During its 5 (males) or 6 (females) larval instars Pontania pacifica Marlatt develops in a gall in the leaves of Salix lasiolepis Bentham. The last-instar larva molts into the prepupa, which emerges from the gall and drops to the ground where it spins the cocoon in which pupation occurs. The gall is the result of hyperplasia and hypertrophy of the mesophyll in the young leaves. This process is probably the response of the plant to mechanical destruction of the cells during oviposition by the sawfly, and to the specific action of the colleterial secretion injected into the wound with the egg. The presence of egg or larva is not essential for formation of a typical gall, whose size and shape depend on the growth rate of the leaf. The sawfly larva and the gall form the nucleus for a community composed of both entomophagous and phytophagous species. The ichneumonids Lathrostizus euurae (Ashmead) and Scambus vcsicarius cnurae (Ashmead) are parasitic on the sawfly larvae. The eurytomid Eurytoma sp. feeds as a larva on the gall tissues, but as a parameter in the population dynamics of the sawfly it has the effect of a parasitoid; Eurytoma sp. is parasitized by the pteromalid Habrocytus borrowi Girault. The cosmopterygid Batrachedra salicipomonella Clemens and the curculionid Anthonomus sycophanta Walsh are inquilines, feeding as larvae on the gall tissues and frequently destroying the gall inhabitant. B. salicipomonella is parasitized by a braconid, Chelonus (Microchelonus) sp., and by an ichneumonid, Pimplopterus sp. The development of the gall is described, and descriptions are given for various life-history stages of P. pacifica, L. euurae, S. v. euurae, B. salicipomonella, and A. sycophanta, together with observations on their biology.
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L. E. Caltagirone (1964) studied this question.