If the Phylogenetic Constraints Hypothesis applies to many species of sawflies, then it is likely to work in equivalent ways on other gall-inducing taxa. Even endophytic species, involving placement of an egg into plant tissue but without gall induction, may well evolve with equivalent constraints, adaptive syndromes, and emergent properties. These kinds of species are the subject of this chapter. We expect the species to be gall inducers or otherwise endophytic, to have life history traits consistent with the Phylogenetic Constraints Hypothesis, to respond positively and strongly to shoot length and or general plant vigor, and to be relatively uncommon or rare, patchily distributed, with latent population dynamics.

These groups offer the chance to test the Phylogenetic Constraints Hypothesis with independent taxa, and to test repeatedly. Broadening the comparative front in the search for general patterns in nature is the next logical step after moving from a focal species (Chapters 3 and 4) to its related species (Chapter 5).

Oviposition by insects into plant tissues is a relatively common trait, having evolved many times in strongly divergent phylogenetic lineages. Coupled with this behavior is the potential for the evolution of gall formation. This is because a female probes plant tissue to place the egg and uses lubricants from specific glands to ease the egg's passage through a narrow and often elongated egg canal in the ovipositor.