New York

Craig, T.P., J.K. Itami and P.W. Price. 1990. Intraspecific competition and facilitation by a shoot-galling sawfly. Journal of Animal Ecology 59: 147-159

Craig, T. P., P. W. Price, K. M. Clancy, G. L. Waring and C. F. Sacchi. 1988. Forces preventing coevolution in the three-trophic-level system: willow, a gall-forming herbivore, and parasitoid. Pages 57-80, in K. C. Spencer, editor. Chemical Mediation of Coevolution, Academic Press, New York

Price, P. W., N. Cobb, T. P. Craig, G. W. Fernandes, J. K. Itami, S. Mopper and R. W. Preszler. 1990. Insect herbivore population dynamics on trees and shrubs: new approaches relevant to latent and eruptive species and life table development. Pages 1-38 in E. A. Bernays, editor. Focus on Insect-Plant Interactions. Volume 2, CRC Press, Boca Raton

Price, P. W., G. L. Waring, R. Julkunen-Titto, J. Tahvanainen, H. A. Mooney and T. P. Craig. 1989. The carbon/nutrient balance hypothesis in within species phytochemical variation of Salix lasiolepis. Journal of Chemical Ecology 15:1117-1131

Sacchi, C. F., P. W. Price, T. P. Craig and J. K. Itami. 1988. Impact of shoot galler attack on sexual reproduction in the arroyo willow. Ecology 69:2021-2030.

Price, P. W. and T. P. Craig. 1984. Life history, phenology, and survivorship of a stem-galling sawfly, Euura lasiolepis (Hymenoptera: Tenthredinidae), on the arroyo willow, Salix lasiolepis, in Northern Arizona. Annals of the Entomological Society of America 77:712-719.

Clancy, K. M., P. W. Price and T. P. Craig. 1986. Life history and natural enemies of an undescribed sawfly near Pontania pacifica (Hymenoptera: Tenthredinidae) that forms leaf galls on the arroyo willow, Salix lasiolepis. Annals of the Entomological Society of America 79:884-892


Arroyo Willow
Salix lasiolepis
Flagstaff, Arizona, USA

We studied the three-trophic interaction between a willow, sawfly, and parasitoids, examing both "bottom-up" effects originating from the willow and the "top-down" impact of the parasitoid on the interaction.


image copyrighted by J. Itami

Lathrostizus euurae
(Hymenoptera: Ichneumonidae)

The search time required to successfully attack a larva is long as can be seen by the many "firework" like ovipositor traces left by previous attemps to locate the larva in the large galls. Once a larve is located the prasitoid offspring is only successful if the egg is placed in the upper middle region of the sawfly larva where it can lie undetected by the sawfly larva's immune system.

The Window of Vulnerability of a Shoot-Galling Sawfly to Attack by a Parasitoid, Timothy P. Craig, Joanne K. Itami, and Peter W. Price
Ecology: Vol. 71, No. 4, pp. 1471–1482.