DOI
https://doi.org/10.1086/343879

Summary
This publication deals with the analysis of nutrient content patterns (nitrogen and phosphorus) between insect herbivores and predators where the latter are found to exhibit on average 15% greater nitrogen content than herbivores.
Among herbivores, the evidence that recently derived lineages (e.g., herbivorous Diptera and Lepidoptera) have, on a relative basis, 15%–25% less body nitrogen than more ancient herbivore lineages. This paved the way to the elaboration of 5 different hypotheses in order to explain the origin of differences in nitrogen content between trophic levels and among phylogenetic lineages.

Relevance for Complex Systems Knowledge
The paper suggests the re-examination of the influence of basic nutrients on major features of insect evolution.
One of the hypotheses proposes that those herbivores, that adapted to a limited Nitrogen content, may enjoy an increase in mean individual fitness that in turn can result in an increased rate of speciation, a lowered rate of extinction or both.

Point of Strength
Using what at the time (2002) was a recently compiled database on insect nutrient content, they study 152 insect species. On this basis they start an important theoretical and mathematical discussion on the importance of the C:N ratio for herbivores and predators.